RAILWAYMANAGEMENTANDENGINEERING

TothememoryofmyfatherAristide

RailwayManagementandEngineeringFourthEdition

V.A.PROFILLIDISSectionofTransportation,DemocritusThraceUniversity,Greece

©V.A.Profillidis2014FourthrevisededitionAllrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans,electronic,mechanical,photocopying,recordingorotherwisewithoutthepriorpermissionofthepublisherV.A.ProfillidishasassertedhisrightundertheCopyright,DesignandPatentsAct,1988,tobeidentifiedastheauthorofthiswork.

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Profillidis,V.A.(VassiliosA.)RailwayManagementandEngineering/byV.A.Profillidis.--Fourth

edition.pagescm

Includesbibliographicalreferencesandindex.1.Railroadengineering.2.Railroads–Management.I.Title.TF145.P762014385.068–dc232013037783

ISBN9781409464631(hbk)ISBN9781472407788(ebk-ePUB)

Contents

ForewordbyProf.A.LópezPitaPreface

1.RailwaysandTransport

1.1.Evolutionofrailways1.1.1.Historicaloutline1.1.2.Thegoldenageofrailwaysandrecenttechnicalinnovations1.1.3.Railwaysandothercompetingtransportationmeans1.1.4.Railwaysintheeraofmonopolyandcompetition

1.2.Characteristicsofrailtransport1.2.1.Abilitytotransporthighvolumes1.2.2.Energyconsumption1.2.3.Environmentalimpactandsafety

1.3.Economicgrowthandrailways1.4.Increaseofmobilityandrailways1.5.Railpassengertraffic

1.5.1.Volumesofrailpassengertraffic1.5.2.Shareofrailwaysinthepassengermarket1.5.3.Growthratesofrailpassengertraffic1.5.4.Distanceswithacomparativeadvantageforrailpassengertraffic

1.6.Railfreighttraffic1.6.1.Volumesofrailfreighttraffic1.6.2.Shareofrailwaysinthefreightmarket1.6.3.Growthratesofrailfreighttraffic

1.7.Railwaytraffic,lengthoflines,staffandproductivity1.8.Prioritytopassengerorfreighttraffic

1.9.Transportationserviceswithgoodprospectsfortherailways1.9.1.Comparativeadvantagesofrailwaysandhigh-speedtrains1.9.2.Urbanrailservices1.9.3.Combinedtransport1.9.4.Bulkloads1.9.5.Railfreighttransportandlogistics

1.10.Railandairtransport:Competitionorcomplementarity1.10.1.Areasofcompetitionandofcomplementarity1.10.2.Raillinkswithairports1.10.3.Railconnectionsofairportswithotherareas

1.11.Internationalrailwayinstitutions1.12.Rollingstockindustries1.13.Railwayinteroperability1.14.ApplicationsofGPSinrailways

2.HighSpeedsandMagneticLevitation

2.1.Theevolutionofhighspeedsonrails2.1.1.Definitionofhigh-speedtrainsandevolutionofspeed2.1.2.Panoramaofhigh-speedlinesaroundtheworld2.1.3.Highspeedsforonlypassengerormixedtraffic

2.2.High-speedtrainsandtheirimpactontherailmarket2.2.1.Highspeedsandpopulationconcentrations2.2.2.Impactofhighspeedsonthereductionofrailtraveltimes2.2.3.Highspeedsandnewrailtraffic

2.3.Technicalfeaturesofhigh-speedrailwaylines2.3.1.Technicalcharacteristicsofhigh-speedlines2.3.2.Trackcharacteristicsforhighspeeds2.3.3.Rollingstockforhighspeeds2.3.4.Powersupplyathighspeeds

2.4.TheChannelTunnelandhighspeedsbetweenLondonandParis2.4.1.Technicaldescription2.4.2.Traveltimes2.4.3.Methodoffinancingandforecastsofdemand

2.4.4.Operation,safetyandmaintenance2.5.Tiltingtrains2.6.Aerotrain2.7.Magneticlevitation

2.7.1.Technicaldescription2.7.2.Comparisonofmagneticlevitationwithconventionalrailways2.7.3.Applicationsofmagneticlevitation

3.PolicyandLegislation

3.1.Thecompetitiveinternationalenvironmentandtheevolutionoftheorganizationofrailways

3.2.Thedualnatureofrailways:businessandtechnology3.2.1.Weaknessesinheritedtorailways3.2.2.Comparativeadvantagesofrailways3.2.3.Strategyandrestructuringmeasures3.2.4.Railwaysandtransportrequirements

3.3.Globalizationandliberalizationoftherailmarket3.4.Separationofinfrastructurefromoperationandthenewchallengesfor

railways3.4.1.Separationasanincentiveforcompetition3.4.2.Competitionandnewchallengesforrailways3.4.3.Variousformsofseparation

3.5.Adefinitionofrailwayinfrastructure3.6.EuropeanUnionraillegislation3.7.Somerepresentativemodelsofseparationofinfrastructurefromoperationin

Europeanrailways3.7.1.TheIntegratedmodel3.7.2.TheSemi-integratedmodelwithapparentorganicseparation3.7.3.TheHoldingmodel3.7.4.TheSeparatedmodel3.7.5.TheSeparatedmodelalongwithfurtherseparationininfrastructure3.7.6.TheSeparatedmodelalongwithprivatization3.7.7.Assessmentofthevariousmodels

3.8.RaillegislationintheUSAandCanada3.9.RaillegislationinJapan3.10.RaillegislationinChinaandIndia3.11.RaillegislationinAustraliaandNewZealand

4.ForecastofRailDemand

4.1.Purposes,needsandmethodsfortheforecastofraildemand4.2.Parametersaffectingthevariouscategoriesofraildemand

4.2.1.Parametersaffectingraildemandglobally(aggregateapproach)4.2.2.Effectsondemandofthevariousparametersofrailtransport

4.2.2.1.Passengerraildemand4.2.2.2.Freightraildemand

4.3.Qualitativemethods4.3.1.Marketsurveys4.3.2.Scenariowritingmethod4.3.3.Delphimethod

4.4.Statisticalprojections4.4.1.Theoreticalbackgroundandconditionsofapplicability4.4.2.Exampleofastatisticalprojection

4.5.Econometricmodels4.5.1.Definitionanddomainsofapplication4.5.2.Statisticaltestsforthevalidityofaneconometricmodel4.5.3.Examplesofsomeeconometricmodels4.5.4.Exogenousandendogenousvariablesinraileconometricmodels

4.6.Gravitymodels4.7.Fuzzymodels

4.7.1.Descriptionofthefuzzymethod4.7.2.Exampleofafuzzymodel

4.8.Time-seriesmodels4.8.1.Definitionoftime-seriesmodels–ApproachofBox-Jenkins4.8.2.TheLeastmedianofsquares(LMS)methodfortheforecastofrail

demand4.9.Statisticalevaluationoftheforecastingabilityofamodel

4.10.Acomparativeanalysisofperformancesofeachmethod4.11.Modellingofrailfreightdemand

5.CostsandPricing

5.1.Definitionofrailwaycosts5.1.1.Constructionandoperationcosts5.1.2.Fixedandvariablecosts5.1.3.Marginalcost5.1.4.Externalcostsandmarginalsocialcost5.1.5.Generalizedcost

5.2.Constructioncostofanewrailwayline5.2.1.Factorsaffectingrailconstructioncost5.2.2.Constructioncostsfornewhigh-speedlines5.2.3.Allocationofcoststothevariousrailcomponents5.2.4.Constructioncostsofcivilengineeringworks5.2.5.Constructioncostsoftrack5.2.6.Constructioncostsofelectrictraction5.2.7.Constructioncostsofsignaling

5.3.Maintenanceandoperationcostsofinfrastructure5.3.1.Maintenancecostofinfrastructure5.3.2.Operationcostofinfrastructure

5.4.Costofpurchaseofrollingstock5.4.1.Costofhigh-speedrollingstock5.4.2.Costofordinarypassengervehicles5.4.3.Costoffreightvehicles5.4.4.Costofdiesellocomotives5.4.5.Costofelectriclocomotives

5.5.Economiclifeofthevariouscomponentsoftherailwaysystem5.6.Costofoperationofarailwaycompany

5.6.1.Passengertransport5.6.2.Freighttransport5.6.3.Combinedtransport

5.7.Quantificationofexternaleffectsinmonetaryvalues

5.8.Pricingofinfrastructure5.8.1.Principlesofinfrastructurepricing5.8.2.Objectivesofinfrastructurepricing5.8.3.Financialconsequencesofinfrastructurepricing5.8.4.Acommercialapproachofinfrastructurepricing5.8.5.Theoreticalandpracticalinfrastructurepricing5.8.6.Structureofinfrastructurepricing

5.9.Infrastructurepricingmodelsinsomecountries5.9.1.InfrastructurepricingaccordingtoEuropeanUnionlegislation5.9.2.France5.9.3.Germany5.9.4.UnitedKingdom5.9.5.SwedenandFinland5.9.6.Italy5.9.7.Switzerland5.9.8.Othercountries5.9.9.Acomparisonofrailinfrastructurecharges

5.10.Pricingofoperation5.10.1.Targetsofpricingofoperation5.10.2.Thetraditionalmethodofpricing5.10.3.Effectsofelasticities5.10.4.Pricingandcompetition

5.11.Pricingofpassengertraffic5.11.1.Theexistence(ornot)ofpublicserviceobligations5.11.2.Thestrategicdilemma:profitorincreaseoftraffic5.11.3.Pricingforrailoperatorswithoutpublicserviceobligations5.11.4.Yieldmanagementtechniques5.11.5.Complementarycommercialmeasurestoincreaserevenues

5.12.Pricingoffreighttraffic

6.PlanningandManagementofRailways

6.1.Railwaysandthesocialandeconomicenvironment6.1.1.Asystemsapproachfortherailways

6.1.2.Railwaysandthesocialandeconomicenvironment6.1.2.1.Thesocialandeconomicenvironment6.1.2.2.Strategicandtacticallevelofdecisions6.1.2.3.Separationinbusinessunits6.1.2.4.Changesandrequirementsoftheenvironmentofrailways

6.1.3.Qualitycontrol6.2.Competitionandimpactonrailwaymanagement6.3.Feasibilitystudiesandmethodsoffinancing

6.3.1.Needforevaluationofanyrailproject6.3.2.Benefitsandcostsfromnewrailwayinfrastructure6.3.3.Evaluationmethodsforrailprojects6.3.4.Methodsoffinancinganewrailproject6.3.5.Public-PrivatePartnerships

6.4.Planningtherailwayactivity6.4.1.Needandpurposesofplanning6.4.2.MasterPlansandBusinessPlans6.4.3.AbriefdescriptionofaBusinessPlanofarailwayundertaking

6.5.Projectmanagementforrailways6.5.1.Definitionofprojectmanagement6.5.2.Scope,benefitsandcostsofprojectmanagement6.5.3.Somerailprojectsthatcouldrequireprojectmanagement6.5.4.Adescriptionoftasksofprojectmanagementforrailways

6.6.Managementofinfrastructure6.6.1.Tasksandobjectivesforrailinfrastructure6.6.2.Anewmanagementapproach6.6.3.Theissueofoutsourcing6.6.4.Theneedforanhomogeneousrailproductattheworldlevel

6.7.Managementandpolicyforrailpassengertransport6.7.1.Tasksandobjectivesforrailpassengertransport6.7.2.Asegmentationoftraffic6.7.3.Anewstrategycombiningcompetition,cooperationandalliances6.7.4.Traditionalweaknessesandofferofanewglobalproductofrailways6.7.5.Applicationofinformaticstechnologies(internet,SMS)

6.7.6.Marketing–Customersatisfactionsurveys–Creationofanewculture

6.8.Managementandpolicyforrailfreighttransport6.8.1.Tasksandobjectivesofrailfreighttransport6.8.2.Amercilesscompetition6.8.3.Integrationofrailfreightinthelogisticschain

6.9.Humanresourcesandtheirrevalorization6.9.1.Theneedforamoreentrepreneurialapproach6.9.2.Allocationofhumanresources6.9.3.Theartofmotivatingpeopletowork6.9.4.Increaseofproductivity6.9.5.Restructuringandrevalorizationofhumanresources

6.10.Privatizationofrailways6.10.1.Prerequisitesandtargetsofprivatization6.10.2.Privatizationandcompetition6.10.3.Theproblemofdebt6.10.4.TheneedforastrongRegulator6.10.5.Privatizationofinfrastructure6.10.6.Privatizationofoperation6.10.7.Somecasesofprivatizationofrailwaysallovertheworld6.10.8.Effectsanddegreeofprivatization

6.11.Justificationandcalculationofpublicserviceobligations

7.TheTrackSystem

7.1.Thetraditionaldivisionofrailwaytopicsintotrack,tractionandoperation7.2.Thetracksystemanditscomponents7.3.Trackonballastoronconcreteslab7.4.Trackgauge7.5.Axleloadandtrafficload

7.5.1.Axleload7.5.2.Trafficload

7.6.Sleeperspacing7.7.Thewheel-railcontact

7.8.Transversewheeloscillationsalongtherail7.9.Railinclinationonsleeper7.10.Loadinggauge

7.10.1.Staticanddynamicloadinggauge7.10.2.European,BritishandAmericanloadinggauge7.10.3.Loadinggaugeforhigh-speedtracks7.10.4.Loadinggaugeformetrosystems7.10.5.Loadinggaugeformetricgaugetracks

7.11.Forcesgeneratedbythemovementofarailvehicle–Staticanddynamicanalysis7.11.1.Forcesgenerated7.11.2.Staticanddynamicanalysis-Trackdefectsandadditionaldynamic

loads7.12.Influenceofforcesonpassengercomfort

8.MechanicalBehaviorofTrack

8.1.Avarietyofmethodsadjustedtothenatureoftheproblemunderstudy8.2.TrackcoefficientsandBousinesq’sanalysis

8.2.1.Definitions–Symbols8.2.2.Trackcoefficients8.2.3.TrackcoefficientsandBousinesq’sanalysis

8.3.Approximateuni-directionalelasticanalysisofverticaleffects8.3.1.Assumptionsandformulas8.3.2.Resultsofthemethod

8.4.Accurateanalysisofthemechanicalbehavioroftrack–Finiteelementmethodandelastoplasticanalysis8.4.1.Ashortdescriptionofapplicationsofthefiniteelementmethodin

trackproblems8.4.2.Constructionofthemeshofthemodel8.4.3.Limitconditions8.4.4.Stress-strainrelationship

8.4.4.1.Caseofballastandsubgrade8.4.4.2.Caseofrailandsleeper

8.4.5.Numericalcalculations8.4.6.Determinationofthemechanicalcharacteristicsofthevarious

materials8.4.7.Stressandstraininthetrack-subgradesystem8.4.8.Distributionofwheelloadalongsuccessivesleepers8.4.9.Elasticlineofsleeper

8.5.Dynamicanalysisofthetrack-subgradesystem8.6.Trackdefectsandadditionaldynamicloads8.7.Dynamicimpactfactorcoefficient8.8.Designofthetrack-subgradesystem8.9.Vibrationsandnoisefromrailtraffic

8.9.1.Originsofrailvibrations8.9.2.Relationofrailnoiseleveltospeed8.9.3.Dampingofrailnoiseinrelationtodistance8.9.4.Noiselevelinrelationtoinfrastructuretype8.9.5.Noiselevelsinhighspeeds8.9.6.Noiselevelstandards

8.10.Analysisoftheaccuratemechanicalbehaviorofrail8.11.Applicationofunilateralcontacttheoriesinrailwayproblems

8.11.1.Transmissionofforcesthroughcontactsurfaces8.11.2.Unilateralcontacttheories8.11.3.Equationsoftheunilateralcontactproblem8.11.4.Numericalcalculations

9.Subgrade–GeotechnicalandHydrogeologicalAnalysis

9.1.Theimportanceoftherailwaysubgradeontrackqualityanditsfunctions9.2.Analyticalgeotechnicalstudy

9.2.1.Targetsofageotechnicalstudyandsoilinvestigation9.2.2.Preliminarystudies9.2.3.Techniquesandmethodsofexplorationusedinageotechnicalstudy9.2.4.Planningtheexplorationprogram9.2.5.Geotechnicalreportandlongitudinalsection

9.3.Geotechnicalclassificationsofsoils

9.4.Hydrogeologicalconditions9.5.Classificationoftherailwaysubgrade9.6.Mechanicalcharacteristicsofthesubgrade9.7.Theformationlayer

9.7.1.Layingofformationlayerinnewtracks9.7.2.Improvementofformationlayerinexistingtracks

9.8.Impactoftrafficloadonthesubgrade9.9.Impactofmaintenanceconditionsonthesubgrade

9.9.1.Themaintenancecoefficient9.9.2.Impactofthemaintenancecoefficientonthebehavioroftrackbed

andthesubgrade9.9.3.Impactofthemaintenancecoefficientonsubgradestresses

9.10.Fatiguebehaviorofthesubgrade9.11.Frostprotectionofrailwaysubgrades

9.11.1.Frostindex9.11.2.Frostfoundationthickness9.11.3.Frostprotectionmethodsonexistingtracks

9.12.Tracksubgradeincutsandonembankments–Valuesofslopes9.12.1.Subgradeincutsections9.12.2.Subgradeonembankmentsections

9.13.Thereinforcedsoiltechnique9.14.Hydraulicanalysisandcalculationofflows

9.14.1.Levelofgroundwater9.14.2.Semi-empiricalformulasforthecalculationofrun-offflows9.14.3.Therationalmethodforthecalculationofrun-offflows

9.15.Geotextilesinrailwaysubgrades9.15.1.Characteristics,typesandpropertiesofgeotextiles9.15.2.Useandapplicationsofgeotextilesintherailwaysubgrade

9.16.Vegetationonthesubgradeandtheballast9.16.1.Vegetationonthetrackandherbicides9.16.2.Criteriaanddosageforapplicationofherbicides

9.17.Earthquakesandthebehavioroftrackandthesubgrade

10.TheRail

10.1.Railprofiles10.2.Manufacturingofrailsteel10.3.Mechanicalstrengthandchemicalcompositionofrailsteel

10.3.1.Mechanicalstrength10.3.2.Chemical

composition10.3.2.1.Carbon10.3.2.2.Manganese10.3.2.3.ChromiumandSilicon10.3.2.4.Chromium–Manganese10.3.2.5.Equivalentcarbonpercentage

10.3.3.Railgrades10.3.3.1.RailgradesaccordingtoUIC10.3.3.2.RailgradesaccordingtoEuropeanstandard10.3.3.3.Choiceofrailgrade

10.4.Choiceofrailprofile10.4.1.Standardgaugetracks10.4.2.Metricgaugetracks10.4.3.Broadgaugetracks10.4.4.Geometricalcharacteristicsofvariousrailprofiles

10.5.Transportofrails10.6.Analysisofstressesintherail

10.6.1.Stressesatwheel-railcontact10.6.2.Bendingstressesoftherailontheballast10.6.3.Bendingstressesoftherailheadontherailweb10.6.4.Stressescausedbytemperaturechanges10.6.5.Plasticstresses

10.7.Analysisofthemechanicalbehaviorofrailbythefiniteelementandthephotoelasticitymethods

10.8.Railfatigue10.8.1.Fatiguecurveandraillifetimedetermination10.8.2.Railfatiguecriterion

10.8.3.Evolutionofaninternaldiscontinuity10.9.Raildefects

10.9.1.Definitionofraildefects10.9.2.Codificationofraildefects10.9.3.Defectsinrailends

10.9.3.1.Longitudinalverticalcracking10.9.4.Defectsawayfromrailends

10.9.4.1.Tacheovale10.9.4.2.Horizontalcracking10.9.4.3.Rolling(running)surfacedisintegration10.9.4.4.Short-pitchcorrugations10.9.4.5.Long-pitchcorrugations10.9.4.6.Lateralwear10.9.4.7.Shellingoftherunningsurface10.9.4.8.Gauge-cornershelling

10.9.5.Defectscausedbyraildamage10.9.5.1.Bruising10.9.5.2.Faultymachining

10.9.6.Weldingandresurfacingdefects10.9.6.1.Electricflash-buttwelding10.9.6.2.Thermitweldingandelectricarcweldingdefects

10.10.Permissiblerailwear10.10.1.Verticalwear10.10.2.Lateralwear

10.11.Optimumlifetimeofrail10.12.Fishplates10.13.Thecontinuousweldedrail

10.13.1.Thecontinuousweldingtechnique10.13.2.Mechanicalbehaviorofcontinuousweldedrail

10.13.2.1.Assumptions10.13.2.2.Simplifiedmechanicalanalysisofcontinuouswelded

rail10.13.2.3.Distributionofforcesalongacontinuousweldedrail

10.13.2.4.Lengthchangesintheexpansionzone10.13.2.5.Railwelding

10.13.2.5.1.Flash-buttwelding10.13.2.5.2.Thermitwelding10.13.2.5.3.Electricarcwelding

10.13.2.6.Distressingofacontinuousweldedrail10.13.3.Expansiondevices10.13.4.Advantagesofthecontinuousweldedrail

11.Sleepers–Fastenings

11.1.Thevarioustypesofsleepersandtheirfunctions11.2.Steelsleepers

11.2.1.Formandproperties11.2.2.Dimensions,weightandchemicalcomposition11.2.3.Advantagesanddisadvantages11.2.4.Lifetime

11.3.Timbersleepers11.3.1.Form,propertiesandtimbertypes11.3.2.Geometricalcharacteristics11.3.3.Advantagesanddisadvantages11.3.4.Lifetime11.3.5.Deformabilityoftimbersleepers

11.4.Concretesleepers11.4.1.Inherentweaknessesofconcretesleepers11.4.2.Thetwotypesofconcretesleepers

11.5.Thetwin-blockreinforced-concretesleeper11.5.1.Geometricalcharacteristicsandmechanicalstrength11.5.2.Advantagesanddisadvantages11.5.3.Lifetime11.5.4.Deformabilityoftwin-blocksleepers

11.6.Themonoblockprestressed-concretesleeper11.6.1.Geometricalcharacteristicsandmechanicalstrength11.6.2.Advantagesanddisadvantages

11.6.3.Lifetime11.6.4.Deformabilityofmonoblocksleepers11.6.5.Monoblocksleepersinhigh-speedtracks

11.7.Manufacturing,qualitycontrolandtestingofconcretesleepers11.8.Stressesdevelopingbeneaththesleeper11.9.Fastenings

11.9.1.Functionalcharacteristics11.9.2.Typesoffastenings

11.9.2.1.Rigidfastenings11.9.2.2.Elasticfastenings11.9.2.3.Typesofelasticfastenings11.9.2.4.Operatingprinciplesofelasticfastenings

11.9.3.Forcesandstressesinrigidandinelasticfastenings11.9.4.Designcriteria,anchorageandinsulationofafastening11.9.5.Railcreepandanti-creepanchors

11.10.Resilientpads11.10.1.Padswithorwithoutabaseplate11.10.2.Functionsandpropertiesofpads11.10.3.Dimensions,materialsanddesign11.10.4.Force-elongationcurves

11.11.RequirementsoftheEuropeanspecificationsforthesleeper-fasteningsystem

11.12.Numericalapplicationforthedesignofthevarioustrackcomponents

12.Ballast

12.1.Functionsofballastandsubballast12.1.1.Functionsofballast12.1.2.Functionsofsubballast

12.2.Geometricalcharacteristicsofballast12.2.1.Granulometriccomposition12.2.2.Fineparticles12.2.3.Fines12.2.4.Particleshape

12.2.4.1.Flakinessindex12.2.4.2.Shapeindex12.2.4.3.Particlelength

12.3.Mechanicalbehaviorofballastandsubballast12.3.1.Elastoplasticbehavior12.3.2.Fatiguebehavior

12.3.2.1.Ballast12.3.2.2.Subballast

12.3.3.Modulusofelasticity12.3.3.1.Ballast12.3.3.2.Subballast

12.4.Ballasthardness12.4.1.TheDevaltest12.4.2.TheLosAngelestest12.4.3.TheMicrodevaltest12.4.4.Requiredstrengthandhardnessofballast

12.5.Determinationoftheappropriatethicknessofballast12.5.1.Determinationoftheappropriatethicknessoftrackbed12.5.2.Requiredthicknessoftrackbed(ballast+subballast)toavoidfrost

penetration12.5.3.Thicknessofballastandsubballast12.5.4.CalculationofthicknessofballastaccordingtotheBritish

regulations12.5.5.Numericalapplication12.5.6.Appropriatethicknessofballastformetricgaugetracks

12.6.Trackcross-sections12.7.Lifetimeandre-useofballast

13.TransverseEffects–Derailment

13.1.Transverseeffects13.2.Transversetrackforces

13.2.1.Transversestaticforce13.2.2.Transversedynamicforce

13.3.Transversetrackresistance13.4.Influenceofballastcharacteristicsontransversetrackresistance

13.4.1.Influenceofthegeometricalcharacteristicsoftheballastcross-section

13.4.2.Influenceofthegranulometriccompositionofballast13.4.3.Influenceofthedegreeofballastcompacting

13.5.Influenceofsleepertypeontransversetrackresistance13.6.Additionalmeasuresandspecialequipmentusedtoincreasetransverse

trackresistance13.7.Derailment

13.7.1.Derailmentcausedbytrackshifting13.7.2.Derailmentcausedbywheelclimbingontherail13.7.3.Derailmentcausedbytheoverturningofthevehicle13.7.4.Derailmentsafetyfactor–Numericalapplication

13.8.Effectsoftransversewinds

14.TrackLayout

14.1.Railvehiclerunningonacurve14.1.1.Effectsduringmovementofarailvehicleonacurve14.1.2.Transitioncurve–Cubicparabolaorclothoid

14.2.Theoreticalandactualvaluesofcant–Permissiblevaluesoftransverseacceleration14.2.1.Theoreticalvalueofcantforcompletecompensationofcentrifugal

forces14.2.2.Appliedvalueofcant,cantdeficiencyandcantexcess14.2.3.Cantdeficiencyandtiltingtrains14.2.4.Permissiblevaluesoftransverseacceleration14.2.5.Variationintimeofcantdeficiency

14.3.Limitvaluesofcant,cantdeficiency,cantexcessandnon-compensatedtransverseacceleration14.3.1.LimitvaluesaccordingtoUIC14.3.2.LimitvaluesaccordingtoEuropeanspecifications14.3.3.Geometricalcharacteristicsoflayoutinsomehigh-speedtracks

14.4.Calculationofthetransitioncurve

14.5.Calculationofthecirculararc14.6.Caseofconsecutivesamesenseandantisensecirculararcs14.7.Superelevationramp14.8.Combiningmaximumandminimumspeeds14.9.Relationshipoftrainspeedwithradiusofcurvature14.10.Transitioncurvesinthecaseofvariationofthedistancebetweentheaxes

oftwotracks14.11.Longitudinalgradientsandverticaltransitioncurves

14.11.1.Longitudinalgradients14.11.2.Verticaltransitioncurves

14.12.Someconsiderationsformetricgaugetracks14.13.Layoutdesignwiththeuseoftablesandcomputermethods14.14.Constructionofanewrailwayline

14.14.1.Feasibilitystudy14.14.2.Preliminarydesign14.14.3.Outlinedesign14.14.4.Finaldesign14.14.5.Stakingofthetracklayout

14.15.Environmentalaspectsoftracklayout

15.SwitchesandCrossings

15.1.Functionsofswitchesandcrossings15.2.Componentsofaturnout15.3.Variousformsofturnouts15.4.Runningspeedonturnouts15.5.Geometricalcharacteristicsofturnouts15.6.Derailmentcriterionforswitchesandcrossings15.7.Turnoutsonacurvedmaintrack15.8.Turnoutsrunwithincreasedspeeds15.9.Sleeperandtracklayoutinturnoutsandcrossings15.10.Manualandautomaticoperationofturnouts15.11.Designprinciplesforswitchesandcrossings

16.LayingandMaintenanceofTrack

16.1.Layingoftrack16.1.1.Mechanicalequipment16.1.2.Sequenceofconstructionofthevarioustrackworks

16.2.Trackmaintenanceandparametersinfluencingit16.3.Definitionsandparametersassociatedwithtrackdefects16.4.Trackdefects

16.4.1.Longitudinaldefect16.4.2.Transversedefect16.4.3.Horizontaldefect16.4.4.Trackgauge16.4.5.Tracktwist

16.5.Recordingmethodsoftrackdefects16.6.Limitvaluesoftrackdefects

16.6.1.Limitvaluesforhigh-,rapid-andmedium-speedtracks16.6.2.Limitvaluesformedium-andlow-speedtracks16.6.3.Acceptancevalues16.6.4.Emergencyvalues16.6.5.LimitvaluesaccordingtoEuropeanspecifications

16.7.Progressoftrackdefects16.7.1.Longitudinaldefect

16.7.1.1.Meansettlementoftrack16.7.1.2.Standarddeviationoflongitudinaldefects16.7.1.3.Intervalbetweenmaintenancesessions

16.7.2.Transversedefect16.7.3.Horizontaldefect16.7.4.Gaugedeviations16.7.5.Tracktwist

16.8.Mechanicalequipmentformaintenanceworks16.9.Schedulingofmaintenanceoperations16.10.Technicalconsiderationsfortrackmaintenanceworks16.11.Optimizationofmaintenanceexpenses16.12.Trackmaintenance,vegetationandweedcontrol

17.SlabTrack

17.1.Thedilemmabetweenballastedandnon-ballastedtrack17.1.1.Advantagesandweaknessesofballastedtrack17.1.2.Thenon-ballastedtrack17.1.3.Firsttrials,testsandevolutionofslabtracktechniques

17.2.Mechanicalbehaviorofslabtrack17.2.1.Simulationofslabtrack17.2.2.Stressesandsettlementsinthecaseofslabtrack

17.3.Avarietyofformsofnon-ballastedtrack17.4.Slabtrackwithsleepers

17.4.1.TheRhedatechnique17.4.2.TheZüblintechnique17.4.3.TheStedeftechnique

17.5.Slabtrackwithoutsleepers17.6.Non-ballastedtrackonanasphaltlayer17.7.Transitionbetweenballastedandslabtrack17.8.Costsofslabtrack

18.TrainDynamics

18.1.Traintraction18.2.Resistancesactingduringtrainmotion18.3.RunningresistanceRL

18.3.1.Generalequationfortherunningresistance18.3.2.Empiricalformulasofsomerailwaysfortherunningresistance

18.3.2.1.FormulasoftheFrenchrailways18.3.2.1.1.Dieselorelectriclocomotives18.3.2.1.2.Hauledrollingstock18.3.2.1.3.Electricpassengervehicles

18.3.2.2.FormulaoftheAmericanrailways18.3.2.3.FormulasoftheGermanrailways18.3.2.4.Formulasforbroadandmetricgaugerailways

18.3.3.Resistancesdevelopedwhenrunninginatunnel

18.3.3.1.Pressureproblems18.3.3.2.Increasedaerodynamicresistancesintunnels18.3.3.3.Crossingoftrains18.3.3.4.Tunnelcross-sectionrequirementsathighspeeds

18.3.4.Comparativerunningresistancebetweenrailwaysandroadvehicles18.4.ResistanceRcduetotrackcurves18.5.ResistanceRgcausedbygravity18.6.Inertial(acceleration)resistanceRin

18.7.Startingforceandtractionforceofatrain18.8.Adhesionforces18.9.Requiredtrainpower18.10.Valuesoftrainaccelerationanddeceleration18.11.Trainbraking

18.11.1.Brakingsystems18.11.2.Brakingdistance18.11.3.Europeanspecificationsconcerningbraking

19.RollingStock

19.1.Componentsofrailvehicle19.2.Wheels

19.2.1.Geometricalcharacteristicsandmaterials19.2.2.Wheeldefectsandreprofiling19.2.3.Lifecycleofawheel

19.3.Axles19.4.Bogies

19.4.1.Definitionandfunctionsofabogie19.4.2.Formsofbogies19.4.3.Componentsofabogie19.4.4.Self-steeringbogie

19.5.Springs19.6.Couplingsandbuffers19.7.Designofrollingstock

19.8.LocalizationofthepositionofarailvehiclewiththeuseofGPS19.9.Tiltingtrains

19.9.1.Needswhichgaverisetothetiltingtechnology19.9.2.Tiltingtechnology19.9.3.Technicalandoperationalcharacteristicsoftiltingtrains19.9.4.Reductionsintraveltimesbytiltingtrains19.9.5.Costoftiltingtrains

20.DieselandElectricTraction

20.1.Thevarioustractionsystems20.2.Steamtraction

20.2.1.Operatingprincipleofthesteamengine20.2.2.Mainpartsofasteamlocomotive20.2.3.Disadvantagesandabandonmentofthesteamlocomotive

20.3.Fromsteamtractiontodieseltractionandelectrictraction20.3.1.Fromsteamtractiontodieseltraction20.3.2.Fromsteamtractiontoelectrictraction20.3.3.Gasturbinelocomotives

20.4.Dieseltraction20.4.1.Operatingprincipleofthedieselengine20.4.2.Transmissionsystems20.4.3.Requirementsofdiesellocomotives20.4.4.Advantagesanddisadvantagesofdieseltraction

20.5.Electrictractionanditssubsystems20.5.1.Powersupplysubsystem20.5.2.Tractionsubsystem20.5.3.Requirementsandpriorities

20.6.Electrictractionsystems20.6.1.Directcurrenttraction20.6.2.Alternatingcurrenttraction

20.6.2.1.Alternatingcurrenttractionat15,000V,16⅔Hz20.6.2.2.Alternatingcurrenttractionat25,000V,50Hz

20.6.3.Advantagesanddisadvantagesofelectrictractioncomparedto

dieseltraction20.7.Feasibilityanalysisbeforeelectrification

20.7.1.Feasibilityanalysisparametersandprocedure20.7.2.Criterionforselectionofthelinestobeelectrified

20.8.Overheadcontactsystem20.8.1.Partsandcomponentsoftheoverheadcontactsystem20.8.2.Calculationofthecharacteristicsofthecontactwirewiththeuseof

physicalmodels20.8.3.Calculationofthecontactwirewiththeuseofthefiniteelement

method20.8.4.Suspensionofoverheadcontactsystems20.8.5.Thepantograph20.8.6.Powertransmissionbyconductorrail20.8.7.Electricalandpowercharacteristicsofsomehigh-speedtracks

20.9.Overheadlinesupportingpoles20.9.1.Polematerial20.9.2.Polespacing20.9.3.Polefoundation

20.10.Substations20.10.1.Substationsfeedingdirectcurrentsystems20.10.2.Substationsfeedingalternatingcurrentsystems20.10.3.Fromthyristorsto‘gateturnoff’technology20.10.4.Operatingcontrolcenter20.10.5.Interferenceofelectrictractionwithtelecommunicationand

signalingsystems20.11.Synchronousandasynchronousmotors20.12.Electriclocomotivesmaintenance–Depot

21.Signaling—Safety—Interoperability

21.1.Functionsofsignaling21.1.1.Evolutionofsignaling21.1.2.Brakingdistanceandsignalingrequirements21.1.3.Trafficsafetyandregularity

21.1.4.Theregulatoryframework21.1.5.Basicsignalingfunctions

21.2.Semaphoresignaling21.2.1.Visualandaudiblesignals21.2.2.Colorsusedinsignals21.2.3.Typesofsignals

21.3.Operatingprinciplesoflightsignaling–Thetrackcircuit21.3.1.Definitionoflightsignaling21.3.2.Thetrackcircuit

21.3.2.1.Definition21.3.2.2.Operatingprincipleofthetrackcircuit21.3.2.3.Theblocksection21.3.2.4.Typesoftrackcircuits21.3.2.5.Trackcircuitrelay

21.4.Equipmentandpartsofalightsignalingsystem21.4.1.Lightsignals21.4.2.Switchcontroldevices21.4.3.Trainintegritydetectors21.4.4.Approachlockingdetectors21.4.5.Localoperatinganddisplayboard21.4.6.Remotemonitoringandcontrol

21.4.6.1.Operatingprinciples21.4.6.2.Equipment21.4.6.3.Remotemonitoring–Controloftrafficsafety

21.4.7.Powersupplyequipment21.5.Trainrunningprocedureinalightsignalingsystem

21.5.1.Routeinterlock21.5.2.Singletrackinterlock21.5.3.Approachinterlock21.5.4.Interlockingofoppositeschedules21.5.5.Freewayinterlocking21.5.6.Lightsignalinterlocking21.5.7.Compatibleandincompatibleschedules

21.6.Speedcontrol21.6.1.Thevariousspeedcontrolsystems

21.6.1.1.Automaticcontrolanddriverfunctions21.6.1.2.Intermittentspeedcontrol21.6.1.3.Continuousspeedcontrol21.6.1.4.Speedcontrolandinteroperability

21.6.2.Technicalcharacteristicsoftrainspeedcontrolsystems21.6.2.1.Electromechanicalcontrol21.6.2.2.Track-locomotivecontinuouscommunicationsystem

21.7.Trainscheduling21.8.Calculationofthecapacityofatrack21.9.Interoperability

21.9.1.Definition21.9.2.Interoperabilityoftrackgauges21.9.3.Interoperabilityofpowersystems21.9.4.TheEuropeanRailTrafficManagementSystem(ERTMS)

21.10.Safetymeasuresatlevelcrossings21.11.Managingrailwaysafety

22.EnvironmentalEffectsofRailways

22.1.Climatechange,thetransportsectorandsustainabledevelopment22.1.1.Climatechange22.1.2.Sustainabledevelopment22.1.3.Transportandtheenvironment

22.2.Airpollutionandrailways22.2.1.Airpollutantsfromrailwaysandothertransportmodes22.2.2.ThegreenhouseeffectandCO2emissionsfromrailwaysandother

transportmodes22.2.3.CO2emissionsbythevarioustypesoftrains22.2.4.Carbontax,internalizationofexternalcostsandrailways

22.3.Railwaynoise22.3.1.Sourcesanddampingofrailwaynoise22.3.2.Noiseindicatorsandmaximumpermittedlevelofrailnoise

22.3.3.Measuresforreductionofrailnoiseandrelatedcosts22.4.Energyconsumptionandrailways

22.4.1.Energyconsumptionandthetransportsector22.4.2.Energyconsumptionwithinthetransportsector22.4.3.Energyconsumptionfordieselandelectrictraction22.4.4.Specificenergyconsumptionofrailwaysandothertransportmodes

22.5.Energyconsumedinrailwaysforcomfortfunctions22.6.Accidents,safetyandrailways

22.6.1.Definitionofrailwayaccidents22.6.2.Typesofrailwayaccidents22.6.3.Causesofrailwayaccidents22.6.4.Measurestoincreaserailwaysafety22.6.5.Evolutioninthenumberofrailwayaccidents22.6.6.Accidentswhentransportinghazardousmaterials22.6.7.Railwayaccidentsandsafetycertification

22.7.Landoccupancy,landscape22.8.Congestion

ListofReferencesAbbreviationsIndex

Forewordby

Prof.A.LópezPitaCataloniaPolytechnicUniversityMemberoftheSpanishRoyalAcademyofEngineering

Thepublicationin2006ofthebookRailwayManagementandEngineering,byProfessorProfillidis,waswithoutdoubtaninspireddecision.IncomparisonwithhispreviouspublicationRailwayEngineering,whichappearedinthenineties,itmeanttheinclusionofamoreglobalvisionoftherailwayasamodeoftransport.

Sevenyearshavepassedsincetheadoption,byProfessorProfillidis,oftheaforementionedvisioninhispublicationandhenowpresentsuswithaneweditionofhissuccessfulbook.Tobeabletoproduceanappropriateforewordforthecontentofthisbook,Ihavetakenthelibertyofanalyzingtheexistingdifferencesbetweenthe2006editionandthenewone.

TheconclusionIhavereached,aftercarryingouttheaforementionedcomparison,isthatthestrongpointsofthepreviousversionareconfirmedanditsmoreconcisesectionshavebeenthoroughlystrengthened.Asaresult,ProfessorProfillidis’workdeservesourrecognition.

Iwouldliketohighlight,inthecontextofthepositiveassessmentofthepublication,theattentionpaidtodealinginmoredepthwithrailwayandtransport,withitsownchapter.Byknowingonlytheframeofreference,onecanmakesignificantadvances.Intheaforementionedchapterthelatestavailablestatisticaldataareincluded,afactthatenablesustobetterappreciatetheprogressmadeinrecentyears,inaspectsaskeyasenergycosts.

Inthetimeswelivein,itisnowevenmorenecessarytoincludethefinancialaspectsthatdominatetherailwaybusinessinthedecisionmakingprocess.Formanyyearscivilengineershavepaidpreferentialattentiontothesolvingoftechnicalproblems,forgetting,atleastinpart,thefinancialcomponent.

ThatiswhythebookbyProfessorProfillidiswillenablereaderstohave,injustonepublication,anaccountofrailwaytechnologyontheonehandand

managementofthecommercialandfinancialoperationontheother.Tomyknowledge,thereisnobookthatoffersthisdualperspectiveinEnglishtechnicalliterature.

FinallyIwouldliketohighlightthetreatmentgiveninthebook’sfinalchapterconcerningtheeffectsoftherailwayontheenvironment.Withregardtothepreviousedition,thecontenthasbeenthoroughlyimproved,somuchsothatwecantrulyspeakofitasanewedition.Atatimeofspecialawarenessandconcernabouttheenvironment,inthebroadestsense,payinggreaterattentiontotheseaspectsis,withoutdoubt,averywisechoice.

Therefore,IwillconcludebythankingProfessorProfillidisforhavingmadethisnewpublicationavailabletotheuniversityandprofessionalcommunity.Itisusefulbothforthosewhoaretakinganinterestintherailwayasamodeoftransportforthefirsttimeandforthoseprofessionalswhowishtoupdatetheirknowledge.

Iamconvincedthatreadersofthisbookwillbesatisfiednotonlybyitscontentbutalsobytheclaritywithwhichithasbeenwritten.

Preface

Inarapidlychangingworld,withincreasingcompetitioninallsectorsoftransportation,railwaysareinaperiodofrestructuringtheirmanagementandtechnology.Asnewmethodsoforganizationareintroducedandcommercialandtariffpolicieschangeradically,amoreentrepreneurialspiritisrequired.Atthesametime,newhigh-speedtracksarebeingconstructedandoldtracksrenewed;high-comfortrollingstockvehiclesarebeingintroduced,logisticsandcombinedtransportarebeingdeveloped.Awarenessofenvironmentalissues,dailyhighwayandairportcongestionandsearchforgreatersafetygiverailwaysanewrolewithinthetransportationsystem.Indeed,railwaysoperatein20111,028,723kilometersoflinesworldwide(ofwhich272,447kilometersareelectrified),withabout7millionrailwayemployeesandtransport31.47billionpassengers(2,885billionpassenger-kms)and11.36billiontons(9,669billionton-kms)offreight.

Meanwhile,methodsofanalysishavesignificantlyevolved,principallyduetocomputerapplications,newtechnologicalachievementsandnewwaysofthinkingandapproachingoldproblems.

Thus,ithasbecomenecessarytocomeupwithanewscientificapproachtotacklemanagementandengineeringaspectsofrailways,tounderstandin-depththecausesandconsequencesofthevarioussituationsandphenomenaandtosuggesttheappropriatemethodsandsolutionstosolvethevariousemergingproblems.

Thisfourtheditionofthebookaimstocovertheneedforanewscientificapproachforrailways.Itisintendedtobeofusetorailwaymanagers,economistsandengineers,consultingeconomistsandengineers,andstudentsofschoolsofengineering,transportationandmanagement.

Thiswiderangeofintendedreadershiphasledmetodividethebookinthreedistinctparts.

Thefirstsixchaptersdealwiththemanagementofrailwaysandmoreparticularlywithissuesrelatedtothepositionofrailwaysinthetransportsector,newtechnologicalachievementssuchashigh-speedandmagneticlevitationtrains,policyandlegislationforrailways,methodsofforecastofraildemand,costsandeconomicsofrailways,methodsofpricing,managementofrailways,

andtheseparationofinfrastructurefromoperation.Thenextelevenchaptersdealwiththetrackandmoreparticularlywith

issuesrelatedtothemechanicalbehavioranddesignofthetracksystemandofitsvariouscomponents(rails,sleepers,ballastsubgrade),tracklayout,transverseeffectsandderailment,switchesandcrossings,layingandmaintenanceoftrack,andslabtrack.

Thelastfivechaptersdealwithrollingstock,signalingandenvironmentaltopicsandmoreparticularlywithissuesrelatedtotraindynamics,railtunnels,designandoperationofrollingstock,dieselandelectrictraction,signalingandsafety,interoperability,railtrafficmanagementsystem,andtheenvironmentaleffectsofrailways.

Eachchapterofthebookcontainsthenecessarytheoreticalanalysisofthetopicsstudied,therecommendedsolutions,applications,chartsanddesignofthespecificrailwaycomponent.Inthisway,therequirementforatheoreticalanalysisismetandtheneedsoftherailwaymanagerandengineerfortables,nomographs,regulations,etc.aresatisfiedaswell.

RailwaysinEuropehaveseparatedactivitiesofinfrastructurefromthoseofoperation.Inotherpartsoftheworld,however,railwaysremainunified.Thebookaddressesbothsituations(separatedandunifiedrailways).

Railwayspresentgreatdifferencesintheirtechnologies.Somethingmaybevalidforonesuchtechnology,butnotforanother.Toovercomethisproblem,standards,specificationsandregulationsoftheInternationalUnionofRailways(UIC)andoftheEuropeanCommissionhavebeenusedtothegreatestextentpossible.Wheneveraspecifictechnologyormethodispresented,thelimitsofitsapplicationareclearlyemphasized.

Ihavetriedtotakeintoaccountthemostrecentscientificandstatisticaldata,availableasofspring2013.Butintheeraoftheinternetandofalmostimmediateinformationforeverythingchangingintheworld,thereaderofthebookisaffordedwithallsourcesofinformation,sothathecanupdateandadaptthecontentofthebooktohisneeds.

IwouldliketoexpressmythankstoDr.G.Botzorisforhistechnicalassistance.

Thewritingofabookneedsalotoftime,whichisusuallytakenfromfamilyactivities.Iwouldliketothankmywifeandsonfortheirunderstandingandpatience.

Authorsaim,invain,tocreateaperfectbook.However,insciencenothingispermanentandeverythingisevolvingrapidly.Thus,Iwillwelcometheviewsandcommentsofreaders.

V.A.Profillidis

1RailwaysandTransport

1.1.Evolutionofrailways

1.1.1.Historicaloutline

Sincethedawnofhumanactivitytothisday,quickandsafetransportationofpeopleandgoodshasbeenaconstantgoalofeveryorganizedsociety.Itisgenerallyacknowledgedthatthefundamentalinnovationsinthedevelopmentoftransportationincludedthediscoveryofthewheel(about3000B.C.),navigation(about3000B.C.inNilesriverinEgypt,about2000B.C.intheseabyPhoenicians),therailway,theautomobileandtheairplane.Railways,intheirpresentform,madetheirappearanceatthebeginningofthe19thcenturyinBritishmines.Theirmaincharacteristicistheguidedmovementofthewheelbythetrackthroughametal-to-metalcontact.

However,theforerunnersoftherailwaysofourtimeappearedmuchearlierthanthe19thcentury.Movementofcarriagesorwagonsonmetalguidesisillustratedina1550gravurefoundinBasel,Switzerland,whichshowstransportationmethodsemployedintheminesofAlsace.TheguidedmovementofcarriagesingeneralwasalreadyknowninRomantimes,aswitnessedbygroovescarvedonthestonepavementtofacilitateandspeedupthemovementofcarriages.

OnMountPentelinearAthens,fromwherethewhitemarbleoftheParthenonandotherclassicalmonumentsoriginated,deepgroovesintherockygroundstillbeartestimonytothemethodsemployedbyancientGreekstomovemarbleslabstotheconstructionsites.Furthermore,theguidedmovementofcarriageswasappliedinGreekantiquitybylayingwoodenchannelsondirtroadstoguidecarts.Twochannelswereadequatefortheneedsofthedaytoaccommodateonecarriage.Whentwocarriagescamefacetoface,theyoungerdriverwouldmakewayfortheolderone.Itwassuggestedthatinsuchanencounter,Oedipusrefusedtomakewayandkilledtheoldercartdrivercomingfromtheoppositedirection,beingunawarethatitwashisfatherLaïus.

1.1.2.Thegoldenageofrailwaysandrecenttechnicalinnovations

Thedevelopmentofrailwayswasdecisivelyinfluencedbythefirstindustrialrevolution,theintroductionofsteampowerandtheextensiveexploitationofcoalandironmines.ThefirstrailwaylinesbeganoperatinginmostEuropeancountriesaround1830andrailwaynetworksattainedmaximumdensityatthebeginningofthe20thcentury.Afactorcontributingtothemassivegrowthoftherailwayswashighspeed(bythestandardsofthetime),whichenabledfastconnections.Steam-poweredengineshadalreadyachieved(intestruns)impressiveperformances:125km/hin1850inGreatBritain,145km/hin1895inFrance,210km/hin1903inGermany.Althoughmaximumoperatingspeedsweremuchlower(1/2to2/3oftestspeeds),theycontributedtotherapidgrowthofrailtransportation.

Theadoptionofelectrictraction,intheearly20thcentury,permittedafurtherdevelopmentofrailways,whiletheapplicationofsignalingandautomatictraincontrolinthe1950sfacilitatedtheoperationandincreasedcarryingcapacityofrailways.Majortechnologicalinnovationsduringthelastfivedecadesdrasticallychangedrailwayservices.Theseinnovationsinclude,amongothers,highspeedtrains,applicationsofGeographicPositioningSystems(GPS)andIntelligenceTechniques(IT),technicalinnovationsforthereductionofcostsandinteroperabilitytechniquestotackleincompatibilitiesbetweenthevariousrailwaytechnologies.

Paralleltoadvancesintechnology,innovationsinsofterforms,suchasorganization,management,costs,andsupplyofserviceshavepermittedtherailwaystoimprovetheircompetitivepositioninthetransportmarket.

1.1.3.Railwaysandothercompetingtransportationmeans

Timeshavechanged,however,andwhatwasimpressiveintheearly20thcentury,soonbecamelessandlesssatisfactory.Airplanes,passengercars,busesandtruckswerealreadyofferingtransportationalternativesateveryscale.Giventhepressureofcompetition,railwayshadtomodernizeandimprove,especiallyasregardsspeed,reductionofcosts,betterorganization,andimprovementoftheservicesoffered.Hence,wecometotheeraofhighspeedtrains(seechapter2)operatingat250÷320km/h(aspeedof574.8km/hwasattainedbyFrenchhighspeedtrainsin2001intestruns),combinedtransport(combinedrail-roadtransportation),high-volumetransportforbothpassengers(commuterservices)andfreight(bulkloads);thusattheseconddecadeofthe21stcentury,railwaysfacenewchallenges,(9),(13),(15)*.

Nevertheless,inparallelwithconventionalrailways(basedonmetal-to-metalcontact),experimentalresearchhasproceededsincethemid-1970swithtechniques,which,althoughusingguidedvehicletransport(likerailways),avoidanycontactbetweenthemovingvehicleandthebearinginfrastructure.Thesearetheaerotrainandthemagneticlevitationsystems,ormaglevs,which,intestruns,haveattainedspeedsof430km/hfortheaerotrainin1974and581km/hforthemaglevin2003.However,since2004magneticlevitationsystemshavebeenappliedandoperateataspeedof431km/h,(seealsosections2.6,2.7).

Thedevelopmentofrailwayshasbeenstimulatedbythegeneraleconomicactivity,whichmakesclearthreeeconomiccyclesatworldlevel,(Fig.1.1.),(26).

Fig.1.1.Economiccyclesandtransporttechnologies,(26)

1.1.4.Railwaysintheeraofmonopolyandcompetition

Railwaysplayedacatalyticroleinthefirstindustrialrevolutionafter1850andhavebeeninmostcasesdevelopedbyprivatecompanies,whichbuilt(andowned)therailwayinfrastructuretheyoperated,whileatthesametimeprovidingtheappropriaterollingstockandpersonnel.However,returnsinrailwayinvestmentswerelowerthanexpectedandimportantdeficitssoonappeared.Asrailwayshadacriticalpositionfortheeconomyandsecurityofeachcountry,manygovernmentshavenationalizedtheirrailwayssince1935.Thus,railwaysbecameastatemonopoly,whichhadasapositiveeffectthe

integratedrailwayservicesatthestatelevelandasnegativeeffectstheinflexibilityandpooradaptationtotheevolvingrequirementsoftheeconomyandsociety,(27).

Insomepartsoftheworld(particularlyinEuropeandtheUSA),state-ownedrailwayshavehadafter1950adecliningshareinthetransportmarket,(seesections1.5,1.6).Asameasuretostopandreversethissituation,theintroductionofintra-modalcompetitionhasbeenconsidered,namely,theoperationofmanyrailwaycompaniesonthesameroute.Insomecountries,liketheUSA,arailwaycompanykeptonowninginfrastructure,whileatthesametimeanotherrailwaycompanyhadtherighttorunonitsinfrastructurebypayingappropriatecharges.InEuropeancountries,however,theintroductionofintra-modalcompetitionwasrelatedtotheso-calledseparationofinfrastructurefromoperation,soastoensurefairandimpartialconditionsamongthemanyrailoperatorseventuallycompetingonthesameroute.Somecountries(amongthemtheUnitedKingdom,Japan,Canada,etc.)haveprivatizedpartsorthewholeoftheirrailwayactivities,(seealsosections3.4,6.10),(15),(20),(29).

1.2.Characteristicsofrailtransport

1.2.1.Abilitytotransporthighvolumes

Themaincharacteristicofrailtransportinvolvesitscapabilitytojoinseveralunitsintotrains.Theheaviesttrainsintheworldarefreighttrainstransportingbulkcommoditiessuchascoal,iron,cereals,etc.Indeed,freighttrainsof14,000*tons**withmultiplecouplingsareuseddailyintheUSA,whileinAustraliatrainstransportingmineralproductsexceed32,000tons,inChina20,000tons,inCanada20,700tons.Withregardtopassengers,railwaysarecapableoftransportingagreatnumberofpeople.HighspeedtrainsoftheJapaneserailwayshavetransported520,000passengersbetweenTokyoandOsakainonedayandregularlyabout370,000peoplebetweenthesetwocities(adistanceof515km).

Anothercharacteristicofrailtransportisitsonedegreeoffreedom,incomparisontoroadtransport,whichhastwodegreesoffreedom.Theonedegreeoffreedommakesdoor-to-doortransportationimpossibleforrail,butfavorslarge-scaleuseofautomaticcontrols,computersandelectronics.Asaresult,unittransportationcapacityofrailwaysishigh,e.g.commutertrainscantransport60,000passengersperhourandperdirection,(28),(30).

1.2.2.Energyconsumption

Railtransportischaracterizedbytheguidedmovementofwheelsontracksthroughthemetal-to-metalcontact,whichconsiderablyreducesrollingresistancetolessthan3kgpertoncarried.Accordingly,forthesamepropulsionforce,railvehiclescarryamuchlargerloadthanroadvehicles.Asaresult,railtransportconsumesonethirdasmuchenergyasroadtransportforthesametraffic.Thecomparisonbecomesmoredefinitivewithairplanes,whichconsumeforthesametraffic5÷7timesmoreenergythanrailways.

Theinterestsofprivatecompaniesandgroupshavenotpermittedtakingthefactorofenergyconsumptionintransportpoliciesintoaccountuntilnow.However,oilreservesallovertheworldcansatisfyneedsforamaximumoftwogenerationsfromnowonwards,(Fig1.2),andtheyhavebeenstimulatedbylowoilpricesfortwodecades(1983÷2003),ascomparedtopreviousyears,(Fig.1.3).Inanycase,theremainingyearsforwhichoilreservescansatisfyhumanneedsarecalculatedontoday’sratesofconsumption,withoutbeingabletoforecastaccuratelythecomingneedsinthefarfutureofemergingeconomies,likeChina,India,Brazilandothers.Worldoildemandwasin201288.03millionbarrelsperdayandisestimatedtoreach109.7millionbarrelsperdayin2035,(11).

Fig.1.2.Oilreservesallovertheworld,(compiledfromdataof(11))

Fig.1.3.EvolutionofpricesofoilinUSdollars(valuesoftheyear2013)from1862to2012,(compiledfromdataof(11))

1.2.3.Environmentalimpactandsafety

Anotheradvantageofrailtransportisitsmuchlowerenvironmentalpollution.Electrictrainsproducenoemissions,whilediesel-poweredtrainsgeneratemuchlesspollutionthanautomobilesforthesametraffic.ConcerningCO2emissions,railpassengertransportcausesforthesametraffic1/2CO2emissionscomparedtoroadpassengertransportand1/5comparedtoairtransport.EmissionsofCO2

ofrailfreightare1/4.5comparedtoroadand1/4comparedtoinlandwaterways,(17),(23).

Peopleallovertheworldhavebecomemoresensitiveabouttransportsafety.Forthesametraffic,theriskofafatalityoccurringisseventimesgreaterinroadthaninrailtransport,(23).Railwayperformanceisgenuinelyimpressive.

Finally,landoccupationperpassenger-kilometerorton-kilometerismuchlessforrailtransportthanforothertransportmodesandspecifically2÷3timeslessthanforroadtransport.Forthepurposesofcomparisonwithairplanes,itisnoteworthytomentionthatthehighspeedParis-Lyonsline(adistanceof427km)occupiesasmuchspaceastheParisairportatRoissy.

1.3.Economicgrowthandrailways

Itisestablished(Fig.1.4)thattheevolutionoftransportactivityasawholeisatapproximatelythesamerateastheevolutionoftheGrossDomesticProduct(GDP).AirtransportratesaregreaterthanGDPrates(almostdouble),whereasrailtransportratesaremuchslower,(2),(4),(13).Thealmostcontinuouslyupwardtendencyofbothpassengerandfreightforfivedecadesafter1950was

stoppedinEuropebytheeconomiccrisisof2008÷2012,whichaffectedprincipallysomeEuropeanUnion(EU)countries,(Fig.1.4).

Fig.1.4.Treofliving,accompaniedndsinthepassengertraffic(passenger-kms),thefreighttraffic(ton-kms)inrelationtotheGrossDomesticProductinthe15EUcountries*,(2)

1.4.Increaseofmobilityandrailways

Aconsiderableincreaseinthemobilityofindividualshasbeenmanifestedduringthelastsixdecades.Thenumberoftripsincreasedgreatly,mainlyasaresultof:–thepopulationincrease,–theincreaseinthestandardofliving,accompaniedbyanincreaseoftheprivatecarownershipindex.Theaveragevalueofthisindexforthe15EUcountrieswasin19701privatecarper5.21inhabitantsanditreachedin2010avalueof1privatecarper1.98inhabitants,(Fig.1.5).Theprivatecarownershipindexisdirectlyrelatedtopercapitanationalproduct,butnotproportionally,sinceitisinfluencedbythedevelopmentofthevarioustransportmodesforeachcountry,byitsgeographicalposition,etc.,

–thegradualreductionoftheimportanceofborders,aresultoftheglobalizationoftheeconomy.

Fig.1.5.Averageprivatecarownershipindexinthe15and27(numbersbetweenparentheses)EUcountries,(2)

Railtransportdidnotbenefit,incomparisontoothertransportmodes,fromthemobilityincreaseinrecentdecades.Thereasonsforthisstagnationofrailtransportaremainlyfocusedonthefollowingadvantagesofroadtransport,(16):

–door-to-doortransport,–highercomfort,–flexibility,–improvementoftheimageofprivatecars(asaresultofsystematicmarketingandpromotionefforts).

Onlyduringthe1980sandmainlythe1990sdidtherailwaysbegintoprovidesolutionswhichcouldcompetesomeoftheaboveadvantagesofroadtransport.

1.5.Railpassengertraffic

1.5.1.Volumesofrailpassengertraffic

Figure1.6illustratesrailpassengertraffic*forvariousgeographicalareasandcountriesoftheworld.Indeed,fourcountries(India,China,Japan,Russia)andtheEuropeanUnion(27countries)represent89.7%oftotalrailwaypassengertrafficallovertheworld,(1),(6).

Fig.1.6.Railwaypassengertrafficinvariousgeographicalareasandcountriesoftheworld(2010),(1),(6)

Figure1.7illustratesrailpassengertrafficinthe15and27EUcountriesincomparisonwithothertransportmodes.Hereafter,inthefigureswhichpresenttrafficdata,thenumbersgivenbetweenparenthesesrefertothe27EUcountries,whereasallothernumbersrefertothe15EUcountries.Fortheperiod1970÷2010andforthe15EUcountries,passengercarsincreasedtheirtrafficby161%,airplanesby1,333%,busesby55%andrailwaysby64%,(2).

Fig.1.7.Evolutionofpassengertrafficforvarioustransportmodesinthe15and27(numbersbetweenparentheses)EUcountries,(2)

1.5.2.Shareofrailwaysinthepassengermarket

Shareofrailwaysinthenationaltransportmarketforeachcountrydependsmainlyonthedegreetowhichtherailwaysmeettherequirementsofthemarketandthesociety,aswellasonthedegreeandorientationofstateinterventionandpolicyconcerningcompetition,tariffsandsubsidies.

Shareofrailwaysintheirnationaltransportmarketwasin2010asfollows,(Fig.1.8):36.9%forChina(against69.6%in1970),32.7%forRussia(against65%in1970),13.2%forIndia(against36%in1970),31.4%forJapan(against50.4%in1970),7.3%forthe15countriesoftheEU(against10.4%in1970),0.4%fortheUSA(against0.6%in1970),(2),(6),(13).

Figure1.9illustratestheevolutionofshareofrailwaysinthepassengermarketforthe15and27countriesoftheEU.Indeed,railwayshareintheEUpassengermarketwasaround50%in1950,butdroppedto10.4%in1970andto6.7%in2010,(2).

Figure1.10illustratesthedropofrailpassengershareintheUSAfromaround15%duringtheearly1950stolessthan0.6%after1970,(1),(6).

Fig.1.8.Shareofrailwaysinthenationalpassengermarketforseveralcountriesoftheworld(2010),(2),(6),(13)

Fig.1.9.Evolutionofshareinpassengertrafficforvarioustransportmodesinthe15and27(figuresbetweenparentheses)EUcountries,(2)

Fig.1.10.EvolutionofshareofvarioustransportmodesinthepassengermarketintheUSA,(1),(6)

1.5.3.Growthratesofrailpassengertraffic

Growthratesfortheperiod1970÷2007wereasfollowsfortheprincipalcountrieswithahighrailwaypassengertraffic:China:6.4%,India:5.2%,EU-15:2.0%,Japan:0.9%,Russia:0.3%,USA:0.2%,(Fig.1.11),(6),(13).

Fig.1.11.Growthrates(1970÷2007)ofrailpassengertrafficforsomecountries,(13)

1.5.4.Distanceswithacomparativeadvantageforrailpassengertraffic

Railwayshareisincreasedformediumdistances(150÷500km),forwhichrailwayshaveastrongcompetitiveadvantageinrelationtoairplanes,passengercars,andbuses,(Fig.1.12),(2).

Fig.1.12.Variationofshareinpassengertrafficformediumdistancesandforvarioustransportmodesinthe15EUcountries,(2)

Themediumdistancetraveledbyrailwaypassengerswasin2010524kmforChina,349kmfortheUSA,125kmforIndia,51kmfortheEU(15countries)

and28kmforJapan.EUcountriesandJapanhavelowtraveleddistancesduetothefactthatagreatpartofrailwaypassengerstravelinurbanorsuburbanareas,(1),(6),(13).

1.6.Railfreighttraffic

1.6.1.Volumesofrailfreighttraffic

Figure1.13illustratesrailfreighttrafficforvariousgeographicalareasandcountriesoftheworld.Indeed,sixcountries(USA,China,Russia,India,Canada,Ukraine)andtheEuropeanUnion(27countries)represent90.5%oftotalrailwaytrafficallovertheworld,(1),(6).

Fig.1.13.Railwayfreighttrafficinvariousgeographicalareasandcountriesoftheworld(2010),(1),(6)

AttheEuropeanlevel,Figure1.14illustratesrailfreighttrafficinthe15and27(numbersbetweenparentheses)EUcountries.CurrentlytherearenosignsintheEUforareversementandrecoveryfromthisdownwardtendencyinrailfreight.

Fig.1.14.Evolutionoffreighttrafficforvarioustransportmodesinthe15and27(numbersbetweenparentheses)EUcountries(2010),(2)

1.6.2.Shareofrailwaysinthefreightmarket

Figure1.15illustratestheevolutionoftheshareofrailwaysinthefreighttransportmarketforsomecountriesoftheworld,withahighshareintheUSAandalowoneinJapan.Highlevelsofrailwayfreightsharesreflecttheexistenceofhighvolumesofcommodityproductsinthespecificcountry,ahightraveleddistanceforrailfreight,appropriatenessofthespecificrailwaystocompetewithroadtrucksconcerningtariffs,capacityanddeliverytime.

Fig.1.15.Shareofrailwaysinthenationalfreightmarketforseveralcountriesoftheworld(2010),(2),(6),(13)

Figure1.16illustratestheevolutionoftheshareofrailwaysinthefreightmarketforthe15and27countriesoftheEU.Railwayfreightsharedroppedfrom20.0%in1970to8.2%in2010forthe15EUcountries,asmostEuropean

railwaysdidnotmanagetoefficientlymeettherequirementsoftheeconomy.ThesituationisinverseintheUSA,(Fig.1.17),whereafteradropbyhalfbetween1930and1970,railfreightsharehasstabilizedduringthelastfourdecadesaround40%with,however,increasingtendenciesduringrecentyears.

Fig.1.16.Evolutionofshareofrailfreighttrafficforvarioustransportmodesinthe15and27(numbersbetweenparentheses)EUcountries,(2)

Fig.1.17.EvolutionofrailshareinthefreighttransportmarketintheUSA,(1),(6)

1.6.3.Growthratesofrailfreighttraffic

Growthratesfortheperiod1970÷2007wereasfollowsfortheprincipalcountrieswithahighrailfreighttraffic:India:5.5%,China:5.3%,USA:2.2%,Russia:0.6%,EU-15:0.5%,Japan:-2.6%.

Fig.1.18.Growthrates(1970÷2007)ofrailfreighttrafficforsomecountries,(13)

1.7.Railwaytraffic,lengthoflines,staffandproductivity

Table1.1(nextpage)illustratesforseveralcountriesallovertheworldfortheyear2010,(1),(2),(6):•lengthofrailwaylines,•lengthofelectrifiedrailwaylines,•passengertraffic(inpassengersandpassenger-kilometers),•freighttraffic(intonsandton-kilometers),•staffnumbers,•railwayproductivity(inpassenger-kilometers+ton-kilometersperemployee).

1.8.Prioritytopassengerorfreighttraffic

Behindthenumbersofrailshareandtrafficpresentedinthepreviousparagraphs,abigdilemmaconcerningmanyrailwaysishidden:shouldrailwaysgivepriorityto(andthereforefacilitatethedevelopmentof)passengerorfreighttrains?Almostineverypartoftheworld,withtheexceptionoftheUSA,passengertrainshavebeengivenpriority(concerningdeparture-arrivaltimes,investment,etc.).Onthecontrary,intheUSA,thepriorityofrailwaysisfreighttraffic,withashareofabout42.6%in2010,whereasrailpassengertrafficisrathermarginalwithashareofabout0.4%,(1÷2generationsofAmericansnevertookatrainintheirlife).ShareofairtransportintheUSAwas11.5%in2010,thatofbuses2.9%,passengercars’share84.9%andmetros’share0.2%,(1),(2),(6).

WhilefreighttrafficvolumeswerestagnatinginEurope(seeFigure1.14),intheUSA,freighttrafficincreasedfrom1,000billiont-kmsin1970to2,469

billiont-kmsin2010,anumberthatshouldbecomparedtoavolumeof22.8billiont-kmsforFrenchrailwaysandavolumeof105.8billiont-kmsforGermanrailwaysfortheyear2010.

However,differencesofrailfreightshareintheUSAandEuropearealsoduetoanumberofotherreasons,(13),(14),(19):traveleddistancebyfreighttrainsintheUSA(1,476kmin2010)ismuchgreaterthaninEurope,Japan,etc.,freighttariffsintheUSAare1/2÷1/3ofmediumfreighttariffsinEurope,productivityintheUSArailfreightsectorincreasedfrom2millionton-kmsperemployeein1970(with566,000employeesintotalatthattime)to14.6millionton-kmsperemployeein2010(withonly169,280employees),whichreflectsanincreaseofproductivityof630%in40years,statesubsidiesaregivenintheUSAonlyforregionalpassengertrafficandnotforfreight,whereasinmanypartsoftheworldrailwaysreceivesubsidiesnotonlyforpassengerbutalsoforfreighttraffic,

Table1.1Railwaytraffic,lengthoflines,staffandproductivityinseveralcountriesall

overtheworldfortheyear2010,(1),(2),(6)

investmentintheUSAwasorientedtothefreightsector,with100billionUS

dollarsinvestedbetween1970÷2000inorderto,(19):–extendloadinggauge(seesection7.10),topermittwo-levelfreightwagonstransportingcontainerstoruntheAmericanrailnetwork,

–renewandinnovatefreightrollingstock,whilereducingbetween1970÷2000thetotalnumberoftractionmachinesby30%,wagonsby25%,andlinesinoperationby40%,

liberalizationofbothroadandrailtransportresultedinthereductionof30bigrailcompaniesin1970toonly8in2010,thusprovidingthepossibilityforeconomiesofscale,withtheexceptionoftheNorth-EastCorridor(NewYork-Boston),wheretherealpublicinterestistoavoidsaturationintheairportsofBoston,WashingtonandPhiladelphia,railwaylinesreceiveonlyfreighttrafficinalmosteveryotherplaceintheUSA.

Thus,thedisappearanceofpassengertrainsintheUSAgavefreighttrainsthepossibilitytobefullydevelopedwithoutanyrestrictionsandcutoffsconcerningdeparture–arrivaltimes.Wouldthisberealized,ifpassengertrainswerestilloperatingintheentireAmericanrailnetwork?Theansweristhatuntilacertainleveloffreightandpassengertraffic(whichisthecaseinthegreatmajorityofrailnetworksallovertheworld),freightandpassengertrainscancoexistwithoutmajorinconvenience.Forheavytrafficlines,however,authoritiesmustdecidewhethertheirpriorityispassengerorfreighttraffic,(14),(25).

1.9.Transportationserviceswithgoodprospectsfortherailways

1.9.1.Comparativeadvantagesofrailwaysandhighspeedtrains

Inacompetitivetransportmarket,railwaysshouldlookfortheircomparativeadvantages.Highspeeds(analyzedindetailinchapter2)areonesucharea.Otherareasincludeurbanrailservices,combinedtransport,aswellastransportationofbulkloadsand,finally,integratedserviceswhich,inadditiontotransportation,involvethecollection,storage,anddeliveryofgoods(logistics),(27),(29).

1.9.2.Urbanrailservices

Inaneraofexplodingtrafficproblems,railwayscandecisivelycontributetotheiralleviationthroughtheirlargecarryingcapacity,(Fig.1.19).Many

neglectedrailwaylinesconnectingcitycenterstothesuburbsareaccordinglybeingmodernizedandusedforurbanrailservices,thusrelievingthetrafficproblemsofmanycities,(28).

Fig.1.19.Carryingcapacityofvarioustransportsystems,(28),(34)

1.9.3.Combinedtransport

Thevarioustransportmodespresentcomparativeadvantagesconcerningtransportcostsinrelationtodistance,(Fig.1.20).Thus,forshortdistances,truckshaveacomparativeadvantage,forintermediatedistancesrailwayshaveanedge,whilegreatdistancesfavortheuseofships.Increasingcompetitionintheareaoffreighttransport,however,makesthesearchforthelowestcostcompulsory.Severalcountrieswithimportanttrucktransittraffic(AustriaandSwitzerland,amongothers)setstrictlimitstothenumberoftrucksintransit,soastoreducecongestionandsaturationontheroadnetwork.Finally,politicaleventsandconflictsmandatethesearchforalternative,reliableandsafetransportationroutes.Alltheabovehavecontributedtothedevelopmentofcombinedtransport.

Fig.1.20.Transportfreightcostsasarelationofdistance,forvarioustransportmodes,(16)

Combinedtransportmaybedefinedasacompositetransportationprocessinvolvingatleasttwoconsecutivetransportmodes(e.g.truck-ship,train-ship,truck-train).Twomaintechniquesweredevelopedforcombinedtransport:–Containers,usedinroad,rail,andseatransport.Thetendencyistousecontainersaslargeasitisallowedbytheexistingloadinggauge,(33).Externaldimensionsofcontainersareasfollows:•20’type:6.058mlongby2.438mwide,•40’type:12.192mlongby2.438mwide,•60’type:13.716mlongby2.438mwide.

–TheRo-Ro(Rollon-Rolloff)technique,wherebywholetrucksortruckbodieswithfreightareloadedonatrainorship,sothatonlyasmallpartofthetransportiscoveredbyroad.AccordingtoEUregulations,themaximumdimensionsoffreightvehiclesforcombinedtransportare:height4.0m,width2.5m,weight40tons.

Sincecombinedtransportrequirestransshipmentoffreightfromonemodetoanother(withassociatedexpenses),itisnecessarytodeterminetheminimumdistancebeyondwhichcombinedtransportbecomescost-effective.Theanswertothisquestionisnotsimple,sinceitdependsonthecostoflabor,energy,themechanicalequipmentfortransshipment,etc.Therefore,Europeanconditionsplacethisminimumdistanceat700÷900km,whereasintheUSAitissetat1,500km,(32),(35).

Thedevelopmentofcombinedtransportnecessitatestheexistenceofasatisfactorylevelinroadandrailnetworkandmoderntransshipmentequipment.Figure1.21illustratesthecostcomponentsforrail-roadcombinedtransportforeconomicconditionsofWesternEurope.

Fig.1.21.Costcomponentsforrail–roadcombinedtransportforeconomicconditionsofWesternEurope,(24),(35)

1.9.4.Bulkloads

Railwaysareveryadvantageousforbulkloadtransport,suchasrawmaterials,coal,petroleum,grainandotheragriculturalproducts.Railwaycompetitivenessinbulkloadtransportdepends,amongothermatters,uponthemarshallingyardsfacilities,wherefreighttrainsaredisassembledandreassembled,andwherelongand(often)unjustifiedwaitsareoccurring,(22).

1.9.5.Railfreighttransportandlogistics

Freighttransportbyrailwaslimiteduntilsomedecadesagotocarryinggoods.Thedynamicsofmoderntransport,however,havebroadenedthescopeofthetransportationprocess.Reliableandspeedycarriageisnolongersufficient.Itmustalsobeaccomplishedatthelowestpossiblecost,ensuringthatacertainquantityofgoodsbemadeavailableattherequiredplaceandtime.Animportantcontributiontothiseffecthasbeenachievedduringthelasttwodecadeswithso-calledlogistics,whichinvolvesthewholeprocessencompassingtimelyinformationontheneedtomakeavailableacertainitemataspecificplaceandtime,reliableandspeedytransport,possiblestorageandfinaldeliverytotherecipient,(Fig.1.22).Itisthereforeclearthatinthissensethetransportationprocesshasamuchbroadermeaning.

Fig.1.22.Fromsimplerailtransporttologistics,(16)

1.10.Railandairtransport:Competitionorcomplementarity

1.10.1.Areasofcompetitionandofcomplementarity

Fordistancesshorterthan500kmandwithtraveltimeslessthan3hours,railwayshaveanadvantageovertheairplane,sincetheyreachdirectlyintothecenterofservedcities.Ontheotherhand,fordistancesmorethan1,000km,theairplanehaspracticallynocompetitor,aseventhehighspeedtraincannottravel1,000km(withanumberofstopsinstations)inlessthan4h.

Fordistancesbetween500kmand1,000km,railandairtransportareincompetitionandtherailsharedependsontraveltime(comparedtoairplane),frequency,qualityofservice,etc,(Fig.1.23).

However,therearetwodomainswhererailwaysandairtransportcancooperatecomplementarily:raillinkstoairportsandmediumdistancerailconnectionsfromairportstoother(thantheservedcity)regions.

However,railandairtransportcannotworkandcooperateefficientlyunlessanumberofconditionsaremet,(5),(7):–physicalinterconnectionoftherailwaynetworkwiththeairport,whichmeans

thattherailwaystationreachestheairportwithdirectaccesstotheterminalandfacilitiesforthedisabled,

–coordinationoftherailwaytimetableswiththoseoftheairlinecompanies,–eventuallycombinedair/railticketswithlinkedfaresandsimultaneousreservations(i.e.integrationoftherailwayservicesintothecomputerizedairlinesystem),

–registrationofluggagerighttothefinaldestination,whichinvolvesovercomingthedifficultiesassociatedwithsafetycontrol.However,someairports(e.g.Heathrow,Gatwick,Madrid),whichhadremotebaggagecheck-infacilitieshavewithdrawnthese,whileFrankfurtairportstillofferssuchfacilities.

Fig.1.23.Railshare(fortheyear2011)forsomehighspeedroutes,inrelationtotraveltimeanddistance,(5)

1.10.2.Raillinkswithairports

Allmajorairportshaveefficientraillinkstothecenterofthecitiesserved.In2008,evenintheUSA,whererailwayshaveafairshareofpassengertransport,8ofthe20largestairportshaveraillinkstotheservedcities,withaverylowcostcomparedtotaxi,(5),(18).

1.10.3.Railconnectionsofairportswithotherareas

Inaneraofmercilesscompetitionamongairlinesandairportsaboutextending

theirhinterland,railways(andparticularlyhighspeedones),whichtakecustomersattheveryheartofconurbations,maybeadecisivefactorforanairportinwinningtrafficfromanothercityorregionthantheoneserveddirectlybytheairport,(7).

ThusBrusselscanbereachedthroughParis-CharlesdeGaulleairportbyhighspeedtrain.Similarly,throughFrankfurtairport,Cologne(in1h15min)andStuttgart(in1h30min)canbereachedbyhighspeedtrains.

Intheiraggressivecommercialapproach,theairlinesgivepreferencetolong-haulflights.Thusrailways(andparticularlyhighspeedones)canbecomeakeyelementfortheincreaseoftheairlinetrafficbyservingmedium-sizecities,whicharenotadequatelyservedbyairbutlieonaprincipalrailwayline.

1.11.Internationalrailwayinstitutions

Internationalrailwaycooperationisrealizedwithintheframeworkofthefollowinginternationalinstitutions:

1.11.1.TheInternationalUnionofRailways(UIC),whichwasestablishedin1922andhad205membersin2012,thesebeingrailauthoritiesfromvariouscountriesallovertheworld.ThegeneralobjectivesoftheUICare,(4),(15):•developmentofinternationalrailwaycooperationandtransactions,planningandimplementationofmeasurespermittingrailwayservicesacrossnationalbordersandensuringqualityinbothpassengerandfreighttraffic,

•standardizationanddesignoftechnicalspecificationsconcerningallcomponentsofrailwaytechnology(e.g.ballast,subgrade,electrification,etc.),

•informinginternationalorganizations,decisioncenters,andpublicopinionontheusefulnessandadvantagesoftransportbyrail.

Withinthisgeneralframework,UICactivitiescoverthefollowingsectors:allocatingincomeandoffsettingdebitbetweenrailwayoperators,planningtheoptimizationandrationalizationofthetechnicalequipment,exploitationmethods,dataprocessing,etc.,researchonnewtechnologicaladvancesconcerningtrack,rollingstock,etc.,statisticsandotherinformation.

1.11.2.TheEuropeanConferenceofMinistersofTransport(ECMT),whichhasbeenintegratedwithintheOrganizationforEconomicCooperationandDevelopment(OECD)since2004underthenameInternationalTransport

Forum(ITF).

1.11.3.TheCommunityofEuropeanRailwaysandInfrastructureCompanies(CER)oftheEuropeanUnionmember-countries,whichaimsatestablishingcommonpositionsandpoliciesofrailwaysinEuropeanUnionmember-countries.CountriesinaccesstotheEUandneighboringtotheEUcountriesalsoparticipateintheCER.

1.11.4.TheEuropeanInstituteofRailResearch(ERRI)knownalsowiththeinitialsOREofitsformerFrenchname(‘OrganismedesRecherchesetd’Essais’),whichisanagencyoftheInternationalUnionofRailwaysaimingtoorganizeandcoordinateresearchandtestprocedures,whichadvancerailwaytechnology.Topicsinvestigatedaredividedintothefollowingfivecategories(denotedbythelettersA,B,C,D,E):

A:Traction,signaling,telecommunications,B:Rollingstock,C:Interactionbetweenrollingstockandtrack,D:Track,bridges,tunnels,E:Materials’technology.

Forthedecade2010÷2020,majorresearchaxesofERRIfocusoninteroperability,GPSapplicationsforthemonitoringofvehicles(seesections1.14and19.8),reductionofcosts,reductionofrailnoise,improvementsinenergyconsumption,logistics,etc.

1.11.5.TheEuropeanRailwayAgency(ERA).Inordertopromotefurthercooperationintherailwaysectoramongthemember-countriesoftheEU,theEuropeanRailwayAgencyhasbeenestablishedtocarryoutthefollowingduties:coordinationofEuropeanrailwaysonissuesofsafety,interoperabilityandqualityofservice,establishingcommonpoliciesandstrategies.

1.12.Therailindustryworldwide

Therailindustrymayrefertothefollowingcomponentsoftherailwaysystem:-infrastructure(subgrade,subballast,ballast,sleepers,fastenings,rails,electrificationequipment),

-engineeringsystems(telecommunications,control/safety),-rollingstock(locomotives(dieselorelectric),passengervehicles,freightvehicles,highspeedvehicles,metrovehicles),

Shareofthesesegmentsintheworldwiderailmarketduringthelastdecadeisasfollows:infrastructure50%,rollingstock39%,andengineeringsystems11%.

Theworldrollingstockmarketwasestimatedat44.9billion€fortheyear2009(forecastfor2016:53.3billion€)withthefollowingshareoftheprincipalrollingstockconstructors:Bombardier(whichabsorbedABB):23%,Alstom(whichabsorbedFiatFerroviaria):14%,ChinaSouthLocomotive&RollingStockCorporation(CSR):14%,Siemens:11.5%,ChinaNorthLocomotiveandRollingStockIndustryCorporation(CNR):11%,GeneralElectric:7.5%,Kawasaki:5%,ConstruccionesyAuxiliardeFerrocarriles(Spain):5%,Transmashholding(Russia):4%,othercompanies:5%.

Shareofthevarioustypesofordersofrollingstockworldwidefortheyear2003wereasfollows:locomotives:37%,regionalandinterurbantrains:19%,commutertrains:19%,metros:13%,highspeedtrains:6%,tramways:6%.

However,followingtheexampleofAirbus,effortsbeganin1999foraclosercooperationofEuropeancompaniesinviewofaconstructionofahighspeedtraincombiningtheadvantagesoftheFrenchTGVandtheGermanICE(thirdgeneration),withsmallprogress,however,todate.

ThoughwesternEuropewasformanydecadesthemostsignificantmarketforrailindustryproducts,constructionduringrecentyearsofmanynewtracks(particularlyhighspeed)inChina,Korea,TaiwanandelsewhereandofnewmetrosystemsshiftedthecenterofinterestoftherailindustryfromWesternEuropeeastwards.

1.13.Railwayinteroperability

Therailwayindustryandrailwaycompanieshavetriedformanydecadesofstateprotectionismtopresentasmanydifferencesaspossibleintheirproducts.Thusagreatvarietyofgauges(seesection7.4),electrificationsystems(seesection20.6,Fig.20.4),signalingandtrafficcontrolsystems(seesection21.9,Table21.1),makeefficientrailwaycooperationdifficult.

Forinstance,atraincannothaveacontinuousroutefromLisbontoParisbecauseofthedifferenceofgauges,fromParistoAmsterdambecauseofincompatibilityofelectrificationsystems.However,afuture-orientedrail

transportsystem,suchasthatcurrentlytakingshapeinEuropeandothercontinents,shouldbreakfreeonceandforallfromnationalboundaries.Interoperability,initsstrictsense,ismeantasthetechnicalcompatibilitybetweentherailwayrollingstockortrackequipmentofdifferentcountriesorindustries.Principaltechnicalobstaclesthatinteroperabilitytriestotackleconcern:trackgauge,electrificationsystems,signalingsystems,loadinggaugeoftrains,platformheights,trainlength,axleloadandsystemsthatpertaintocommunication,control-commandandsafety,(21).

Butthegoalforrailwaysshouldbetooffertheircustomersanunbrokeninternationalservicemeetingthesamehighqualitystandardsthroughout,whateverthelengthofthejourneyorthenumberofcountriescrossed.Thus,inadditiontotheharmonizationoftechnicalsystems,interoperabilityshouldaimtosimilarlevelsofqualityofservice,introductionofmoreeasilyaccessiblepassengerandfreightinformationanddistributionsystemsforcustomersworldwide.

Interoperabilityisanalyzedinmoredetailinsection21.9.

1.14.ApplicationsofGPSinrailways

RailwaytechnologyandoperationwillbestronglyinfluencedbyevolutionsofelectronicsandtelematicssuchastheGeographicalInformationSystems(GIS)andtheGlobalPositioningSystem(GPS).Satellitessendoutsignsthatarereceivedonearthbytheappropriatereceivers,(Fig.1.24).Byreceivingasignsimultaneouslyfrom7÷8satelliteswecancalculatethepositionofarailvehiclewithanaccuracyof20÷30cm,itsspeedandthedirectionofmovement.Anumberofsatellitesareflyingoncircularmoveataheightof20,200kmwithaperiodofrotationof24h,insuchawaythatatleastfoursatellitesareatanymomentvisibleataspecificlocationontheearth.TherehavebeenmanyapplicationsofGPSintransportationsincesomeyears:intelligentvehiclehighwaysystemsintheUSA,followingofbusoperationandambulanceeventsinmanyEuropeancountries,accuratefollowingandmonitoringofrailwayvehicles(inusealreadybysomerailwayoperators,seealsosection19.8),etc.InspiredfromthesuccessofEurocontrol,theEuropeansystemofmanagementofairtraffic,internationalinstitutionssuchastheERAortheUICshouldaimtoinstallaninternationalsystemforthemanagementofrailwaytrafficandthecontinuousmonitoringofrailvehicles.

Fig.1.24.GPSapplicationsinrailways

*Figuresbetweenparenthesesdenotereferences,thelistofwhichisattheendofthebook.*UnitsconcerningthousandsanddecimalsarepresentedinthisbookaccordingtotheAmericansystem.Thus,comma(,)denotesthousandsandpoint(.)denotesdecimals.

**The‘ton’isaforceunitanddenotesaweightofamassof1,000kg.*15EuropeanUnioncountries:Austria,Belgium,Denmark,Finland,France,Germany,Greece,Ireland,Italy,Luxembourg,Netherlands,Portugal,Spain,Sweden,UnitedKingdom.

*Datapresentedinthisbookarethemostrecentonesinspring2013.Thereader,however,canupdatedatabyvisitingtheEUandUICinternetsites,whichare:-EuropeanUnion:http://europa.eu.int/-InternationalUnionofRailways:http://www.uic.asso.fr

2HighSpeedsandMagneticLevitation

2.1.Theevolutionofhighspeedsonrails

2.1.1.Definitionofhigh-speedtrainsandevolutionofspeed

High-speedtrains(HST)weretheresponseofrailwaystothetransportmarketrequirementforreducedtraveltimes.However,thereisnouniversallyacceptedtopspeed,beyondwhichasystemcanbecalledasHSTsystem.Ithasbeengenerallyacceptedthatexistingconventionalrailwaytechnology,withimprovementsinthetrackandrollingstock,canaccommodatetopspeedsofupto200km/h.Beyondthisspeed,additionalcapitalcostsareneededtomeettherequirementsofmorestringentdesignfeaturesandsophisticatedsystemcomponents.Thus,weconsiderHSTwhenV>200km/h.ThisbroaddefinitionofHSTisincludedintheEuropeanlegislation,amongothersinDirective49/1996.Highspeedswerepioneeredbytworailwaynetworks:–theJapaneserailways,withthe1964operationofthe“Shinkansen”high-speedlinebetweenTokyoandOsaka,withatopspeedof210km/h,increasedin1985to240km/handlaterupto300km/h,dependingonthesectionoftheline,

–theFrenchrailways,byoperatingtheTGV*high-speedtrainbetweenParisandLyonsin1981,withatopspeedof260km/h,increasedto270km/hin1983andto300km/hin1989.

Bothlineswerebuiltonheavilytraveledroutesshowingsignsofsaturation.Facedwithimprovingtheexistinginfrastructureorbuildinganewhigh-speedline,thelatterwasopted,(44),(47).

Figure2.1illustratestheevolutionofmaximumspeedoftrains,inoperationandintestruns.

Fig.2.1.Theevolutionofmaximumspeedofrailways

2.1.2.Panoramaofhigh-speedlinesaroundtheworld

High-speedlineswereconstructedfrom1964to2013inthefollowingcountries:•Japan(Tokyo-Osaka-Fukuoka-Kagoshima,Takasaki-Nagano,Tokyo-Aomori,Tokyo-Niigata),

•France(Paris-Lyons,Paris-Bordeaux,Paris-Marseille,Parris-Lille-Calais,Paris-Strasbourg),

•Germany(Hannover-Würzburg,Mannheim-Stuttgart,Hannover-Berlin,Aachen-Cologne-Frankfurt),

•Italy(Rome-Florence,Rome-Naples,Turin-Milan-Bologna-Florence),•Spain(Madrid-Barcelona,Madrid-Valladolid,Madrid-Cordoba-Seville,Cordoba-Malaga,Madrid-Valencia),

•Belgium(Brussels-Lille),•TheNetherlands(Amsterdam-Brussels),•TheUnitedKingdom(London-Dover),•Russia(Moscow-St.Petersburg),•Turkey(Ankara-Istanbul),•Korea(Seoul-Busan),•Taiwan(Taipei-Kaohsiung),•USA(North-EastCorridor(Washington-NewYork-Boston)),•China(Beijing-Shanghai,Ningbo-Xiamen,Zhengzhou-Xian,Nanjing-Wuhan-Guangzhou-Shenzhen,Beijing-Zhengzhou-Wuhan-Guangzhou).

Table2.1illustratestotalkilometersofhigh-speedraillinesaroundtheworld(inoperation(2012),underconstruction(2012)andplanned),withthe

correspondingmaximumspeedineachcase.Atotalof20,819kilometersofhigh-speedlineswereinoperationworldwidein2012(a2%oftotalrailwaylinesallovertheworld).

Table2.1.High-speedraillines(inoperation(2012),underconstruction(2012),

planned)invariouscountriesallovertheworld(compiledfromdataof(1))

ThoughmanyEuropeancountrieshaveplannedanumberofnewhigh-speedraillines,theeconomiccrisisinmostofthesecountriesmaydelayorevencancelanumberoftheseprojects,atleastintheforthcomingyears.ThusChinaisthecountrywherehigh-speedraillinesareincreasingmostrapidly.Indeed,althoughChinaisbuildinghighwaysrapidly,itwillbeimpossibletomaintainhighwaytrafficorprivatecarownershipatthelevelofcountrieslikePortugal.Thus,inordertosupportmobilityinChina,HSTmayappearastheonlycost-efficientandviablesolution,(8).

IntheUSA,anumberofroutes(Table2.2)havebeensuggestedascandidatesfornewhigh-speedlines.Ithasbeendifficult,however,todeviseatrustworthyfundingmodel.MostEuropeanandAsianhigh-speedlineshavebeenconstructedbypublicfunding.SuchamodelcannotworkintheUSA,whereabalanceandacompromiseshouldbetargetedamongtheprivatesector,theStatesandtheFederalGovernment.

2.1.3.Highspeedsforonlypassengerormixedtraffic

Twoapproachesofhighspeedscanbedistinguished,(45),(48):inthefirst,onlypassengertrainsrunonhigh-speedlines,withlowaxleloads,verysmalltolerancesoftrackdefectsandlargegradients(upto35‰).ThisapproachwasimplementedintheParis-Lyonsandotherlinesandpresupposesahighrailpassengertraffictomaketheconstructionandoperationofthenewlinecost-efficient,inthesecond,thenewhigh-speedlinesarerunbybothpassengerandfreighttrains,thecoexistenceofwhichentailshighermaintenancecostsandrequireslowervaluesforthelongitudinalgradient.Mosthigh-speedlinesarecurrentlydesignedformixedtraffic(bothpassengerandfreighttrains).

Inanycase,foraspecificHSTsystem,topspeedrepresentsacompromisebetweentheadditionalcapitalinvestmentrequiredtoachieveatopspeedandthehigheroperatingcostandthetraveltimesavingsresulting.

HSTruntodaywithamaximumspeedof320km/h,whichmaybeincreasedupto350km/huntil2020.However,theBeijing-Shanghaihigh-speedlinewasdesignedforamaximumspeedof380km/h,butduetohighoperatingcostsmaximumspeedwasreducedto300km/h.Furtherincreaseofspeedbeyond350÷380km/h,however,seemsdifficulttoberealized,duetothefollowinginherentlimitationsoftherailtechnology,(44):–difficultyincollectingelectricpower,

–reducedadhesionbetweenwheelandrailathigherspeeds,causingwheelslip,–greatersizeandweightofonboardequipment.

Table2.2.SuggestedcorridorsintheUSAfornewhigh-speedraillines,(8),(38)

2.2.High-speedtrainsandtheirimpactontherailmarket

2.2.1.Highspeedsandpopulationconcentrations

Highspeedsrequirenewlinesormajorimprovementsonexistinglines.The

highconstructionandoperationcosts(seealsoTable5.1)cannotbejustified,unlessalargenumberofrailtripsarerealizeddaily.Afirstindexforthejustificationofanewhigh-speedlinemaybepopulationconcentrationsonbothendsoralongtheline(Figure2.2).Foranewhigh-speedlinetobeeconomicallyjustified,apopulationoftenmillionpeopleattheoneendandfourmillionpeopleattheothermaybeconsideredasaroughfirstcriterion.Otherwise,high-speedlinesmaybecomeanonprofitableactivity,(37),(39).

Figure2.2.Populationconcentrations(inthousands)alongmajorhigh-speedlinesaroundtheworld.Thegreaterareaofeachcityisconsidered

2.2.2Impactofhighspeedsonthereductionofrailtraveltimes

Thereductionoftraveltimeshasbeenaconstantgoalofrailways,ascanbeseeninTable2.3.OnlywithHST,however,wererailwaysabletoachieveon500÷1000kmroutestraveltimesequaltoorbetterthanairtransportandthuscompeteefficientlywithairplanes.

Indeed,HSTcapitalizeontheiradvantagetoreachcitycentersandthusmaketraveltimesfromthecenterofacitytothecenterofanotherfarshorterthanforautomobilesandeven,inmanycases,shorterthanforairplanes,(Table2.4).

HSTreducedrecentlytraveltimesintheMadrid-Barcelona(622km)routefrommorethan6hto2h30min,intheBerlin-Hamburg(286km)routefrom2h20minto1h30min,intheMilan-Rome(560km)routefrommorethan4hto3h,intheTaipei-Kaohsiung(345km)routefrom4hto1h30min,andintheBeijing-Shanghai(1,318km)routefromaround10hto4h48min.

Table2.3.Railtraveltimereductiononcertainhigh-speedroutes

Table2.4.Comparisonoftraveltimesfromthecenterofacitytothecenterofanotherforrailways,airplanesandautomobiles(caseoftheParis-Lyonsroute),(48)

Figure2.3illustratestraveltimesbeforeandaftertheoperationofHST.Ifwetrytocorrelatehigh-speedrailshareswithtraveltimes,alinear

correlationmaybeestablished,(Fig.2.4),witharatherhighcoefficientofdeterminationR2(R2=0.74),(seealsosection4.4.1).Thecorrelationislesssatisfactorybetweenrailshareandtraveleddistance(R2=0.65),(Fig.2.4).

Figure2.3.Traveltimesbeforeandaftertheintroductionofhigh-speedtrains

Figure2.4.Railshareinrelationtotraveltime(——line)anddistance(----)line

2.2.3.Highspeedsandnewrailtraffic

Anotherresultofhighspeedswastheincreaseoftraffic,eitherasdiverteddemandfromairandroadtransportorastotallynewdemand(generateddemand).Figures2.5and2.6illustratehigh-speedrailtrafficinthecountrieswithhigh-speedlines.AccuratedataaboutChinawerenotavailable,thoughhigh-speeddailyridershipwasreportedtobe349,000in2008,492,000in2009and796,000in2010.

Figure2.5.Evolutionofhigh-speedrailtrafficinEurope,(1),(2)

Figure2.6.Evolutionofhigh-speedrailtrafficinAsia,(1),(2)

Highspeeds,therefore,attractbacktotherailwayspartofthepassengertrafficlostinthepast,orgeneratenewtraffic.Forthispurpose,however,aspeedincreaseisnotenough:stationaccessibilityshouldalsobeimprovedthroughefficientbusormetrosystems.Inmanyinstances,theconnectionofrailway

stationsservingHSTtoairportscancontributetoanefficient(intermsoftimeandcost)air-railtrip,asexplainedpreviouslyinsection1.10.

However,thesuccessofHSTisnotonlyduetothereductionoftraveltimes,butalsotothefollowingcharacteristics:–frequencyofservice,–regular-intervaltimetables,–ahighlevelofcomfort,–apricingstructureadaptedtotheneedsofcustomers,–complementaritywithothermeansoftransport,–moreon-boardandstationservices.

Ahigh-speedrailsystemshouldbedesignedtoincorporatethewholerangeofserviceswhichthecustomerhascometoexpectwhentravelingonHST,includingbothpre-travelservices(information,ticketpurchasing,seatreservation,etc.)andpost-travelones(after-salesservices).

2.3.Technicalfeaturesofhigh-speedrailwaylines

2.3.1.Technicalcharacteristicsofhigh-speedlines

Table2.5illustratesthetechnicalcharacteristicsofsomehigh-speedraillines.Importantdifferencesregardinggradientsandelectrictractionsystemsareobserved.

2.3.2.Trackcharacteristicsforhighspeeds

HSToperationrequiresthatthetrackbebuiltandmaintainedtomuchmoredemandingspecificationsandclosertolerancesthanconventionalandlower-speedtracks.ContinuousweldedrailsoftypeUIC60,concretesleepers(monoblockortwin-block),andelasticfasteningshavebeenusedtoimproveridequality,stabilityandsafetyofthetrack.Indeed,HSThaveoutstandingsafetyrecords,duetoexclusiverights-of-way(insomecases),fencing,computerizedtraincontrol,andextremelygoodmaintenance.Insteadofballastedtrack,somecountries(JapanandGermany,amongothers)haveusedaslabtracksolutionforHST(seealsochapter17).

Table2.5.Technicalcharacteristicsofhigh-speedraillines,(43),(47),(48)

2.3.3.Rollingstockforhighspeeds

Rollingstockusedforhighspeedscompriseslightweight,streamlinedandelectricallypoweredlocomotiveshandlingpassengercoachesorsimplytrainsofself-propelledmultiple-unitcars.Theirlightweightminimizeshorsepowerandbrakingeffortrequirements,wheelwearandtrackdegradation.Tractionmotorsarenormallycarbody-mounted,ratherthanaxle-hung,toreduceunsprungmasses(i.e.massesbelowtheprimarysuspensionsystem,seealsosection7.11.2),(44).

2.3.4.Powersupplyathighspeeds

PowerissuppliedtoHSTfromwaysidesubstationsthroughoverheadcatenarywiresandiscollectedthroughpantographsmountedonthelocomotiveorpowervehicleroofs.Athighspeeds,thecatenarytensionmustbemaintainedataconstantvaluetominimizevariationsofsag.TheFrenchHSThasatwo-stagepantographinordertominimizepressure(uplift)andtomaintainexcellent

currentcollectioncharacteristicsathighspeeds.Themajorityofotherpantographsystemsusemuchmorerigidandmorecomplexcatenarieswithahighertension,resultinginlesssag,(seesection20.8).

2.4.TheChannelTunnelandhighspeedsbetweenLondonandParis

2.4.1.Technicaldescription

ThegovernmentsoftheUnitedKingdomandFrancedecidedin1986onapermanentrailwaylinkbetweenthetwocountries,toberealizedentirelybyprivatefinancing.ForthispurposetheEurotunnelConsortiumwascreatedwithresponsibilitiestoconstructtheTunnelandoperateitfor55years,whichwasextendedlaterto99years,(40).

Theprojectofatotallengthof50.5kmconsistsoftworailtunnels(oneperdirection)withaninternaldiameterof7.6mplusathirdtunnel(ofaninternaldiameterof4.8m),formaintenancepurposes,emergencyincidents,etc.Theprincipaltunnelsareconnectedtotheauxiliaryoneat375mintervals.Theraillevelissituated25÷40mbelowtheseabedlevel.

Theentireconstructioncostwasinitiallyunderestimatedat4.2billion€,changedmanytimes,wasfinalizedat7.4billion€andisallocatedasfollows:50%forthetunnelconstruction,10%fortherollingstock,40%fortracks,signaling,electrification,etc.

2.4.2.Traveltimes

FulloperationthroughtheChannelTunnelbeganintheautumnof1994.Threetypesofservicesareprovided:•high-speedtrains,(named“Eurostar”),witharunningspeedinthetunnelof160km/h,joiningLondontoParisin2013in2h15minandLondontoBrusselsin2h01min.Eurostartrainshaveacapacityof794passengers(584insecondclassand210infirstclass).In2010Eurostarhadashareof79%intheair+railtransportmarketbetweenLondonandParisandashareof65%betweenLondonandBrussels,withapunctualityapproaching94%,

•conventionaltrains,nighttrains,freighttrains,withausualspeedof100÷120km/hintheChannelTunnel,

•shuttlepassengertrains,(named“LeShuttle”),transportingcars,trucks(ofa

maximumweightof44tons)andbuses.Passengersremainintheirseatsandmaximumspeedinthetunnelis140km/h.Theshuttletrainsrequireextensiveterminalfacilitiesateachend,around1.3millionm2intheBritishsideand7millionm2intheFrenchside,thesizeofamajorinternationalairportlikeHeathrow,(43).

MoretechnicaldetailsabouttheChannelTunnelaregivenintherelevantchapters(soilmechanicsinsection9.2.5,etc.).

2.4.3.Methodoffinancingandforecastsofdemand

Assaidpreviously,notapublicpenny(=0.012€)hasbeengivenforEurotunnel,whichwastotallyfinancedbytheprivatesector.ForecastsforEurostarestimateddemandfortheyear1995at11.5millionpassengers,whereastherealnumberwasonly2.92millionpassengers,andfortheyear2003at18.9millionpassengersagainstonly6.31millionpassengerstraveledthatyearand9.68millionpassengerstraveledin2011.Demandofshuttlepassengertrainswas4.2millionpassengersin1995,increasedto12.2millionpassengersin1998andthendroppedto7.8millionpassengersin2011.TotalfreighttransportedthroughtheChannelTunnelwas6.5tonsin1995and17.7tonsin2011.Figure2.7illustratesevolutionofthevariouscategoriesoftrafficthroughtheChannelTunnel.

Overestimationofdemandandunderestimationofcostsledtoarealfinancialdisaster,whichisreflectedinthevalueofEurotunnelshare(issuedat£3.50in1987,increasedto£11.00in1989)inthestockmarkets,whichdroppeddown4timeslowerinlate1994comparedtoitsinitialvalue.

Fig.2.7.EvolutionofthevariouscategoriesoftrafficthroughtheChannelTunnel(1),(2)

2.4.4.Operation,safetyandmaintenance

Theultimatecapacityofthesystemcanreach30trainmovementsperhourineachdirection.12%ofthepersonnelofEurotunnel(3,465peoplein2012)areinchargeofmaintenance.

TheTunnelhasahugecoolingsystemandasignalingsystemthatincorporatesfullautomatictrainprotection.ThesystemprovedratherefficientinthefireofNovember1996ononeofthefreightshuttles,withoutanyvictims,butwithseriousdamageswhichresultedinclosingtheaffectedtunnelfor7monthsforrepairs.

2.5.Tiltingtrains

HSTrequirenewlayoutsandnewtracksandareoftenanexpensivesolution,whichisfeasibleonlyforveryhighpopulationconcentrations(asillustratedpreviouslyinFigure2.2)ateachendoralongtheline.However,theusualreasonfortherestrictionofspeedisthesmallradiusofcurvature.

Therailwayindustrydevisedasolutionwhichpermitsanincreaseofspeedincurveswithoutthenecessityofimprovingthelayout(i.e.,toincreasetheradiusofcurvature).Theextremelyinterestingsolutioniscalledtiltingtrain,duetothefactthatthevehiclebodytiltswhennegotiatingacurveandthusgivesan

additionalsuperelevation.Tiltingtrainsarenot,strictlyspeaking,HSTbuthavesucceededreductionof

traveltimesupto33%comparedtoconventionaltrains.However,medianreductionoftraveltimesbytiltingtrainsrangearound12÷20%.TiltingtrainsareinuseinItaly,Spain,theUnitedKingdom,Sweden,Finland,theUSAandelsewhere.Thetiltingtechnologyisanalyzedindetailinsection19.9.

2.6.Aerotrain

Theaerotraintechnologyisbasedonguidedtransport(likeconventionalrailways),butavoidsanycontactbetweenthemovingvehicleandthebearingsubstructureonwhichtransportistakingplace,whereasrailwaysrelyonthemetal(wheel)tometal(rail)contact.Theaerotrainisavehiclerunningonaconcretebearingsubstructureintheshapeofaninverted“T”,(Fig.2.8).

Fig.2.8.Theaerotrainprinciple

Propulsionisachievedwithoutanywheelsystem,byacompressedaircushionblownbetweenthevehicleandthebearingsubstructure.Thus,theaerotrainreplacestheadhesionforces,necessarytopropelconventionaltrains,bycompressedairlayers,(48).

Thistechnologywasdevelopedinthe1960sinFranceandin1974achievedthespeedof430km/h.Eventhoughtherewerevariousplansforaerotrainconstruction(e.g.Paris-Orleans,where18kmofbearingsubstructurehadevenbeenbuilt,Brussels-Luxembourg,etc.),theywereabandonedinthe1970sforvariousreasons,themainonesbeing,(48):thenewtechniquewasnotcompatiblewithconventionalrailways,constructionprovedtobemuchmoreexpensivethananewconventionalrailwayline(withouttheadditionalcostbeingoffsetbythemuchlowermaintenancecostoftheaerotraincomparedwithconventionalrailways),

energyconsumption(duetotheairturbineusedforaerotrainpropulsion)wasmuchhigherthanforconventionaltrains,thecarryingcapacityoftheaerotrainwaslow(64÷96passengersintheprototype,butupto160passengersintwo-vehicleaerotrains).

Secondaryreasons,suchaspassengersafetyconsiderations(possiblefireinthevehiclewhichrides5maboveground),noiseandquestionableoverallaestheticshavecontributedtotheabandonmentoftheproject.

2.7.Magneticlevitation

2.7.1.Technicaldescription

Inmagneticlevitationsystems,contactbetweenthebearingsubstructureandthevehicleisavoided,propulsionbeingensuredbymagneticphenomena,(Fig.2.9).Thebearingsubstructureisaconcreteslabintheshapeofaninverted“T”(orofa“U”).Suitablylocatedmagnetsandcoilsgeneratetheforcesrequiredforlevitation,propulsion,andguidance.However,asuper-conductingmagnet,fulfillingtheabovethreerequirementshasbeenconstructed.Themaglevtechnologywasdevelopedinthe1970sinGermanyandJapan,whereduringthecourseoftestingaspeedof517km/hwasattainedin1979andof581km/hin2003,(44),(46).

Fig.2.9.Themagneticlevitationprinciple

Manyofthehandicapsoftheaerotraininventionarestillvalidforthemaglevaswell,suchasthegreaterdifficultyinvolvedinpenetratingcitycenters,incontrasttoconventionalrailways.However,pressurefromtherailindustryandpoliticalgoalshaddelayedapplicationsofthemaglevinvention,(41).

Twodifferentmaglevtechnologieshavebeendeveloped:Attractionor

electromagneticsuspensiontechnology,developedbyGermany,andrepulsionorelectrodynamicsuspensiontechnology,developedbyJapan.ThebasicfeaturesofthetwomaglevtechnologiesarelistedinTable2.6,(44),(46).

Table2.6.Basicmaglevtechnologyfeatures,(44)

2.7.2.Comparisonofmagneticlevitationwithconventionalrailways

Advantageousfeaturesofthemaglevtechnologyare,(41),(46):–itcanoperateathighspeedsintherangeof400÷500km/h,–thereisnolossoftractionathighspeeds,sincethereisnovehicle-trackcontact,

–thereisnowheel-railfriction.Theonlyresistancetobeovercomeisaerodynamicdrag,

–thereisnohindrancefromrail,iceorsnow.–itisveryquietbecauseoffew,ifany,rotaryorslidingpartsinmaglevvehicles,

–thereisnopossibilitytoderailfromtheguideway,sincethevehiclesareintimatelycoupledtotheguideway,

–therearelowmaintenancecostsbothforthevehicleandthetrack,becauseof

theabsenceofmechanicalcontact,–itcannegotiatesharpcurvesandsteepergrades,sincewheelfrictionisnotafactorinpropulsion.

Thusmaglevsystemscanclimbsteepgradesupto100‰andnegotiatecurveradiiof2,250mataspeedof300km/h.Ontheotherhand,themaglevsuseapproximately30%lessenergythanaconventionalrailwaytraintravelingatthesamespeed.

Themagneticfieldinfluenceisslight,(Fig.2.10),andanynegativeeffectonpassengerswithpace-makersiscompletelyruledout.

Lastly,itshouldbenoticedthatwithnorollingnoise,maglevsystemsaremuchquieterthanconventionalrailwaysystems(seealsochapter22),(42).

Fig.2.10.Themagneticfieldofamaglevsystemincomparisontootherexposuresofthehumanbody,(41),(42)

2.7.3.Applicationsofmagneticlevitation

Manyprojectsformaglevapplicationshavebeenplannedinthepast,buttherewereonlythreemaglevsystemsinoperationin2013:–themaglevsystemconnectingtheairportofShangaiwiththecenterofthecity(adistanceof30.5km)in7minutes,amaximumspeedof431km/handapunctualityof99.97%.Theprojecthadacostof1.2billionUS$andthefirstyearoffulloperation(2004)wasarealfinancialdisasterwithaloadfactorofonly17%andatrafficfarawayfromtheinitialforecastof8millionpassengersperyear(whichis22%oftrafficoftheShanghaiairport),principallyduetothenon-accessibilityofitsterminals.

–ThemaglevsystemnearthecityofNagoyainJapan,whichwasinauguratedin2005.Itsmaximumspeedisonly100km/h,sincethesystemwasdesignedasanalternativetometrosystems.Maximumcarryingcapacityisonly4,000passengersperhourandperdirection,theminimumradiusofcurvatureis

75mandtheoverallconstructioncostperkm(rollingstockincluded)was100millionUS$.

–ThemaglevsysteminDaejon,SouthKorea,servingtheneighboringairport.

*TGV:TrainàGrandeVitesse

3PolicyandLegislation

3.1.Thecompetitiveinternationalenvironmentandtheevolutionoftheorganizationofrailways

Theorganizationofrailwaysbeganinthelate19thandearly20thcenturiesintheformofsmallprivateenterprises.Thestrategicimportanceoftherailwaysfortheeconomyandthesecurityofvariouscountries,combinedwiththedeficitswhichhadalreadybeguntoappear,ledmostgovernments,between1935and1960,tonationalizetheirrailways.Therefore,mostrailwaysbecamepartofthestateadministrationorwereunderstatecontrol(1960s÷1980speriod).

Changesinthetransportmarketduringthe1980sand1990s(mainlythegradualliberalizationandderegulationoftransportactivitiesfromtheregulatingframeworkunderwhichtheyhadbeenoperatingforfourdecadesormore)compelledrailwaystoshowmoreflexibilityintheorganizationoftheirservices,reducecosts,adapttonewtechnologies,exploittheircomparativeadvantages,andmodernize,inordertobecomecompetitiveinthetransportmarket.Somecountries,likeJapan,GreatBritain,Swedenetc.,havealreadyprivatizedtheirrailwayoperators.Inthetransportmarket,neithertechnologynorinnovationwillhaveareasontoexisttheseconddecadeofthe21stcentury,unlesstheyarefinanciallyefficientandcompetitive,comparedtoservicesofferedbyothertransportmodes(roadvehicles,airplanes),(12),(15),(36).

AnimportantsteptowardstheliberalizationofrailwayactivitiesinEuropewastheseparationofinfrastructurefromoperation,puttinganendtoamonolithicorganizationoftherailways.

3.2.Thedualnatureofrailways:businessandtechnology

3.2.1.Weaknessesinheritedtorailways

Inthecompetitiveenvironmentofthetransportmarket,railwaysshouldsearchfortheircomparativeadvantages,whichtheyshoulddevelopwiththehelpofthe

necessarytechnologicalmodernization.Ontheotherhand,theyshouldoperateasenterprisesgovernedbythesamerulesofcompetitionappliedtootherbusinesses,relinquishingtheumbrellaofstateprotectionismshelteringthemfordecades.

Railways,however,inheritserioushandicapsasaresultofdecadesofstateprotectionism,suchas,(63),(68),(69):administrationandorganizationinflexibility.Fordecades,railwaymanagementdealtonlywithcurrentaffairsandwasinvolvedprincipallyintechnicalmatters.Importantissuesweredecidedbythesupervisingministry,oftenbasedonpoliticalcriteria,accumulationofpersonnelinroutinetasksandstaffshortagesforadministration,organizationandtechnologicalupgradingpositions,highcosts,oftentheresultofobsoleteoperatingmethodsandstaffover-crowding,rollingstockoftendifficulttooperate,offeringservicesofalevelwhichdoesnotmeettransportrequirementsinmanycases,maintenanceexpensesofrailwayinfrastructureundertakenbytherailways,ascontrastedtoroadandaircarrierswhichcontributeonlyasmallpartofthemaintenancecostsofroadnetworkandairportsrespectively.Separationofinfrastructurefromoperationwasanimportantsteptoovercomethissituation,obsoleteinfrastructure(whichwasoverdimensionedinmanycases),oftenasaresultoftheabsenceofseriousinvestmentformanydecades,obligationtooperatelineswithalowtrafficwithoutsufficientcompensation,which,hadthelinebeenoperatingbyprivateenterprisecriteria,wouldnothavesustaineditsoperation.

3.2.2.Comparativeadvantagesofrailways

Theaforementionedcompendiumofdisadvantagesrisksgivingtheimpressionthatrailwayshavenothingbutproblems(whichtoalargeextentareofthemakingofothers).However,railwayscontributetothedevelopmentofbothtransportandtheeconomy,sincethey,(15):•provideanintegratedsystemofservicesforbothpassengerandfreighttransport,withprogrammedschedulesregardlessofday,seasonandweatherconditions,afactresultinginnetworkeconomies,

•pollutetheenvironmentminimallyincontrasttoothertransportmeans,•contributedecisivelytorelievecongestioninpeaktravelperiodsincentralthoroughfares,becauseoftheirhugetransportcapacity,(seesection1.9.2),

•consumemuchlessenergyforthesametraffic,comparedtoanyothertransportmode,

•providereducedfaresforlargesegmentsofthesociety,particularlyforsocialreasons(e.g.students,theelderly,etc.)whocanthustravelmoreeasily.

3.2.3.Strategyandrestructuringmeasures

ThetransportsectorinEuropeandworldwideispresentlyorientedtoagradualliberalizationandderegulation*,withemphasisoncompetitionbetweenthevarioustransportmodes.Thegovernment-ownersoftherailwaysareundertheobligationtoensurearealautonomyfortherailways,tograduallyreducesubsidiestorailundertakings(usedtocoverdeficits),toinstitutearegimeoftransparencyinrailoperationsandtocreateaframeworkinwhichotherrailoperatorscanusetherailwayinfrastructureandentertherailtransportmarket.Withinsuchaframework,therailwaysshouldaimat,(12),(15),(36),(57),(69):–marketorientedactivitiesandtheeventualabandonmentofunprofitableservices,

–greaterflexibilityintheorganizationanddevelopmentofoperationalcriteriaforthevariousinitiatives,e.g.investment,

–personnelallocationonthebasisoftherequirementsoftheparticulartransportationtaskandstaffingofthevariousdepartmentsbyspecializedpersonnel.Itisnottoexclude,particularlyformanagementandspecializedtasks,theuseofhigh-qualityspecialistsfromothersectors,

–tryingtoreducedrasticallycostsinordertomakerailservicesmorecompetitiveinthetransportmarket.Thereductionofcostsmaycomefromtheapplicationofinformaticstechnologies,internetandothernewtechnologiesinadditiontotherationalizationandinevitablereductionofthecurrentpersonnellevels,whichislinkedtothedownsizingoftheundertaking,

–systematicmaintenanceandrenovationoftherollingstockandinfrastructure,enablingtherailwaystomeettherequirementsoftheirclients,

–infrastructuremodernizationwithimportantinvestment(forthemostpartthiscanbecoveredbythestate,theEU,theWorldBankandinsomecasesbytheprivatesector).Itshouldbestressedherethatmodernizationdoesnotrefertoanyparticularproject,buttothosethatwillenablerailwaystocoexistcompetitivelywithothertransportmeans.Forthemoreattractiveprojects,financingcancomefromtheprivatesectortoo,aswasthecaseoftheChannelTunnelProject,

–cleardefinitionofpublicserviceobligationsinthepassengersector,being

understoodasthosewhich,iftheonlyconsiderationoftherailwayswerebusinessprofit,wouldnothavebeenundertakentothesameextentordegree(e.g.operationoflineswithsmalltraffic).Theauthorityenforcingamandatorypublicservice(e.g.theMinistryofEducationforreducedstudentfares)shouldrefundlostincometotherailwayoperator,

–adequatecompensationoftherailwaysfornotpollutingtheenvironmentandnotcausingtrafficcongestion.Aquantitativeandfinancialevaluationoftheeffectsofthevarioustransportmodesontheenvironmentisalreadyavailable,(seesection5.7).Theprevailingviewistosubsidizerailwayswithanamountcorrespondingtothatwhichwouldhavetobeexpendedtocombatthepollutionandtrafficcongestion,whichwouldhavebeencaused,hadtheoperationoftherailwaybeendiscontinued,

–gradualreductionofdeficits.TheratioRevenues/Expenses,whichrepresentstheabilityofacompanytosurviveornotwithoutanysubsidiesisgiveninTable3.1forEuropeanrailways.InthesameTable,personnelcostsasapercentageoftotaloperatingcostsareprovided.GreatdifferencesfromoneEuropeancountrytoanothercanbemonitored.However,asdeficitsofrailwaysarecoveredbythestatebudget,thatisbythecitizens(whooftenarenotusersofrailways),astrongpressuretotherailwaysisexertedandwillcontinueforthereductionofdeficits,

–commercialandtariffpolicieswhichincreaserevenues,assurehighdegreesofloadfactorandrespondtorequirementsofclientsandthesociety,

–fulfillingfinancial,commercialandtechnologicaltargets,whichshouldbeclearlydefined.Factorsthatcanmeasuretheglobalresultofarailwayundertakingcanbethedegreeofadaptabilityandtheoperatingcosts,(Fig.3.1,page48),whichpresenthugedifferencesandverycontrastingsituationsamongthevariousEuropeancountries.

3.2.4.Railwaysandtransportrequirements

Anytransportactivityisnotanendinitself,butexistsinordertofulfillspecificneedsoftransportofpersonsandgoods.Railwaysshouldtrytooffermoreefficientandcompetitiveservicesandmusttakeintoaccountthefollowing,(15),(57),(69):

Table3.1.TheRevenue/ExpensesratioforInfrastructureManagersandRailwayOperatorsinvariousEuropeancountries(in2004),(57)

Fig.3.1.Adaptabilityandrailwayoperatingcostsforsomecountries,(61)

–theevolutioninthetransportmarket,resultingfromglobalizationoftheeconomy,liberalizationandincreasingderegulation,

–competitionandtheneedforreductionofcosts,–theobligationforharmonization,knownasinteroperability,ofthevariousrailwaytechnologies(e.g.trackgauge,electrificationandsignalingsystems),topermitaglobalrailwayservice,

–theneedforalong-termoperationalprofitability,–theneedforadownsizingpolicyandamarketorientedstrategyfocusingonprofitablesegments.

Survivalintheevolvingandhighlycompetitiveinternationalenvironmentdemandsahigherqualityofservice,withefficient,accessibleandcompetitiverailtransportsystems.Thesesystemsmustfulfilleconomicandsocialexpectations,whilstensuringobjectivesofwiderenvironmentalprotection,efficiencyofresourcesandsafety.Moreover,raildevelopmentshouldallowformaximumsynergywithothertransportmodes,thusrespondingtomodern,door-to-doorrequirementsforseamlesstransportandmobility.

3.3.Globalizationandliberalizationoftherailmarket

Theseconddecadeofthe21stcenturyischaracterizedprincipallybytwofacts:•anincreasingglobalization(ofeconomicandcommercialactivities),whichcanbedescribedasaprocedureofopeningnationalmarketstoproductsandservicesandreducingstatesubsidiesandcosts.

•theeffectsontherailwaysoftheinternationalfinancialcrisisandthedebtcrisisinEuropewhichresultinlessinvestmentforrailinfrastructure,reduction(orevenabolition)ofstatesubsidiesforbothinfrastructureandoperationoftherailwaysandlessdisposableincomeofcitizensfortransportconsumption.

Globalizationrequiresacompetitiveenvironmentandliberalizationofthetransportmarketandmoreparticularlyoftherailsector,whichisunderstoodasthewithdrawalofanyobstaclesconcerning:entranceofnewoperatorsintherailmarket,commercialandtariffpolicyoftherailwayundertakings,management,strategy,investment,etc.

Railliberalizationgeneratesbothopportunitiesandthreatsforrailways,(15):–intra-modalcompetition(i.e.,fromotherrailoperators)willpressforreducedrailtariffsandincreasedqualityofrailservices,

–statesubsidieswillbeabolishedorreducedandinanycasethecontinuationofoperationofarailactivitycausingdeficitsshouldbeappropriatelyjustified;thusrailwayswillbepressedtocurtailcostswithasaninevitableeffectthelossofjobsinaneraofrisingunemployment,

–newinvestmentswillintroducenewtechnologies,whichwillincreasequalityofservices,createnewproducts(concerningparticularlyinternationalrailservices,combinedtransport,highspeeds,etc.),

–amorecustomerorientedcommercialandtariffpolicywillpermitrailwaystogainsegmentsofthemarket,suchasbusinesstravel,transportofgroups,transportofbulkordangerousloads,etc.

However,eveninaliberalizedrailmarket,theroleofthestateremainscriticalandshouldassure,(58):•highstandardsofsafety,•acertainlevelofqualityofservices,•thatonlynewoperatorswithasufficientfinancialcapacityandtechnicalperformancescanentertherailmarket,

•faircompetitionforinter-modal(withothertransportmodes)andintra-modal(withotherrailoperators)competition,

•transparencyandaccountabilityintheuseofpublicfunds,•astableeconomicenvironmentforlong-terminvestmentsandtechnologicalinnovations,

•preventionofpricingabuses,•anappropriateenvironmentforthereductionofcosts,whileavoidingsocialunrest,

•furtherdevelopmentofinternationalrailservices,whichpresumesthesimplificationofcustomsproceduresandefficientcooperationbetweeninfrastructuremanagersandrailoperators,

•aneworganizationthatavoidsunnecessaryfragmentationandlimitstherisksandcostsconcerningbothfinancesandsafetyinmanagingtheinterfacebetweentrainoperationsandinfrastructure,withclearidentificationoftheresponsibilitiesofeachpart,

•writingoff(totallyorpartially)pastdebts.

However,liberalizationshouldbeclearlydistinguishedfromprivatization,i.e.,thepropertyregimeofanundertaking.Itispossibletohaveaprivatizedrailoperatorwithmonopolisticrights(thecaseofmanyrailoperatorsintheUnitedKingdom)orastate-ownedrailoperatorinacompetitivecontext(thecaseofmanyofnationalrailways),(55),(66).

3.4.Separationofinfrastructurefromoperationandthenewchallengesforrailways

3.4.1.Separationasanincentiveforcompetition

Therailwayofthepastwasinmostcasesanaturalmonopolywithaspecificstatusforitsstaff.Initsmonolithicorganizationtherailwaysystemhadtwolevelsofcontactwiththeexternalenvironment:thestate-ownerandthepassengers,whowerenotusuallyconsideredasclients.

Insection3.2.3wedescribedsomemeasuresthatrailwaysshouldundertakeontheirinitiative.Manyrailwayshavebeenreluctanttorestructure,evenwhentheyhavebeenpressedtotakesomemeasures(suchastheclosureoflinesorreductionsofpersonnel).

Therefore,thequestioniswhetheritispossibletoreversethedeclineoftherailwaysbymeansofreformsbasedoncompetition,whichcanbecomethecatalystforradicalchangesintheoligopolistictransportsector,(65).

Theanswerliesontheideasofcontestability:thethreatthatapotentialcompetitorcanenterthemarketisacriticalandsufficientmotivationfortheexistingoperatortobehaveasifcompetitionexisted,(60).

Thetendencyoftheperiod1985÷2013torestrictmonopolisticactivitiesand

introducecompetitioninallsectorsoftransportwillbecontinuedandstrengthened,asthisisencouragedbytheinternationaleconomicenvironment.Airtransportisfullyliberalizedinmanycountriesoftheworldandnationalcarriers,whoenjoyedmonopolyandstateprotectionforyearsinbothinternationalanddomesticroutes,arestrugglinginaverycompetitiveenvironmentwithprivatecarriers(oftenlow-cost)whoenteredthemarket.Thequestionarises,whetherthismodelshouldalsoapplytotherailways,underwhatconditionsandfollowingwhichrates.

Ithasbeenarguedthattherecanhardlybeanycompetitionifrailwayskeeptheiroldorganization,withonestate-ownedcompanyinchargeofbothinfrastructureandoperation.Thus,theseparationofoperationfrominfrastructureappearedasafirststeptointroducecompetitionwithintherailwaymarket.Infrastructurewillbetheresponsibilityofanauthoritytotallyseparatedfromoperationandeveryrailwayoperatorwillpaychargesforusingatrack,inrelationtothetimeofthejourney,thedistancetraveled,thekindofrailwayoperation,etc.Chargesshouldnothaveanydiscriminationagainstnewentrants,(58).

However,thereisacounter-argumentwhetherthisseparationisaprerequisiteforcompetition.IntheUSAandelsewhere,railoperatorsowntheirinfrastructure,whereasanotheroperatorcanrunonaninfrastructurethatitdoesnotownbypayingappropriatecharges.

3.4.2.Competitionandnewchallengesforrailways

Inthisneworganizationoftherailways,manyfundamentalchallengesarearising,(15),(20),(51),(Fig.3.2):–Culture.Isthedifferencebetweenbeingaservice-renderingoperatorandanengineeringcompanyunderstood?

–Technology.Dosystemsfittonewobjectivesandrequirements?–Humanresources.Doemployeeshavetherightskillswithintheneworganization?

–Competition.Willtherebemanyandcompetingoperatorsontheinfrastructureandwhatwilltheimpactbe?Willrailoperatorsbepartnersorclientsofinfrastructure?

–Investment.Wherewillnewinvestmentcomefrom?IsaPrivate-Public-Partnership(PPP)feasible?

–Debt.Howwilltheaccumulateddebtbereimbursed?Mostlyfromthestate(caseofGermany),partlyfromthenewentrants(caseofJapan),andhow?

–Organizationalresponsibility.Asmultipleoperatorsrunonthesameinfrastructure,thiswillnecessitateastrongindependentinfrastructureentity,whichwillberesponsibleforpathallocation,trafficmanagement,etc.

–Roleofthestate.Inaliberalizedrailmarket,thestateshouldassumetheroleofRegulator.

–Reasonforexistence.Israilwaytransporteithertechnicallynecessaryormoreefficienttoassureafurtherincreaseinmobilityofpersonsandgoods?Whatistheaddedvalueofrailwaysinmoderneconomies?

Fig.3.2.Newchallengesforrailways(15),(20)

3.4.3.Variousformsofseparation

However,asstatedpreviously,acounter-argumentagainstseparationandforkeepingthestatusquooftheintegratedorganizationoftherailwaysisthatinsomepartsoftheworld(USA,Canadaforfreight,Japanforpassengers),arailwaycanbetheownerofinfrastructureandthisfactbyitselfdoesnotprohibitotheroperatorstorunitstrackbypayingappropriatecharges.

Thus,competitioncanexistwithoutseparation.Butseparationcanbethecatalysttointroducecompetitionortofacilitatetheentranceofmanyrailoperators.

Inrelationtothedegreeofseparationwecanobservevariousformsofseparation:–fullseparation(e.g.Sweden,UnitedKingdom,etc.).Allrailoperatorsareseparatedfromtheinfrastructureprovider,

–noseparationbutintra-modalcompetition(e.g.USA,Japan).Theinfrastructuremanagercontrolsandprovidesthedominantrailoperations,butotherminorrailoperatorscanrunonitsinfrastructurebypayingappropriatecharges,

–noseparationandnocompetition(e.g.China,India,etc.).Thereisonlyonefullyintegratedrailwaycompany,thatisoneinfrastructureproviderwhichisalsotheoperator.

Therearemanytypesofseparation(seealsosection3.7below):accounting.Railwayactivityisintegrated,onlyaccountsofinfrastructureareseparatedfromthoseofoperation,institutional.Infrastructureandoperationaretotallyindependentcompanies,bothfinanciallyandlegally,inaholdingstructure.Theformerintegratedcompanyissplitintwoormorecompanies,whicharemergedintoaholdingsystemwithacommonboardandchairman.

Amajorconcerninthetransitionfromthefullyintegratedrailwaytothevariousseparatedformsissafety.Therailwaysystemiscomplexandsafetransportisbasedonasynergyofitsvariouscomponents,whichshouldcontinue(andevenstrengthen)afterseparation.Anotherissueistransactioncostsandappropriatemanagementafterseparation,(seechapter6).

Separationmayservemanyobjectives,(58),(65):•clarifyrolesofgovernmentandthedegreeofitsinvolvementintherailwayactivity,

•encourageastrongerparticipationoftheprivatesector,•promotecompetition,intra-modal(withotherrailoperators)butalsointer-modal(inthemarket,withothertransportmodes),

•focusbusinessonpartsofrailwayactivity(e.g.freight),•establishcleartermsforrailinfrastructureprovision,•reducepublicsubsidiestotherailsector,•affordmorecustomer-orientedrailservices.

3.5.Adefinitionofrailwayinfrastructure

AdefinitionofrailwayinfrastructureisgivenbyEuropeanCommunityRegulation2598/1970andcomprisesroutes,tracksandfixedinstallationsnecessaryforthesafecirculationoftrains.

Railwayinfrastructureconsistsofthefollowingitems,(70):–Groundareaandthelineofroute.Itcomprisesthesubgradeitself,(seechapter9),includinginparticularembankments,cuttings,geotextiles,drainagechannelsandtrenches,masonrytrenches,culverts,liningwalls,plantingforprotectingsideslopes,etc.

–Thetrackandtrackbed,(seesection7.2,Fig.7.1),whichconsistoftherails,sleepers,fastenings,ballastandsubballast.

–Switchesandcrossings.–Engineeringstructures:bridges,culvertsandotheroverpasses,tunnels,coveredcuttingsandotherunderpasses,retainingwalls,etc.

–Levelcrossings,includingappliancestoensurethesafetyofroadtraffic.–Passengersandgoodsplatformsandaccessways.–Safety,signalingandtelecommunicationsinstallationswhichincludefixedsignals,trackcircuits,(seesection21.3.2),traincontrolequipment,signalcablesorwires,signalboxesandcontrolsystemsand(forhigh-speedlines)cabsignalingsystems.

–Electricitypowersupply,whichincludescatenariesandsupportsorthirdrail,substationsandpowersupplycablesandcontrolequipment.

–Lightinginstallationsfortrafficandsafetypurposes.–Buildingsusedbytheinfrastructuredepartmentandwithoutanyconnectionwithtransportactivities.

Stations,marshallingyardsandwarehousesmaybeownedeitherbytheinfrastructuremanagerorthetrainoperator.

3.6EuropeanUnionraillegislation

EuropeanUnionlegislationaimsto:introducecompetitionintherailmarket,rationalizeandreducepublicsubsidies,reducecostsandtransformrailwaystocustomerorientedbusinesses,achieveinteroperability,strengthensafety,boosthighspeedsandtakeadvantageoftheenvironmentalfriendlyperformanceoftherailways(12).

Keygoalsby2050oftheEUstrategyconcerningtransport,asdescribedintheso-calledWhitePaper,include,(12):

•a50%shiftofmedium-distanceofintercitypassengerandfreightjourneysfromroadtorailandwaterbornetransport,

•nomoreconventionally-fuelledcarsincities,•atleasta40%cutinemissionsofrailtransport,•a60%cutintransportemissions.

ThevarioussuccessivestepsintheEUraillegislationareoftenreferredtoasthefiverailwaypackages,(51),(56),(58):–railwaypackagezero(Directive440/1991),–firstrailwaypackage(Directives12,13,14/2001),aimingtoopentherailwaymarket,

–secondrailwaypackage(Directives49,50,51/2004),aimingtocreatealegallyandtechnicallyEuropeanrailwayarea,

–thirdrailwaypackage(Directives58,59,137/2007),aimingtoopenupinternationalrailpassengerservices,

–fourthrailwaypackage(underfinaldiscussioninspring2013),aimingtoliberalizedomesticrailpassengermarkets,torequirefullseparationofinfrastructurefromoperationandtostrengthenregulationonsafetyandinteroperabilityissues.

TheEuropeanUnionlegislationcanbesummarizedasfollows,(50),(51),(56),(58):Separate(atleastattheaccountinglevel)infrastructurefromoperation,(Directives440/1991,12/2001,14/2004,51/2004).Furthermore,separateattheaccountingleveltheactivitiesofpassengerandfreighttransport,andavoidanycrosssubsidiesamongthem,(Directive13/2001).Determinetheminimumconditions(aboutsafety,finances,etc.)tobemet,forarailoperatortoruninfrastructure(Directive18/95).Iftheseconditionsaremet,therailoperatorcanapplyforaLicense,validwithinallEUcountries.TheLicensesissuingBodyshouldbeindependentfromtherailwayoperators,(Directive13/2001).However,inordertooperateinaspecificcountry,theoperatormustalsopossessaSafetyCertificate,validonlyinthisspecificcountry,(Directive14/2001).Providemethodologyofpathallocationandcalculationofinfrastructurecharges(Directives19/1995,14/2001,58/2007).Infrastructurechargesshouldtakeintoaccountthenatureofservice,thetimeofitssupply,themarketsituation,andthequalityofrailwayinfrastructure,andshouldpreventcongestion.Comparableservicesshouldbesubjectedtothesamecharges.Sanctionsfordelayandbonusesforpunctualarrivalcanbeprovisioned.

Encourageagreaterparticipationoftheprivatesectorinrailwayactivities,suchasinfrastructurefunding(PPPpolicies,seesection6.3.5)andafurtherseparationoftheoperationintoseparatedunits(e.g.passenger,freight,commuter,etc.),(12).However,EuropeanUnionlegislationdoesnotimposeanyrulesonownershipoftransportundertakings(article222oftheTreatyofRome)leavingthepossibilitytothestatestoprivatizeornoteitherpartsortheentirerailwayundertaking,(55).Determinetheinfrastructuremanager’sdutiesthatshouldbefairandavoiddiscriminations,(Directive12/2001).IntroduceaRegulator,whowillsettledisputesintheplayingfieldandparticularlydecisionsoftheinfrastructuremanager,(Directive14/2001).Ensuretransparencyinfinances,withoutanypossibilityforstatesubsidiesforfreighttransport,aclearjustificationofstatesubsidiesforpassengertransport(throughpublicserviceobligations)andthepossibilityofsubsidiesfortheinfrastructuremanager,(Directive12/2001).Fulfillsafetyconditions;anyrailoperatorshouldpossessaSafetyCertificate,whichisissuedbyeachstate(andisvalidonlywithinthespecificstate)andexamineswhethertherollingstockischeckedandapprovedandifthepersonnel(particularlydrivers)areproperlytrained,(Directives14/2001,49/2004,59/2007,110/2008).Establishspecificrulesforinteroperabilityaimingtoassureexcellentcompatibilitybetweenthecharacteristicsoftheinfrastructureandthoseoftherollingstockandofoperation,inordertoincreaseperformancelevelsandsafety,toimprovequalityofservicesandtoreducecosts,(Directives50/2004and16/2001),(seealsosections1.13and21.9).OpenupnationalandinternationalrailfreightservicesontheEuropeanrailnetwork(sinceJanuary2007),(Directive51/2004).AimatthecreationofaEuropeanhigh-speednetworkwhichguaranteessafeanduninterruptedtravel,(Directives48/2004and50/2004):–ataspeedofatleast250km/honlinesspeciallybuiltforhighspeeds,whileenablingspeedsofover300km/htobereachedinappropriatecircumstances.

–ataspeedoftheorderof200km/honexistinglines,whichhavebeenorarespeciallyupgraded,

–atthehighestpossiblespeedonotherlines.Openupinternationalpassengertransport(sinceJanuary2010),(Directive58/2007).Takemeasuresinviewofafullliberalizationofallrailservices(including

cabotagerightsconcerningrailpassengertransport)inJanuary2018.Strengthensecurity(Directive49/2004)andallocatemoreresponsibilitiestotheEuropeanRailwayAgency,withdutiesonsecurity,interoperability,coordinationofpolicyandstrategies.Ensurebasicrightsofrailpassengersconcerninginsurance,ticketing,andpassengerswithreducedmobility(Regulation1371/2007).

3.7.SomerepresentativemodelsofseparationofinfrastructurefromoperationinEuropeanrailways

SomerepresentativeorganizationalmodelsofseparationofinfrastructurefromoperationinEuropearethefollowing,(58):

3.7.1.TheIntegratedmodel

ThismodelisappliedinLuxembourgandisbasedonthewilltomaintaintheintegrityoftherailwayactivity.Itmaybechoseninordertosatisfythewishesexpressedbyrailwaylaborunionsortoavoidpotentialsocialunrest.Themodelconsistsinthecreationofbusinessunitsforinfrastructureandoperation,withmanagementindependencebutwithoutlegalstatus,underacommonexecutiveboardandacommonchairmanwithinasingleuniquelegalstructure,(Fig.3.3).IncompliancewiththeEUregulations,theBodiesresponsibleforpathallocationandinfrastructurechargeshavebeencreatedoutsidetherailwaycompany.

Fig.3.3.TheIntegratedmodel

3.7.2.TheSemi-integratedmodelwithapparentorganicseparation

ThismodelisappliedinFrance,andisbasedsimultaneouslyonaninstitutionalseparationofresponsibilities,assetsandliabilities,leadingthereforetoseparatedbalancesheetsandoperatingaccountsbetweentheinfrastructuremanager,whichis“RéseauFerrédeFrance”(RFF)andtherailwayoperator,whichis“Société

NationaledesCheminsdeFerFrançais”(SNCF),(Fig.3.4).However,ifresponsibilities,objectives,strategiesandfinancialissuesconcerninginfrastructuremanagementaredevolvedonRFFasaninfrastructuremanager,themaintenanceofinfrastructureiscarriedoutbySNCF,aconsequenceofapublicsubcontractsignedbySNCFandRFF,SNCFactingasthesubcontractorandRFFfixingtherulesinthismatter.Concerninginvestments,ifRFFisnormallythecontractingauthoritydefiningthescope,consistenceandtheobjectivesofinfrastructureinvestments,SNCFisentitledtoworkasanexecutor.Consequently,thisorganizationofresponsibilitiesdidnotbringaboutanyseparationofthemanpowerforcewithinSNCF,someoftheworkersworkingonoperation’sissuesandothersassubcontractorsofRFF.AsfarastheapplicationofEUDirective12/2001isconcerned,SNCFhasreluctantlyhadtorelinquishanyresponsibilityonaccesschargesissuesandpathallocation,andtheseresponsibilitieshavebeentransferredtootherbodiesformedwithinRFF.

Fig.3.4.TheSemi-integratedmodelwithapparentorganicseparation

Thismodel,whichonlypretendedtoapplytheEuropeanlegislation,whilekeepingintacttheunifiedrailwaysystemofFrance,wascondemnedbytheEuropeanUnionCourtofJusticeinApril2013.However,asofspring2013thismodelisunderchange.Franceislikelytoestablish(eitherinanintegratedorinaholdingmodel)arealinfrastructuremanager(withapersonnelofaround50,000people,inchargeofmaintenanceandoperationofinfrastructure)andanoperator(inchargeofoperationoftrains).

3.7.3.TheHoldingmodel

ThismodelisappliedinGermany,Italy,Austriaandhasledtoalegalseparationofbusinessresponsibilities,(Fig.3.5).Consequently,everysectorisregardednotjustasanindependentbusinessunitbutalsoasalegalentity,therefore

havingseparateaccounts,balancesandfinancialresults.Independencebetweensectorsisthereforebetterassuredthaninpreviousmodels.Alltheselegallyindependentcompaniesareamalgamatedintoaholdingsystemwithacommonexecutiveboardandachairman.Intheory,thechairmancannotgiveanyorderstotheinfrastructuremanager,whichmustremaincompletelyindependentandimpartialtowardsoperators,withnodiscriminationwhatsoever.Theactivitiesandresponsibilitiesoftherailwayoperatorandtheinfrastructuremanagerwithintheholdingcompanyshouldbecompletelyseparate.Pathallocationandaccesschargingissueshavebeensofarkeptwithinthedomainoftheinfrastructuremanager,whomustdemonstratethathisapproachisnotdiscriminatory.Suchaholdingorganizationhasgeneratedthecreationofalotofsubsidiariesandarapidliberalizationoftherailwaymarket.Thereweremorethan520newrailoperatorsin2012inGermany,havingashareof26.0%intherailfreightmarketandabout14.1%inthepassengermarket(in2011).Thoughtheholdingmodelhasbeenstronglycriticized,theEuropeanUnionCourtofJusticeinadecisionin2012judgedthattheholdingmodeliscompatiblewiththeEULegislation.

Fig.3.5.TheHoldingmodel

3.7.4.TheSeparatedmodel

Thismodelisbasedonacompleteinstitutionalseparationoftheformerintegratedrailwaycompanybetweentheoperatorandtheinfrastructuremanager,(Fig.3.6).Pathallocationandaccesschargingissuescanremainwithinthedomainoftheinfrastructuremanager.AtypicalexampleofthismodelisSweden.

Fig.3.6.TheSeparatedmodel

3.7.5.TheSeparatedmodelalongwithfurtherseparationininfrastructure

ThismodelhasbeenappliedintheNetherlandsandisbasedonacompleteseparationbetweentheinfrastructuremanager,ontheonehand,andthevariousactivitiesconcerningoperationoftheformerDutchrailwaysontheother,(Fig.3.7).Inaddition,therewasaseparationintheorganizationoftheinfrastructuremanagerintothreeindependentparts,thefirstbeingresponsibleforpathallocationandaccesscharging,thesecondformaintenanceactivitiesandthethirdfortheplanningofinfrastructureactivity.However,manydisputesbrokeoutbetweenthesedifferentbodies,whosegoalsandlimitswerenotclear.Inordertoresolvethematter,theDutchgovernmentdecidedtosettletheissuebyappointinganinfrastructuremanager,afactthatbringstheDutchmodelclosertothefullyseparatedone.

Fig.3.7.TheSeparatedmodelwithfurtherseparationininfrastructure

3.7.6.TheSeparatedmodelalongwithprivatization

ThismodelisappliedintheUnitedKingdomanditisinspiredbytheSwedishmodelofacompletelegalseparationoftheinfrastructuremanager’sresponsibilitiesandthoseofoperation,withinadditionaprivatizationofalltheactivitiesconcerning,(55):i.theRailwayUnd

ertaking,thatwassplitupinto25operators(calledTOCs)inthepassengersectorandanumberofoperatorsinthefreightsector.Butevenasprivatecompaniestowhichregionalfranchiseshavebeenallocatedthroughcallsfortender,theseTOCshavesurvivedsofarthankstoimportantsubsidiesgrantedbynationalauthoritiesandwhoselevelispartofthecontract(seealsosection6.10.7),

ii.theInfrastructureManager,withtheformationofRailtrack,whichhastriedtorendertherailinfrastructureactivityprofitablebydrasticallycuttingmaintenanceandoperationcosts.SeriousfinancialproblemsofRailtrackledtheBritishgovernmenttoapartialre-nationalizationofinfrastructure,whosedutieshavebeentakenoverbyNetworkRail.

IthasbeenarguedthattheprivatizationofallsectorshasbeenchosenintheUKprincipallytorenderderegulationirreversible.Thus,BritishrailwayreformhasplacedtheStockMarketattheheartofthenewrailwayorganization.

Recentevolutionsconcerningtheinfrastructuremanagerhavebeencharacterizedbyanewinvolvementofthestate,somethingthatprovesthatitishardtoreachanefficientprivateinfrastructureinrailways.

Fig.3.8.TheSeparatedmodelwithprivatization

3.7.7.Assessmentofthevariousmodels

TheIntegratedmodelscorrespondmoretorailwaysthathaveexperiencedinterventionistgovernmentpolicyforalongtimeandemphasizemoreoncooperation.Thechangesastothecurrentsituationarefewandinanycasenotfundamental.

TheHoldingandSeparatedmodelscorrespondtoacompetitivetransportmarketwiththeentryofmanynewrailwayoperatorsandthustheyputemphasisoncompetition.Thesemodelspresupposefundamentalorganizationalchangesandcanboosttheestablishmentofanewcompetitiverailwaythatwillbeeasilyadaptedtothemarketrequirements.Thereiscompetitioninthefreightandlong-distancepassengermarkets,whereaslocalpassengerservicesareawardedbypublicbiddings.

TheSeparatedmodelswithfurtherseparationcanbeconsideredasa

variationoftheSeparatedone.However,thesplitofinfrastructureinmanyunitsmayproveinefficient.

TheSeparatedmodelwithPrivatizationaimedatadrasticreductionofcostsandsubsidies.Eachrailwayoperatorisaprivatecompany,whichmonopolizesrailwayservicesinspecificroutesandissubsidizedbythestate.Thismodeldidnotencouragecompetitionconsiderablyandseriousproblemsofcooperationamongoperatorshaveemerged.

However,anyevaluationofreformsshouldtakeintoaccounthistorical,geographicalandeconomicparticularitiesofeachcase.

Therefore,thedegreeofliberalizationandsegmentationeitheroftheoperationorofinfrastructuremaybecategorizedasfollows:Operation:–Onenationaloperator.–Oneprincipaloperator+regionaloperators.–Manyoperatorsbysegmentationofthenetwork.–Manyoperators–Openaccess.

Infrastructure:–Businessunitwithinanintegratedrailwaycompany.–Aseparatedinfrastructurecompanyeitheramalgamatedwithinaholdingsystemortotallyseparated.

–Infrastructurecompanytotallyprivatized(buttheBritishexperiencehasprovedthatthismodelcannotworkefficiently).

NocountryinEurope,however,hasadoptedtheextremecaseofopenaccesswithatotalprivatizationofeachsector.

Afirstevaluationoftheimpactofreforms(takingintoaccountthatrailwayisaheavyindustryandneedssometimeforreformstobringresults)canbeconductedbycomparingamoreliberalizedmodel(Germany)withalessliberalizedone(France),withtheexaminationofperformances(traffic,productivity,personnel)between1996÷2011,(Fig.3.9).Infact,personnelandproductivitylevelshadsimilarratesofevolutioninbothcountries.PassengertrafficincreasedmorerapidlyinFrancethaninGermany.Incontrast,freighttrafficincreasedinGermanybutcollapsedinFrance,aresultofdifferentrestructuringpatternsinthesetwocountries.However,itisdifficulttocalculatehowmuchoftheresultscanbeattributedtothereforms.Ontheotherhand,thequalityofserviceforpassengersdoesnotseemtohavechangeddramaticallyasawhole.

Fig.3.9.Evolutionoftraffic,personnelandproductivitybeforeandaftertheseparationofinfrastructurefromoperationinGermanandFrenchrailways,(compiledfromdataof(1))

Experiencesfromthederegulationofothersectors,suchastelecommunicationsandelectricity,showthatcommonresultsaremergersandconcentration.Thisevolutionisslowlyemergingintherailsector;forinstance,thethreefreightoperatorsatthebeginningofprivatizationintheUnitedKingdommergedfinallyinone.

Inconclusion,competitionisstillpartialintheEUrailsector,regulationprovesdifficultandtherearefewnewentrantsinmostcountries.

3.8.RaillegislationintheUSAandCanada

Asanalyzedinsection1.8,railwayshaveamarginalroleinthepassengermarketintheUSA(withashareof0.4%in2010)butplayanimportantroleinthefreightsector(withashareof42.6%in2010).AmericanraillegislationshouldbeexaminedwithinthecontextoftheNorthAmericanFreeTradeAgreement(NAFTA)betweentheUSA,CanadaandMexico.

AnothercharacteristicoftheAmericanrailmarketisthattheprincipalrailoperatorscanownthetracktheyarerunningon.AscompetitionistheruleintheAmericaneconomy,legislationtriedtoassurerightsofrailoperatorstorunoninfrastructureownedbyanother(andoftencompetitor)operator.

Railwaysoperatedinboththepassengerandfreightsectorasprivatecompaniesuntil1970,whentheNationalpassengerrailroadcorporation(Amtrak)wasformed,afederallyownedcorporationsubsidizedbythefederal

government.AmtrakownsthetrackinfrastructureitusesintheNortheastoftheUSAandhastherighttooperateoverallothertracksundernegotiatedaccessagreements(subjecttoadjudicationintheeventofdisputewiththeinfrastructureowner).

Duringthe1970s,about20%oftherailwayindustryfacedbankruptcyintheUSA.Thus,theConsolidatedrailcorporation(Conrail),ownedbythefederalgovernment,wasformedin1976,resultingfromtheconsolidationofthebankruptcompaniesintheNortheastandMidwestoftheUSA.TheoptionwastomakeConrailviableandthentosellit.Ifitwerenotpossibletomakeitviable,itwouldbeliquidated.Conrailwassoldin1987(havingsufferedconsiderablelosses).

ThemoreimportantmeasureinresponsetothecontinuingfinancialcrisisintherailindustryintheUSAwasderegulation,whichwasintroducedbythesocalledStaggersActof1980,withtheobjectivetoachieveabalancebetweenthefinancialviabilityoftherailsectorandtheinterestsoftheshippers.

RegulationofthetransportsectorintheUSAwasconductedbytheInterstateCommerceCommission,whichwascreatedin1887andreplacedin1995bytheSurfaceTransportationBoard,whosejurisdictioncoversallrailwaysoperatingwithintheUnitedStatesandhasdutiesto,(53),(62):–ensurethatrailcarriershavetrackagerightstooperateonanothercarrier’sinfrastructure,

–reducetariffs,particularlywhencomplaintsformarketdominanceandpowerhavebeenaddressed.In2011itwasreportedthattheStaggersActledtoa51%reductioninaveragefreighttariffs,(53),

–addressquality,–controlexit,underspecificcircumstances,fromthemarket,–approveordeclinemergersintherailindustryorimposeconditions(i.e.trackagerights)onthemerger,topromotecompetition.

Thislegislationseemstohaveworkedwellinpreservingcompetitionoverall,althoughcasesofdisputesrevealedthemany,moreorless,subtlewaysinwhichtheownerofinfrastructurecancreatebarrierstotheentryofanotheroperator,whenaccessexistsintheory.

AmajordebateintheUSAintheseconddecadeofthe21stcenturyfocusesonwhethertherailmarketissufficientlyderegulatedandre-regulationmeasuresshouldeventuallybetaken,whichisthepositionoftheAmericanrailroadcorporation.

RailwaysinCanadaalsohaveonlyfreighttraffic(withashareof67.9%in

theirnationalfreighttraffic),whichisrealizedatapercentageofabout85%bythetwomaintrans-continentalrailways,CanadianNationalandCanadianPacific.

CanadabegantoderegulaterailwaysbeforetheUSAwiththeNationaltransportationactof1967,whichchangedin1987.Subsidieswereterminatedin1996andlaborproductivityafterderegulationincreasedby93%from1988to1997.

3.9.RaillegislationinJapan

StrongdensitiesofpopulationinJapan(with1,500peoplelivingperkm2ofhabitablearea,against160inFrance,260intheUnitedKingdomand50intheUSA),favorrailpassengertraffic.Onthecontrary,freighthasarathermarginalshare.JapaneseNationalRailways(JNR)startedfacingseriousfiscalproblemsinthemid-1960s,whichhadnotbeenovercomefortwodecades,inspiteoffourrestructuringplans.

Inordertopursuethefasteconomicgrowthandrisingpersonalincomeofthecountry,Japaneserailwaysinvestedhugeamountsofcapital.However,railinfrastructureisextremelycostlywithalowrateofreturn.Debtincreasedgreatly,increasesinfaresresultedinfewercustomers,andprivatizationandsegmentationwereseenastheonlywaytorevitalizetheJapaneserailways.

Thewholerailnetworkwassplitin1987into6regionalpassengercompanies(eachoneowningitsowninfrastructure)totallyprivatized(JRHokkaido,JREast,JRCentral,JRWest,JRShikoku,JRKyushu).Anothercompany,Japanfreightrailways,whichpaysfeestothe6railpassengercompaniesforusingtheirtracksandotherfacilities,tookfreighttraffic.

Beforederegulatingandprivatizingtherailmarket,theJapanesegovernmentundertookspecificmeasures:thetransferofJNR’slong-termdebttotheJNRSettlementcorporation,thereductioninexcesslabor(from400,000in1980to191,000in1994),andtheabandonmentofunprofitablelocallines.

Theratiooflaborandcapitalcoststofareincomedecreasedgreatly,(Table3.2),(64).Thenumberofpassengersincreased(afterprivatization)in1993by20%comparedto1986.Therollingstockkilometerstraveled,alsoincreasedabout20%afterprivatization.However,thelonger-termissueofthefundingoffuturemajorrailinfrastructureprojectshasnotbeenresolved,(64).

Table3.2.

RatiooflaborandcapitalcoststofareincomebeforeandafterprivatizationofJapaneserailways,(64)

Since2006,allsharesofJREast,JRCentralandJRWesthavebeentradedintheStockMarket.Ontheotherhand,allsharesofJRHokkaido,JRShikoku,JRKyushuandJRFreighthavebeentransferredandareownedbytheJapanRailwayConstruction,TransportandTechnologyAgency,anindependentadministrativeinstitutionofthestate.

Almost25yearsafterthederegulationandprivatizationAct,morethan130railpassengeroperatorsand30railfreightoperatorsarestronglycompetingintherailmarketofJapan.

3.10.RaillegislationinChinaandIndia

InbothChinaandIndiarailwayactivityistotallyregulated.RailwaysinChinaarepubliclyownedandcontrolledbytheMinistryof

RailwaysofChinaInfrastructurebelongstothestateandmajorissuesconcerningtariffs,serviceplanning,andinvestmentaretakenbythegovernment.With2millionemployees,Chineserailwaysaregeographicallysplitinto16bureaus,eachonecoveringaparticularregionofChina.Therearefears,however,thatcompetitionfromtheroadsectorandlowprofitratescombinedwithahighlyregulatedenvironmentmayleadtolowrailprofitability.

IndianrailwaysisanIndianstate-ownedcompany,ownedandoperatedbythegovernmentthroughtheMinistryofRailways.PrincipalrailwaylegislationcanbefoundintheRailwaysActof1989,whichisamendedregularly.With1.4millionemployees,Indianrailwaysaredividedintoseveralzones(16in2013),whicharefurthersub-dividedintodivisions.

3.11.RaillegislationinAustraliaandNewZealand

RailwaysinAustraliahavedifferencesfromonestatetoanotherconcerningbothgaugeandorganization.Thegaugeproblemwasresolvedpartlybytheconversionofallinterstatetrackstostandardgaugein1995.Railpassengertransportislimitedoutsideofthemajorcities,becauseoflongdistancesinasparselypopulatedcountryof21.7millionpeople(in2012).Thus,railwaysinAustraliafocusprincipallyonfreight.

Untiltheearly1990s,railwaysoperatedasverticallyandhorizontallyintegratedpublicsectormonopolies.After1995andthecreationoftheAustraliancompetitionandconsumercommission,policyaimedattheintroductionofcompetitioninrailoperationswithasakeyfactortheconditionsofaccesstorailinfrastructure,whichcanbedonein3ways:declarationunderthenationalaccessregime,certificationofthestateregime,andtheauthorizationofanundertakingfromaninfrastructureprovider.Concerningsafety,anationalrailsafetylawandanationalsafetyregulatorhavebeenestablishedin2009andthespecificlawwasafterwardsdetailedinthevariousAustralianstates.

ThestatesofWesternAustraliaandQueenslandowntheverticallyintegratedsystemsandhavecreatedseparatebusinessunitsandseparateaccounts.ThestatesofVictoriaandNewSouthWaleshaveseparatedinfrastructurefromoperationandfreightfrompassenger,(62).

LegislationinNewZealandwasveryprotectiveforrailwaysanduntil1961carriageofgoodsbyroadwaslimitedtodistancesupto50km,whichwasraisedto67kmin1961andto150kmin1977.Liberalizationoftheroadhaulagein1983pressedrailwaystowardrestructuring.Infrastructureandrollingstockweretreatedasseparateaccountingunitssupportedbyaninternalpricingstructure.Thelaborforcewasreduced,trafficwasmaintainedandproductivityincreased.

*Liberalizationisaneconomico-politicalvisionoftheorganizationoftheeconomysuggestingthatthestatedoesnotinterfereineconomicaffairesandthattherealrulershouldbemarketforces.Deregulationisaneconomictechniquesuggestingthewithdrawalofregulationsandofstateinterventionsinthemarket.Deregulationisusuallyameasuretowardsliberalization,othermeasuresbeingtoavoidanycontrolofpricesandsalaries,anti-trusttechniques,etc.Letusnoticethatattherailwayfield,characterizedbyagradualliberalization,regulationisstillinforce.Inanycase,eveninatotallyliberalizedtransportmarket,aminimumregulationconcerningsafety,levelofservice,financialcapacityofinvolvedcompaniesisnecessary.

4ForecastofRailDemand

4.1.Purposes,needsandmethodsfortheforecastofraildemand

Forecastisanefforttoforeseeandanticipatedevelopmentsinthefuture.Itisacomplexprocedurethatmusttakeintoaccounttheexpectationsandtendenciesofthesocietyinquestion,thesituationintheindustry,economicandpoliticalfactors,humanfearsandthepsychologyofthehumanbeing.Forecastoffuturedemandisaprerequisiteformanyrailwayactivities,suchas:–constructionofanewrailwayline(orstation),–opening(orclosing)ofanewrailwayservice(e.g.high-speedservices,commuterservices,etc.),

–buyingofrollingstockvehicles,–programmingofthenecessarystaffintrainsandstations,–revenueestimation,–commercialandpricingpolicy,–managementstrategies.

Conductingaforecastisadifficulttask.Parametersaffectingdemandareofbothtechnologicalandhumannature,thelatteronesbeingdifficulttoforesee;theformoftheirintercorrelationiscomplexandstatisticaldataconcerningpastdemandareofteninsufficientorinaccurate.

Allrailtransportforecastsarebasedonakindofraildemandmodel.Amodelcanbedefinedasahumaneffort(throughasimplifiedrepresentation)tounderstand,explainandforeseetheevolutionofaphysical,humanorsocialphenomenon.Ittriestoinvestigatewhetheracausalinterrelationshipcanbefoundbetweenthephenomenonunderstudy(e.g.numberofhigh-speedtrainpassengersbetweenLondonandParis)andtheparametersaffectingit(yearofthestudy,costofrailtransportandofcompetingmodes,traveltimesbyrailandcompetingmodes,qualityofservice,GrossDomesticProduct,etc.).Onceacausalrelationisestablishedandthestatisticalandlogicalvalidityofthemodelischecked,thenthemodelcanbeusedfortheforecastoffutureraildemand.

Amodelcanbebasedondifferentmethodologiesofthephenomenonunder

studyandthuswecandistinguishthefollowingcategoriesofmethods:–qualitativemethods,–statisticalmethods,–quantitativeorcausalmethods(econometric,gravity),–fuzzyandneuralmethods.

Whenforecastingraildemand,wedistinguishtheshort-termlevel(6÷24months),medium-termlevel(2÷5years)andlong-termlevel(5÷10years).Amodelcanbeappropriateforshort-ormedium-termforecastbuttotallyinappropriateforlong-termforecastandvice-versa.

However,amodelcanexplainonlyasmallcategoryofspecificproblems.Itistheresultofanumberofassumptionsandshouldnotbeextended,generalizedorusedforcasesforwhichtheassumptions,uponwhichitisbased,donothold.Railspecialistsshouldavoidsuchinappropriateextensionsandgeneralizationsofmodels.

Aforecastmodelshouldnotnecessarilyhaveacomplicatedform,justtheopposite.Withintheacceptablelimitsofaccuracy,thesimplestformofmodelshouldbethetarget.

Anydemandforecasthasinherentweaknessesanduncertaintiesandshouldclearlyaddressassumptionsonwhichitisbased,thedegreeofaccuracyoftheforecasts,andtheframeandconditionswithinwhichtheforecastcanbeused.

Ontheotherhand,forecastingpresumesaminimumofstability.Theforecasterconsidersmanyparametersthatwillcontinueanevolution,whichisinfluencedbythepast.Theforecastercanforecastwhatmaybelikelytooccur,buthecannotpredicttheunpredictable.

4.2.Parametersaffectingthevariouscategoriesofraildemand

4.2.1.Parametersaffectingraildemandglobally(aggregateapproach)

Theneedforrailtransportisnotanendinitselfbutamediumtosatisfyotherhumanneeds.Thedemandfortransportisderived.Withtheexceptionofsightseeing,peopletraveltosatisfyanotherneed(work,leisure,meetingotherpersons,shopping,etc.)attheirdestination.Theneedfortransportwouldnothaveexisted,ifalltheseactivitieshadbeenlocatedanddevelopedinneighboringareas,somethingthatdidnothappeneveninthefirstformsoforganizationofhumansocieties.Asaresultofeconomicandsocialactivities,transportisstronglyinfluencedbyeconomicfactors.

Railtransportisalsostronglyinfluencedbythespatialdistributionofhumanactivities.Highconcentrationsofpopulationsandgoodsarefavorableforrailtransport.

Railtransporthasadynamiccharacteranddiffersfromdaytodayandfromhourtohour.

Theinstitutionalframeworkhashadaradicalimpactonraildemand.Formanydecades,railwayshadmonopolisticcontroloftherailmarket,facingonlyexternalcompetitionfrombuses,privatecarsandairplanes.However,internalcompetition,thatisoperationofmanyrailwaycompaniesonthesameroute,hasbeenrecentlyintroducedinsomecountries,ashasbeenanalyzedinChapter3.

Thesensitivityofcitizenstotheprotectionoftheenvironmenthasasaresultthatenvironmentalissuesshouldalsobetakenintoaccountamongparametersaffectingdemand.

Technologicaldevelopmentsmaybecriticalforraildemand,aswellasfuelprices.

Theperformanceandcharacteristicsofothertransportmodesalsoaffectraildemand,(73).

4.2.2.Effectsondemandofthevariousparametersofrailtransport

4.2.2.1.Passengerraildemand

Passengerdemandisdividedintointercitydemand(amongcities)andcommutingdemand(fromthecentralpartofacitytoitssuburbsandvice-versa).Intercitydemandcanhaveasamotivationeitherbusinessactivitiesorleisure.Thesameappliestocommuting,butallcomponentsofcommutingdemandhavesimilarcharacteristicsandforthisreasonthereisnodistinctionbetweenbusinessandleisure.

Business,leisureandcommutingdemandareaffectedbythevariousparametersofrailtransport,whichare:costoftravel,traveltime,frequencyofservices,qualityofservices,andpunctuality.Traveltime,punctuality,frequency,andqualityofservicesarecriticalforbusinessraildemand.Costiscriticalforleisure,whereascost,punctuality,andfrequencyaregreatlyinfluencingcommuting,(Table4.1).ThereasonfordifferencesillustratedinTable4.1israthersimple:thecompanyandnotthetravelingpersonundertakesthecostofbusinesstravel,whereasforleisureandcommutingitisthepersonhimselfwhopaysthecostoftheticket.

4.2.2.2.Freightraildemand

Freightdemandis,inmostcases,partoftheindustrialprocess.Parametersthatinfluencefreightdemandare,(22),(94):–typeofgoods:characteristicsandnatureofmaterialsandoffinalproducts,–geographicalparameters:location,vicinitywithaport,densityofpopulation,

Table4.1.Parametersofrailtransportandtheirdegreeofinfluenceforbusiness,

leisureandcommutingdemand

–socio-economicparameters,–legislationandroadtrafficrestrictions,–price.Thepricingpolicyinfreightismoreflexibleandcontainsusuallynegotiationswithclients,

–seasonalityforsometypesofgoods,–terminalandcombinedtransportequipment.

Weusuallydistinguishrailfreightinbulkquantities(oil,cereals,etc.)fromisolatedsmallitems.

Manysurveysamongshippersandtransportforwardershaverevealedthereasonsofpreferenceforrailfreight,whichare:highvolumes,lowcost,non-availabilityofroadvehicles,safety.Thereasonsofnon-preferenceofrailfreightare:highshipmenttimes,bureaucraticprocedures,highcostsanduncertaintyoftimeofdeliveryofgoods,(24).Itisclearthatsomeshippersconsiderrailtariffslow,whereasothersconsiderthattheyarehigh.Thereasonsofpreferenceof

roadtransportbyshippersare:speedofshipment,doortodoortransport,simpleproceduresandflexibility,accuracyofshipment,lowcost,andtheavailabilityofvehicles.Ifrailwayswanttoincreasetheirfreighttraffic,theymustovercomeallthesehandicapsandweaknesses,asrevealedbysurveys,(15),(22).

4.3.Qualitativemethods

4.3.1.Marketsurveys

Thequalitativemethodmostcommonlyusedisthemarketsurvey,whichhoweverrequiresacertaintime(fromsomedaystomonths)andhasahighcost.Themarketsurveyistheonlymethodthatcanbeappliedwhentherearenostatisticaldata(e.g.,theopeningofanewrailwaystationorconstructionofanewrailwayline)orwhenattemptingtoidentifythereactionsofcustomerstocertainchangesortothesupplyofnewrailservices,(91),(92).

Transportmarketsurveys,besidesthedeterminationofpassengercharacteristics,can(bymeansofappropriatequestions)identifypassengerintentions.Indeed,uptothe1980s,transportmarketsurveyswereaboutquestionsovertrendsandchoicesthathadalreadytakenplace.Suchsurveysarecharacterizedassurveysofrevealedpreference.

Duringthepastfourdecades,however,marketsurveysincludequestionsofahypotheticalnature(e.g.“howoftenwouldyouusethetrainiftheticket’spricewerereducedby20%?”).Thustheintentionsofthepersonquestionedareidentifiedandsomeindicationsareprovidedregardingthedevelopmentoffuturedemand.Suchsurveysarecharacterizedassurveysofstatedpreference,(91).

Table4.2givesasampleofaquestionnairethatwasusedinamarketsurveyforintercitytrains,(80).

4.3.2.Scenariowritingmethod

Thesearchforalternativequalitativeapproachesforlong-termforecastsresultedinthedevelopmentofthescenariowritingmethod.Thismethodcanbeusedformedium-andlong-termforecasts.

Ageneraldefinitionofthemethodisthatthroughthewritingofscenariosoneattemptstopresentthepatternthroughwhichcertainconditionswillformulateinthefuture,usingasapointofreferenceandcomparisontheexistingsituation,whichisdescribedthroughaseriesofeventsandconditions,(74).

TheScenariowritingmethodisamongthemethodsusedforlong-term

forecastsoftheEuropeanCommission(optimistic,baseline,andpessimisticscenarios)aswellasinstudieswithalong-termrange.

4.3.3.Delphimethod

TheDelphimethodisusedtoforecastcertainmedium-termeventsandtocalculatetheprobabilityoftheirhappeninginthefuture.Morespecifically,theDelphimethodhasthreeseparatestages:thepreparatorystage,thestageofcontrolledfeedbackmechanismandthefinalstageofconclusionsandforecast.

Asanexample,theDelphimethodisusualatthescheduledmeetingsofinternationalrailinstitutions(suchastheInternationalUnionofRailways),wherefuturepolicies(andtheprobabilityforthemtooccur)arediscussedamongspecialists.

Table4.2.Questionnaireforamarketsurveyonintercitytrains,(80).

4.4.Statisticalprojections

4.4.1.Theoreticalbackgroundandconditionsofapplicability

Statisticalprojectionisthemethodmostcommonlyusedamongrailwaysforaquickestimationoffuturedemand.Basedonstatisticaldata(whichshouldcoveratleast10years),aprojectionofthepast’strendsintothefuturecanbeconducted,whichrequiresfromsomehoursto1÷2daysofworkandhasalowcost.Themethodgivesadequatelyreliableforecastsforaperiodofupto2÷5yearsaftertheprojectionyearaslongasnounpredictableeventstakeplace(suchasasuddenchangeintheeconomicsituationoroftheconditionsofcompetition,accidents,etc)andsupplyremainsunchanged.

Themethodisbasedontheassumptionthatallparametersaffectingrailtransportdemandoveraspecificroute(traveltimes,fares,income,elasticities,etc.)willcontinueoverthecourseoftimetoaffectrailtransportinthesamemanner.Thiscanbeacceptableonashort-termormedium-termlevel,buthardlyonalong-termone,(71).

Manyrailwaysbegintheirforecastingbyusingstatisticalprojections,whichcanthenbeimprovedwiththeresultsofamarketsurveyoraneconometricmodel.

Dataaresetonademand(Y-axis)–time(X-axis)diagram(Fig.4.1).Thisdiagramprovidesafirstindicationwhetherthedevelopmentofthephenomenonislinearorexponential.

Thus,ifthephenomenondevelopslinearly,demandYtfortheyeartwillbe:

Ifthephenomenondevelopsexponentially,demandforyeartwillbe:

Fig.4.1.Statisticaldata(yi)andregressionline(Yi)

Itshouldbenotedthatrailtransportdemandmayhavealineardevelopmentoveritsbeginningandanexponentialdevelopmentlateron,oranexponentialdevelopmentduringitsbeginningfollowedbyphenomenaofsaturation(anasymptoticdevelopmentlateron).Inthiscase,acombinationoftheaforementionedformulasshouldbeapplied,(71).

Calculationofparametersa,b,c,dofequations(4.1),(4.2)willbetheresultofaregression(eitherlinearorexponential)ofthedependentvariableYt,withregardtothesingleindependentvariablet.Therefore,wecandeterminethestraightline(forlineardevelopment)orcurve(forexponentialdevelopment)fromwhichthevariouspointsofFigure4.1aretheleastdistancedfrom.Thisisachievedbyemployingthemethodofleastsquares.

Letyibethevariousvaluesgivenbystatisticaldata, theaverageofvaluesyi,andYithevaluesprovidedbythecurveofFigure4.1.Whetherthecurveissatisfactorilyadjustedtothestatisticaldataofthepastwillbedependentuponthecoefficientofdetermination,R2,whichisdefinedas:

Thecoefficientofdeterminationmultipliedby100giveshowcloselytheforecastcurveapproachesstatisticaldata.ValuesofR2approaching1.0showthattheregressioncurveissatisfactorilyadjustedtothestatisticaldataofthepast,whereasR2valuesapproachingzeroshowthatnosatisfactorycorrelationinthepast’sstatisticaldata,whichpresentirregularfluctuations,canbefound.For

mostdemandforecasts,valuesofR2>0.90areconsideredsatisfactory(71),(74).Aplethoraofcomputersoftwareallowsaquickandeasycalculationofthe

parametersa,b(orc,d)oftheregressionequation*.Thesecomputerprogramsallowtheuseofvariousfunctionforms(linear,polynomialorexponential),forwhichthevariousstatisticalindices(coefficientsofindependentvariables,dataaverages,samplevariance,coefficientofdetermination,etc)aredetermined.

Anumberofquestionsareraisedregardingthemethodologyoffutureprojectionbyusingexistingstatisticaldata,(71),(77):•whatisthetimeperiodthattheavailabledatashouldcover?Asderivedbyanumberofanalyses,10yearsistheminimum,providedthatstatisticaldatarepresentsufficientlytheevolutionofdemand,

•howfarintothefuturecanthepast’sdatabeprojected?Itwasconcludedthattheprojectionperiodcouldnotexceedhalftheanalysisperiod,aslongasthefundamentalassumptionthattheparametersaffectingdemandinthepastwillremainthesameinthefutureandwiththeirdegreeofinfluenceunchanged,whilstthecharacteristicsofsupplyremainunchanged.

4.4.2.Exampleofastatisticalprojection

Considerforinstanceaneffortinyear2012touseastatisticalprojectionfortheforecastofdemandofpassengersforEurostartrains,(seesection2.4.2),betweenLondonandParis.Thefirststepistocollectdatathatshouldbereliable.PointsinFigure4.2aretheannualnumbersofpassengersbetween1995÷2011,collectedfromtheinternetsitewww.eurotunnel.com.

Fig.4.2.DataofannualdemandofpassengersofEurostartrainsandlinear(—)and2nddegree

polynomial(––)regressioncurves

OrdinatesofdemandfortheEurostar,asillustratedinFigure4.2,donotmakeclearwhetherthephenomenonunderstudydevelopslinearlyorexponentially.Forthisreason,bothalinearandanexponentialregressionwillbeattempted.

Firstwetryalinearregression(Fig.4.2,line–)andweenterthedataofFigure4.2inacomputersoftwareinordertocalculatethecoefficientsofthelinearregression:

whereDt:demandfortheyeart.

Thecoefficientofdeterminationforthelinearregressionofequation(4.4)isfoundtobeR2=0.86,whichisaquitehighvalueasitapproaches0.90andallowsatrustworthyforecast.

Nextwetryanexponentialregression(Fig.4.2,line–––),forwhichfuturedemandDtcanbecalculatedaccordingtotheequation:

Dt=-4,812.23·t2+1.95956·t-1.1936·108

ExponentialregressionrendersanequallyhighvalueforthecoefficientofdeterminationR2=0.87.

Whichcurveshouldtheforecasterchoose?Thereisnoapriorianswertothisquestion.Ofcourse,theforecasterwilllookforacurvewiththegreatervalueofthecoefficientofdeterminationR2.Butinourexamplebothcurves(linearandexponentialregression)havealmostexactlysimilarvaluesforR2.Thustheforecastershouldconsiderwhichofthecurvesforequations(4.4),(4.5)isclosertothephenomenonunderstudy.Indeed,alinearevolutionpresupposesconstantratesofyearlyincreases,whichofcoursecannotcontinueforever.Anexponentialevolution,whichbeginsexponentiallyandthenturnsasymptoticallymaybeclosertoreality.Thereforeitisapparentthatinadditiontoagoodstatisticalanalysis,experience,intuitionandimaginationarealsoessentialinordertoputtogetheragoodforecast.

However,iftheforecasterexaminesthedatacarefully,hecanremarkthatthefirstfullyearofoperation(1995)hasaverylowdemand.Forthisreason,thedataforthisyearcouldbeomitted.

Howlongcanthisforecastbeused?Toachievestatisticallyaccurateforecasts,theperiodofforecastshouldnotexceedhalfoftheperiodcoveredbythestatisticaldata,thatis7÷8years.

4.5.Econometricmodels

4.5.1.Definitionanddomainsofapplication

Econometricmodelscanprovideacausalcorrelationbetweentheexpecteddemand(dependentvariable)andthecauses(independentvariables)affectingit.Econometricmodelsrequiretime(fromsomedaysto1÷2months)andarecostly;thereforetheyareusedonlybylargerailwayauthorities,stateservicesoruniversityinstitutes.

4.5.2.Statisticaltestsforthevalidityofaneconometricmodel

Thestatisticalvalidityofaneconometricmodelistestedbymeansofanumberofstatisticalanddiagnostictests,whichare,(75),(76),(79):–collinearitytestofindependentvariables,–statisticaltestofthestandarderror,–firstdegreecorrelationtesttoresidualsthroughDurbin’s-hstatistics,–residualcorrelation,heteroscedasticityandnormalitytest,–modelfunctionformtest,–checkofresidualsinrelationtostandarderror,–modelstabilitytest.

4.5.3.Examplesofsomeeconometricmodels

Asanexample,therewillbegivenaneconometricmodel,whichwassuggestedfortheforecastofannualrailwaypassengerdemandinGreece.Theanalysisperiodspansovertheyears1960÷2000.Variablesexpressedinmonetaryunitshavebeenadjustedaccordingtotheannualconsumerpriceindex.Allvariablesareincorporatedintothemodelasindicesthathavethevalue100fortheyear1980(medianyearoftheanalysisperiod).

Theeconometricmodel’sequationis,(77),(82):

where:Dr :railpassengerdemand/population,

cr :unitcostoftransportbyrail(perpassenger-kilometer),

Ico :carownershipindex,

cb,r :competitionvariable,expressedastheratioofunitcostbybustotheunitcostbyrail,

GDP :GrossDomesticProductofGreecepercapita,d78 :dummyvariablefortheyear1978,whenGreekrailwayschanged

theestimationmethodofticketssoldinthetrain,Dr(-1) :atimelagdependentvariable,theuseofwhichrepresents

constraintsonsupply(servicefrequency,railcapacity,qualityofservicesinstationsandontrains,etc).

Themodel’sadjustmenttorealdataissatisfactorywithacoefficientofdeterminationR2equalto0.89.

Figure4.3illustratestheeconometricmodel’sresultscomparedtodata(actualvalues).

InasimilaraggregateapproachtoforecastdemandforinterurbanrailtravelinIreland,thefollowingindependentvariableswereselected:railfares,income,carownership,qualityofservice,consumerexpenditure,seasonality.Theeconometricmodelhadtwoforms:onelinearandonelogarithmic.However,thecoefficientofdeterminationwashigherinthelinearthaninthelogarithmicapproach,showingthatinthiscaseachangeinanyindependentvariablehadalineardirecteffectondemand,(93).

Othereconometricmodelsfortheforecastofdemandoflocalrailservicesandstationshaveidentifiedthefollowingindependentvariables:railfares,railservicelevel,journeytimes,frequency,costsandservicelevelsofcompetingmodes,andeconomicactivity(GDP),(89).

Fig.4.3.Comparisonofresultsoftheeconometricmodelwithrealdata,(77).

4.5.4.Exogenousandendogenousvariablesinraileconometricmodels

Independentvariablesinaneconometricmodelmaybedividedintotwocategories:exogenous,whicharenotaffectedbytherailindustry,endogenous,whichareaffectedbytherailindustry.

Inarecentmanualofrailpassengerdemandforecast,exogenousandendogenousvariablesareidentifiedasfollows,(72):–exogenousvariables:GDPoremployment,population,carownership,carfuelcosts,carjourneytimes,buscost,busjourneytime,busheadway,aircost,airheadway,andmetrocost,

–endogenousvariables:•railfares,•railgeneralizedjourneytimes(incorporatingin-vehicletime,frequencyandinterchange),

•railqualityofservice,•non-timetablerelatedservicequality(stationfacilities,rollingstockfacilitiesandenvironment).

4.6.Gravitymodels

Gravitymodelscanbeusedincasessuchasnewrailstationsortheconstruction

ofanewrailwayline,forwhichthereareobviouslynostatisticaldata.Fortheforecastofdemandofanewrailwaylinebetweencitiesiandj,it

wassuggestedthatthegeneralgravityformulabespecifiedasfollows,(92):

where:Dij:raildemandbetweencitiesiandj,

Ai: populationofcityi,

Aj: populationofcityj,

dij: distancebetweencitiesiandj,

k: proportionalityfactor.

Equation4.7presentstoosimplisticananalogywiththelawofgravity.Forthisreason,ithasbeenimprovedbyreplacingpopulationwiththetotaltransportdemandofeachcity,anddistancebythegeneralizedcostofrailtransport:

where:Dij:raildemandbetweencitiesiandj,

Ai: totaltransportdemandofcityi,

Aj: totaltransportdemandofcityj,

Cij: generalizedcostofrailtransportbetweencitiesiandj,

a: parameterofcalibration.Variousstudiesestimatedvaluesoftheparameteratobebetween0.6and3.5,(74),(90),

k: proportionalityfactor.

4.7.Fuzzymodels

4.7.1.Descriptionofthefuzzymethod

Fuzzylogiccomesfromtheareaofmathematicaltheoryknownas‘fuzzygroups’.IncontrasttothebasicAristoteliantheory,whichacceptsonlytrueorfalsestatements,(Fig.4.4a),andisexpressedincomputersthroughthebinary

systemwith0or1,fuzzylogicisinapositiontoexpresstermssuchas‘perhapsfalse’or‘moreorlesstrue’,(Fig.4.4b).Fuzzylogic,whenusedincomputers,allowsforthesimulationofthehumanthinkingprocess,theexpressionofquantitativelynon-specificinformation,thuspermittingdecisionsandfinalconclusionstobebasedonvagueandincompletedatawiththeuseofaprocessofgradualfuzzinessreduction.

Fig.4.4.From‘trueorfalse’logicto‘fuzzy’logic

Mathematicaltheorydescribesthecorrelationoftwovariablesbyusingfactorssuchasthecoefficientofdetermination(R2),standarddeviation(ó)andsamplevariance(var),whiletheerrorinherentinthevariables’correlationiscarriedontotheforecast.TheaforementionedFigure4.1showsthatthedependentvariableYcouldhavealinearcorrelationwiththevariableX.Weobservethattheregression’slinepassesthroughvariouspoints,givenbystatisticaldata,withoutbeingabletoexplainthepositionofeachoneseparately.Theinformationlostinthismanneraffectstheforecastingeffort,(84),(87).

Afuzzylinearregressionmodelhasthefollowingform:

whereAiaresymmetricalfuzzynumbers,i=1,..,n.

AfuzzynumberAisspecifiedasA=(r,c)L,whereL(x)iscalledareferencefunctionandthenumbersrandcdenotethecenterandthespreadrespectively,(Fig.4.5).Theprobabilityμtakesvaluesfrom0to1.

Thevariouscalculationsofafuzzyapproach(suchasinthefollowingexample)canbeexecutedwiththeuseofMapleV4software(amongothers).

Inadditiontothefuzzymethod,neuralmethodshavebeensuggestedforrailproblems,(81).

Fig.4.5.Characteristicsofafuzzynumber

4.7.2.Exampleofafuzzymodel

Asanexample,afuzzymodelusingthestatisticaldataofFigure4.3,willbegiven.Theanalysisperiodspansovertheyears1960÷2000.

Thefuzzyregressionconcludedthefollowingfuzzyequation,inwhichthefirsttermgivesthecenteroffuzzyregressionandthesecondterm(addedorsubtracted)theupperandlowerbounds,(77):

wherer0,r1,…,r6andc0,c1,…,c6arecoefficientswhicharederivedbythefuzzyregressionanalysis,(Table4.3).

Thecontributionofthefuzzymethodologyconsistsinthereductionoftheambiguityofausualeconometricmodel,throughtheboundsofthefuzzyregressionmodel,(Fig.4.6).

Table4.3.Variablesr0,r1,…,r6andc0,c1,…,c6ofthefuzzymodel

Fig.4.6.Actualvaluesandboundsofafuzzylinearregression,(77)

4.8.Time-seriesmodels

4.8.1.Definitionoftime-seriesmodels–ApproachofBox-Jenkins

Time-seriesisdefinedasaseriesofsuccessiveobservations,whicharesufficientforadescriptionofthephenomenonunderstudy.Theindependentvariableintime-seriesmodelsistimet.

Thesimplestformofatime-seriesanalysisisastatisticalprojection,whichhowever,duetoitssimplicity,isusuallypresentedseparatelyandhasbeenalreadyanalyzedinsection4.4.

Time-seriesmodelstrytoidentifytheformofdevelopmentofthestudiedphenomenoninthepast,toinvestigatewhetherthisevolutioncouldbe,andunderwhatconditions,continuedinthefuture,andfinallytoforecastwhatcouldbeexpectedinthefuture.

Themostpopulartime-seriesmodelreferstothenamesofBoxandJenkins,

whodevisedtechniquesallowingthechoiceamongspecificpatternsofevolutionofaphenomenon,whiletryingtosimulateandtoidentifyeitherthewholephenomenonunderstudyorpartofit.Eachofthesepatternsisdescribedbyamodelsuchas:AR(Autoregressive),ARI(AutoregressiveIntegrated),MA(MovingAverage),IMA(IntegratedMovingAverage),ARMA(AutoregressiveMovingAverage),ARIMA(AutoregressiveIntegratedMovingAverage),andSARIMA(SeasonalAutoregressiveIntegratedMovingAveragewithSeasonality),(74),(85).

TheBox-Jenkinsmodelisrarelyusedforrailwayproblems,asitrequireslotsofdata,iscomplicatedandcannotassurethatacalibrationwillbeachieved.Whenitisused,therailforecastershouldlookfortheappropriatepattern,whichsuitstotheevolutionofdemand.

4.8.2.TheLeastmedianofsquares(LMS)methodfortheforecastofraildemand

Arobustkindofregression,knownas“Leastmedianofsquares(LMS)”regression,hasbeendevelopedsoastoachieveaforecastwithouttheeffectofextremevalues(outliers).Themethodisparticularlysuitedforcaseswheretherearenonnormaldistributions,extremeobservations(outliers)oracombinationofthese,(74),(86).

Thecentralideaofthemethodisthefollowing:thevaluesoftheparametersslopeandintercept*aresuchthatthemedianofnormalizedsquarederrorsisminimized.Theapplicationofthismethodminimizesthemedianofsquaredresiduals,asitacceptsthemedianasmoreresistanttoresidualsthantheaverage,whichdominatessquaresminimizations(ordinaryleastsquaresmethod).

AcharacteristicfeatureoftheLMSmethodisthatthebreakdownpointcorrespondstoa50%percentageofoutliersamongobservations,whichisthehighestpossibleforastatisticalmethod,(Fig.4.7).Thebreakdownpointisthemaximumpercentageofextremeobservationsinthesample,sothattheydonotaffecttheestimator,(78),(86).

Havingestimatedforeachtime-seriesthetrendthroughtheLMStechnique,weexaminewhethertheresidualsfollowaparticularpattern.Thepresenceofapatternintime-seriesresidualsusuallyindicatesthatthederivedmodelhasnotabsorbedallthecharacteristicsofthetime-series.Itwasoftenobservedthatresidualspresentacorrelationamongthem,afactwhichleadstousethosethatdocorrelatewitheachother,soastolessentheresidualerrorandthereforeachieveforecastswithagreaterprecision.

LMSapproachisappliedwiththeuseoftheso-called“Singularspectrumanalysis(SSA)”technique.TheSSAtechniqueisusedtoreconstructprincipalcomponentsofthetime-seriesandputsasideinconsequentialcharacteristics.

Fig.4.7.Thepercentageofoutliersforwhichvariousstatisticalmethodsbreakdown,(78),(86)

AnexampleofanactualapplicationoftheLMSmethodinrailwayproblemscanbegivenbytakingintoaccountdataofyearlydemandillustratedinFigure4.3.ApplicationofLMSandSSAmethodsgivesresultsillustratedinFigure4.8.,(78).

Fig.4.8.ForecastofdemandwiththeuseofLMS-SSAmethods,(78)

4.9.Statisticalevaluationoftheforecastingabilityofamodel

TheforecastingabilityofamodelaswellasacomparisonamongmanymodelsdescribingaphenomenonistestedwiththeU–Theilstatisticsmethod,(74).

WhentheU–Theilstatisticsofamodeliscalculatedequaltozero,thenthemodel’sforecastingabilityisperfect,whereaswhentheU–Theilstatisticsiscalculatedequaltoone,themodellacksanyforecastingability.TrustworthyforecastscanbeconcludedwhenthevalueoftheU-Theilstatisticsrangesfrom0to0.30,(74),(77).

Acomparisonhasbeenconductedtoevaluatetheforecastingabilityoftheeconometricandfuzzymodels,givenbyequations(4.6)and(4.10)respectively,andtheLMSmethod,whichallthreedescribethesamephenomenon.TheU-Theilstatisticstakesthevalueof0.244fortheeconometricmodel,0.253forthefuzzymodeland0.258fortheLMSmodel.Thusthemodelwhichbestdescribesthephenomenonunderstudyistheeconometricone.

Anothermethodofevaluatingtheforecastingabilityofvariousmodelsisthecalculationofthesquarerootofthemeansquareerror(RMSE),(74).ThemodelwiththesmallestvalueofRMSEaffordsthebestaccuracyofforecast.

Figure4.9givesthecomparativeperformanceofthevariousmodels(Econometric,Fuzzy,LMS)andcomparisonwithrealdata.

Fig.4.9.Comparativeperformanceofvariousmodelsofraildemandforecast,(77)

4.10.Acomparativeanalysisofperformancesofeachmethod

Thequestionarisingconcernsthechoiceofthemostappropriatemethod;

however,theanswerdependsonthefollowing,(Table4.4):Natureandrangeoftheforecast:Forshort-(1÷2years)andmedium-(<5years)termforecasts,Statisticalprojectioncanbeafirstandrathersuitablemethod.TheresultsoftheStatisticalprojectioncanbecomplementedbyandcorrelatedwiththeDelphimethodoranExecutivejudgment.Iftheforecasterwantstonormalizeunpredictableeventsconcerningpastdata,thenbesidestheStatisticalprojection,hecantrytheLMSmethod.Yet,long-term(>5years)forecastswillrequireacausaltechnique,usuallyanEconometricmodel.Besidesusualregressionanalyses,theforecastercanuseapplicationsoftheFuzzymethodinordertodetermineamoreaccuraterangefortheforecastandrelievetheforecastfromtheimpactofunusualeventsinthepast.

Table4.4.Acomparativeanalysisofperformancesofthevariousforecastingmethods

ofraildemand

Incaseofanewlineoranewstation,aMarketsurvey,whichistime-consumingandcostly,isnecessaryandmustbecomplementedbyaGravitymodel.

–Expertiserequired.Executivejudgment,Delphimethod,Scenariowriting,Econometric,GravityandFuzzymethodsrequireaqualifiedforecasterwithahighlevelofexpertise,whileStatisticalprojectionsandMarketsurveyscanbe

conductedbylessqualifiedpersonnel.–Timeavailable.Foraforecastwithinsomehoursordays,aStatisticalprojectionaccompanied,ifpossible,byanExecutivejudgmentorDelphimethodistheonlyaccurateapproach.Iftheforecasterhastimeavailableforthecompletionofhisforecast,regardlessofthecost,hecantrymoretime-consumingmethods,suchasanEconometricmodel,aMarketsurvey,etc.

–Dataavailability.Statisticalprojectionsandcausalmodelsrequireaccuratedataforaratherlongperiodoftime.Ifsuchdataareunavailableorunreliable,thentheuseofqualitativemethodsissuggested.

–Costoftheforecast.EconometricmodelsandMarketsurveysarecostlymethods,comparedtoStatisticalorQualitativemethods.Finally,anyforecast,mostparticularlyamedium-orlong-termone,should

becheckedandupdatedwithnewdata.However,thelongertheperiodofforecastthelessertheaccuracythatcanbe

expected.Forecastsformorethan10yearsaheadshouldbeusedonlyasanindicationofwhatmayoccur.Forecastswithintherangeof5÷10yearshaveaninherentuncertainty,ofwhichtheforecastershouldbeawareof.

4.11.Modellingofrailfreightdemand

RailfreightdemandDijfrompointitopointjcangenerallybeexpressedbythefollowingfunction,(22):

where:Oi :Productionofproductinpointi,

Pi :Demandofproductinpointj,

Cij :Generalizedcostforfreighttransport,

b: Parameterofcalibration.

GeneralizedcostCijinfreighttransportisexpressedas,(16):

where:fij :fareforfreighttransportfromoriginpointitodestinationpointj,

Sij :totaltraveltimefromoriginpointitodestinationpointj,(transshipmentincluded),

σSij :varianceoftotaltraveltime,

Wij :waitingtimefromthemomentdemandhasbeenmanifestedtillthebeginningofthetransportationprocedure,

Pij :probabilityoflosses,alterationofproducts,robberies,etc.

InaneconometricmodelfortheforecastofrailfreightdemandinCanada,alogarithmicformbetweenthedependentvariable(railfreight)andtheindependentvariableshasbeensuggested.Theindependentvariableswere:volumeandvalueofcommoditiestransportedbyrail,railfreighttimes,freightrevenue,andthenumberofroadvehicles,(94).

*ForexamplethesoftwareMicrosoftExcel,Grapher,Microfit,EviewsandHarvardGraphicsare,amongothers,suitedforthispurpose.

*Fortwopairsofstatisticaldata(xi,yi),(xj,yj),theslopeisdefinedas:(yj-yi)/(xj-xi),andtheinterceptisdefinedas:yi-slope·xi

5CostsandPricing

5.1.Definitionofrailwaycosts

5.1.1.Constructionandoperationcosts

Understandingthestructureofrailwaycostsisessentialandcrucialforallrailwayactivities.Constructionofanewrailwaylinewillbestronglybasedonanaccurateknowledgeofcosts.Operationofarailwayservicealsoneedsthemostaccurateanddetailedknowledgeofcosts.Pricingofinfrastructurerequiresknowingthevaluesofmaintenancecosts.Establishingtariffsforpassengerandfreighttrafficrequiresknowledgeofbothoperationcostsandelasticities.

Costcanbedefinedastheamountofavailableresourcesspentinconjunctionwiththeconstructionoroperationofarailwayactivity,(116).Railwaycostscanrefereithertotheconstructionofaline,inwhichcasetheyarecalledconstructioncosts,ortotheoperationofarailwayservice(passenger,freight,combined,terminal),inwhichcasetheyarecalledoperationcosts.

Whenaseparationofinfrastructurefromoperationexists,wealsodistinguishtheinfrastructurecost,whichisthesumoftrackcostsrelatedtotheprovisionanduseofatrack.Thesecostsincludemaintenanceandoperationcostspertainingtosubgrade,ballast,sleepers,rails,signaling,telecommunications,electrictractioninstallations,lighting,policeinspection,aswellastostationinstallationsandthestaffneededtooperatetheinfrastructure,(116).

5.1.2.Fixedandvariablecosts

Fixedcostsrefertothosecostswhichdonotvarywiththeleveloftraffic.Incontrast,variablecostsrelatetothequantityoftraffictransported.Totalcostsarethesumoffixedandvariablecosts.

5.1.3.Marginalcost

Marginalcostistheadditionalcostwhenincreasingtrafficbyoneunit.Morestrictly,marginalcostisdefinedastheunitcostresultingfromanincreaseordecreaseintrafficvolume(progressiveorregressivemarginalcost).Whenthevariationintrafficisinfinitelysmall,thisquotientisthederivativeofcostinrelationtotraffic,(112).

Marginalcostmayrefereithertoagivenproductioncapacity(short-termmarginalcost),ortoachangingproductioncapacity(long-termmarginalcost),whichusuallyneedsalongerperiodtooccur.

Developmentcostisthetotalofallcostsincurredtoimplementanewrailfacilityorproject(e.g.newrollingstock,station,line,etc.)

ThecostsofarailwayactivityinrelationtotrafficcanbeillustratedasinFigure5.1.Wecandistinguishthefollowingcomponentsofcosts,(115):

Fig.5.1.Totalcostsinrelationtotrafficforanewrailwayline

a.fixedcosts(sectionOAofthecurve),relatedtotheexpensesofadministration,maintenance,etc.,

b.fixedcosts,relatedtoaspecificcategoryoftraffic.Ifforinstanceinalinerunbypassengerandfreighttrains,passengertrainsareeliminated,thentheadditionalcomponentofmaintenancecostsrelatedtopassengertrafficwilldisappear,

c.marginalcosts(sectionBCofthecurve),relatedtofuel,maintenanceofrollingstockandnecessarypersonnelinthetrains.Railwaysarecharacterizedbythefactthattrafficusuallydoesnotreachcapacityandthusrailway

infrastructureisinmostcasesunderutilized,d.developmentcosts(sectionDEofthecurve),relatedtothepurchaseofnewrollingstock,ortheconstructionofanewlineorfacilityinordertorespondtoademandthatcannotbeconfrontedwiththeexistinginfrastructureorrollingstock.

5.1.4.Externalcostsandmarginalsocialcost

Externalcostsarethecoststhattheuseofatransportsystemimposesonnon-usersofthesystem.

Marginalsocialcostofinfrastructureisdefinedasthetotalcostentailedbytherunningofanadditionaltrainonaparticularinfrastructureandiscomposedof,(116):i.amarginalcostrelatedtoinfrastructure,whichmeasurestheincreasein

maintenanceandrenewalcostsresultingfromanadditionaltrainrunning,ii.amarginalcongestioncost,expressinginmonetarytermsthevalueofdelays

andconstraintsimposedontherestofthetrafficbyanadditionaltrainrunning,

iii.amarginalexternalcost,representingtheincreaseinothercoststothesocietyincurredbytherunningofanadditionaltrain.Thiscostmeasuresprincipallythevariationofcostsofaccidents,pollution(airandsound),climatechange,etc.

5.1.5.Generalizedcost

Aperson’schoicebetweentwomodesoftransportationismadebytakingintoaccountthreeparameters,(16),(107):thedirectmonetarycost,whichinthecaseofrailwaysisthesumofthetrainticketcostplusthecosttoreachthedeparturestationplusthecostfromthearrivalstationtothedestinationpoint,(Fig.5.2),thevalueoftotaltraveltimeh(fromorigintodestination),thequalityofserviceq.

Fig.5.2.Directcostfromorigintodestinationpoint

Thegeneralizedcost(GC)takesintoaccounttheabovethreeparametersandisdefinedasthesumofthedirectmonetarycost(DMC)paidbythetravelerplusthemonetaryvalueoftotaltraveltimeplusthemonetaryvalueofqualityofservice:

where:h:thetimefromorigintodestination,T:themonetaryvalueofaman-hour,(seealsosection22.7).Whenrailwaysincreasespeedandreducetraveltimes,thenforaspecific

valueofman-hour,thegeneralizedcostisreducedandsometrafficcandivertfromairplanes,busesandprivatecarstotherailways,(Fig.5.3).

Ontheotherhand,reducedrailtraveltimesmayleadtoincreasedrailrevenues.Indeed,passengerswithahighvalueoftime(e.g.businessmen)maybewillingtopayahigherrailtariff,ifrailtraveltimesaresubstantiallyreduced(comparedtocompetingmodes)andleadtolowergeneralizedcosts.

Fig.5.3.Divertedtrafficwhenreducinggeneralizedcost

5.2.Constructioncostofanewrailwayline

5.2.1.Factorsaffectingrailconstructioncost

Theconstructioncostofanewrailwaylineisinfluencedbyseveralfactors:layoutcharacteristics,mainlythenumberandsizeofbridgesandtunnels.Itshouldbenotedthatinrailwaylinesofcomparablelevelsofservice,theexistenceofmanycivilengineeringstructures(tunnels,bridges)maydoubleoreventripletheconstructioncost,expropriationcost,which,especiallyinurbanareas,mayconsiderablyincreaseconstructioncosts,

costsrelatedtoworksnecessaryfortheprotectionoftheenvironment,numberperkilometerofswitchesandcrossings,numberofelectricalsubstations,laborcosts,whichvaryfromcountrytocountry(andoftenwithinthesamecountry).

Theuseofcostdatabasedoninformationfromtheanalysisofothercountriesshouldthereforeserveonlyasaroughestimateofthevariouscostparameters,alwayskeepingproportionsinmind.

5.2.2.Constructioncostsfornewhigh-speedlines

Costdatafromlinesforhighspeedsconstructedduringrecentyearscangiveafirstestimationoftheconstructioncostofanewhigh-speedrailwayline.

Thenewhigh-speedline‘TGVMéditerranée’ofFrenchrailways,inoperationsince2001,withVmax=350km/h,onballast,with6.5%oftunnelsand12.7%ofbridges(reportedtothetotallengthoftheline),hadaconstructioncostperkmof17.75million€(allmonetaryvaluesarethatofyear2008*).

TheSpanishhigh-speedlineMadrid-Barcelona,inoperationsince2003,withVmax=270÷350km/h,onballast,hasinthepartwith26.8%oftunnelsand3.4%ofbridgesaconstructioncostperkmof6.40million€.Inthepartwithfewertunnelsandbridges(with2.0%oftunnelsand2.7%ofbridges),constructioncostperkmisreducedto3.35million€.

TheGermanhigh-speedlineCologne-FrankfurtwithVmax=300km/h,onconcreteslab,with26.5%oftunnelsand4.2%ofbridges(reportedtothetotallengthofline)hasaconstructioncostperkmof22.7million€.

TheItalianhigh-speedlineRome-NapleswithVmax=300km/h,onballast,with17.8%oftunnelsand24.0%ofbridgesperkmofline,hasaconstructioncostperkmof20.5million€.

ThenewKoreanhigh-speedline,withVmax=300km/h,onconcreteslabintunnels(across-sectionof107m2)withalengthgreaterthan5km,onballastelsewhere,hasaconstructioncostperkm(including46unitsofhigh-speedrollingstock)of44.6million€.

Table5.1recapitulatestheabovecostdata.Railwayengineers,managersandeconomistsshouldthereforebeverycarefulwhentryingtoassesstheconstructioncostsofanewrailwayline.

Table5.1.

Constructioncosts(valuesofyear2008)ofhigh-speedlinesconstructedduringrecentyears(compiledfromdataofUICandconstructors)

5.2.3.Allocationofcoststothevariousrailcomponents

Theallocationofconstructioncostsofanewrailwaylinetothevariouscomponentsoftherailwaysystemdiffersgreatlyanddependsonthepeculiaritiesofeachparticularsituation.Figure5.4illustratestheaveragevaluesfromdataofFrance,Spain,Germany,Italyforlineswithnomajorcivilengineeringstructures.

Fig.5.4.Allocationofconstructioncostsofanewrailwaylinetothevariouscomponentsoftherailwaysystem(compiledfromfielddata)

5.2.4.Constructioncostsofcivilengineeringworks

Basedonalargenumberofcasestudies,acompletelistoftheconstructioncosts

ofcivilengineeringworks(subgrade,expropriations,tunnels,bridges)ofnewtracksinrelationtospeed,difficultyoftopography,singleordoubletrackisgiveninTable5.2,(110).ThevaluesinTable5.2arefortheyear2008andforeachcaseanaverageormedianvaluewiththeloweranduppervaluearegiven.Asstatedinparagraph5.2.1,valuesofTable5.2shouldbeconsideredasordersofmagnitudeandreferencepoints.

Table5.2.Constructioncostsofcivilengineeringworks(valuesofyear2008)ofanew

railwaylineinrelationtospeedanddifficultyoftopography,(110)

Incaseofdifficulttopography,theconstructioncostisincreasedduetothenumberoftunnelsandbridgesthatwillbenecessary.Medianvaluesfortheexcavationofatunnelareforadoubletrack36.6million€/kmandfortheconstructionofabridgeorviaductare18.3÷36.6million€/km,dependingonthelengthofthestructure,theheight,thefoundation,(110).

5.2.5.Constructioncostsoftrack

Constructioncostsoftrack(rails,sleepers,ballast)amountto0.37÷0.61million€/km,(110).

5.2.6.Constructioncostsofelectrictraction

Electrictraction(seechapter20)costsinclude,(110):•substationscosts:0.24÷0.37million€/km•catenarycosts:0.18÷0.24million€/km

5.2.7.Constructioncostsofsignaling

Railwaysignalingsystems(seechapter21)costsinclude,(110):

–cables(forsignalingandcommunications):0.06÷0.12million€/km,–automaticblocksystem:0.18÷0.37/blocksection,–automaticoradvancedtrainprotection:0.024÷0.037million€/unit,–cabsignal(automatictraincontrolwithtransmissionbytrackcircuitsorbycables):0.37million€/blocksection,

–radiolinks:0.024÷0.050/km,–levelcrossings.Theircostdependsonwhethertheyareequippedwithautomatichalfbarriers(0.37million€/unit),fourautomaticbarriers(0.85million€/unit),oraresimplyequippedwithlightandacousticsignals(0.037million€/unit).

5.3.Maintenanceandoperationcostsofinfrastructure

5.3.1.Maintenancecostofinfrastructure

Whetherintegratedorseparated,itisessentialtoknowthemaintenanceandoperationcostsofinfrastructure.Infrastructuremaintenancecostscomprises:maintenanceandrenewaloftrack(rails,sleepers,ballast)andsubgrade,maintenanceofelectrification,signalingandtelecommunicationsfacilitiesandsubstations,maintenanceoftunnelsandbridges,maintenanceofplatforms(instations).

Amaintenancecostperyearof47,000€/kmoftrackwasreportedforFranceandacostof60,000€/kmwasreportedfortheNetherlands(monetaryvaluesfortheyear2008).Thiscostisallocatedasfollowstothevariousmaintenancecomponents:–65%fortrackandplatforms,–30%forelectrification,signaling,telecommunicationsandsubstations,–5%forbridgesandtunnels.

5.3.2.Operationcostofinfrastructure

Theoperationcostsofinfrastructureincludetrafficmanagement(92%oftotaloperationcosts)andscheduleplanning(8%oftotaloperationcosts),andareestimatedperyearat1.35€/train-km(valuesofyear2008).

5.4.Costofpurchaseofrollingstock

5.4.1.Costofhigh-speedrollingstock

Asthereisavarietyofcontractsforthepurchaseofrollingstock,significantdifferencescanbeobservedamongtheprincipalrollingstockconstructors.

Thecostperplaceforthepurchaseofnewrollingstock(valuesfortheyear2008)is75,100€fortheSpanishhigh-speedtrain(namedAVE),64,750€fortheGermanICE1and73,650€forICE2,67,500€fortheParis–Brussels–Amsterdam–Colognetrain(namedThalys),and46,600€÷48,700€fortheFrenchhigh-speedtrains.

Ifwereportthepurchasecostperseat-kmandperyear,thenwehavethefollowingvalues:0.221€fortheSpanishAVE,0.130€fortheGermanICE1and0.184€forICE2,0.225€forThalys,and0.116€÷0.123€fortheFrenchTGV,(Table5.3).

Astheairplaneistheprincipalcompetitorofhigh-speedtrains,acomparisonwiththeeconomicdataconcerningaircraftmaybeuseful.Thus,thecostperseatis386,000€forBoeing757-200(withacapacityof190seats),550,000€forBoeing767-200ER(withacapacityof191seats)and362,000€forAirbusA320(withacapacityof150seats),(valuesfortheyear2008).Costsreportedperseat-kmandperyearare0.167€forBoeing757-200,0.177€forBoeing767-200and0.217€forAirbusA320.Itcanbededucedthathigh-speedtrainsandairplaneshavecomparablepurchasecostsperseat-kmandperyear,(Table5.3).

Table5.3.Costofpurchaseofhigh-speedrollingstockandofaircrafts(valuesofyear

2008),(compiledfromdataofUICandconstructors)

5.4.2.Costofordinarypassengervehicles

Thecostofordinarypassengervehiclesisreportedtobe1.60÷1.95million€/vehicle,(110).

5.4.3.Costoffreightvehicles

Thecostoffreightvehiclesdependsonthecharacteristicsofthevehicle(open-covered,flat-hopper,etc.)andaverages80÷100.000€/vehicle,(110).

5.4.4.Costofdiesellocomotives

Thecostsofdiesellocomotivesarespreadoveragreatrangeofvalues.AsaroughapproximationtheymaybecalculatedinrelationtothepowerW(inMW)ofthelocomotivefromtheempiricalformula,(110):

costofadiesellocomotive(inmillion€)=W/3+1

5.4.5.Costofelectriclocomotives

Similarly,thecostofanelectriclocomotivecanbecalculatedfromtheempiricalformula,(110):

costofanelectriclocomotive(inmillion€)=2W+2.

5.5.Economiclifeofthevariouscomponentsoftherailwaysystem

Thevariouscomponentsoftherailwaysystemcanbeusedefficientlyandsafelyforamoreorlesslimitedperiodoftime,whichiscalledeconomiclife(andsometimesservicelifeorusefullife),whichdependsonthenature,degradationandscopeofthespecificcomponent.Thus,inadditiontothevariouscomponentsofcostanalyzedpreviously,itisessentialtoknowhowmuchtimeafreightvehicleorarailoranotherrailwaycomponentmaybeusedandwhenitshouldbereplaced.

Theeconomiclifeofarailwaycomponentisdefinedastheperiod(usuallyexpressedinyears)duringwhichthespecificcomponentisexpectedtobeusable,withnormalrepairandmaintenance,(16).Economiclifeisusuallylessthanphysicallife,whichisthetimeuntilthemomentthatfurtheruseofarailwaycomponentmaybedangerousandsafetyisnotassured.Thedepreciationperiodmaycoincidewiththeeconomiclifebutduetovariousuncertaintiesmaywellbelowerthantheeconomiclife.Anyrailwaymaterialorcomponentshould

bereplacedbeforetheendofitseconomiclife.Theeconomiclifeofarailwaymaterialorcomponentdependsonthe

economicconditionsofthecountryandtherailwaysandmaydiffergreatlyfromonecountrytoanother.AveragevaluesofeconomiclifeofthevariousrailwaycomponentsandmaterialsfortheeconomicconditionsofEuropearegiveninTable5.4,(16),(110).

Table5.4.Economiclife(inyears)ofvariouscomponentsandmaterialsoftherailway

system,(16),(110)

5.6.Costofoperationofarailwaycompany

5.6.1.Passengertransport

Costsdiffergreatlyinthevariouscategoriesofrailpassengertraffic:urbanandsuburban,intercity,regional.Statisticsofrailoperatorsusuallyrefertothewholeactivityandlackanalyticaldata,whichtheyshouldhaveforeveryspecificcategoryoftrafficandevenmoreforeveryroute.Railwaysshouldintroduceanalyticalaccountingtechniquesinordertohavethepossibilityofanaccurate

measureofcostsforeverysegmentofthemarketandforeveryroute.Thegreatvarietyofcostsisreflectedatavarietyofrevenuesperpassenger-

kilometer.Somevaluesforfourrailwaysoperatingindifferentpartsoftheworld(dataofyear2008)aregiveninTable5.5,(106).

Table5.5.Averagerevenues(in€)perpassenger-kilometerforvariousrailway

operators,(106)

ThefourrailwayoperatorsofTable5.5,despiteoperatingindifferentcontinentsandwithindifferentmarkets,havemuchincommon.Thesimilarfeaturesarethefollowing:alargenon-concentratedcustomerbase,awelldiversifiedrevenuemix,thedirectorindirectgovernmentsupport,andhighbarriersforcompetitorstoentertomarket.TheJapaneseoperatoristheonlyprivatizedone.

5.6.2.Freighttransport

Costoftransportisasmallcomponentofthetotalvalueoffreight.Formediumandlongdistances,transportcostsrepresentapproximately21%ofthevalueoffreight,(102).Thismeansthatonlyhighreductionsinthetransportcostcanhaveanessentialeffectonthetotalcostofthegoodstransported.Forthisreason,reliabilityandontimedeliveryareessentialfactorsintheverycompetitivefreighttransportmarket,(102),(113).

Asexplainedinsection1.9,railwayspresentcomparativeadvantagesformediumandlongdistances.Accordingtothestatisticsforthe15countriesoftheEuropeanUnion,(Table5.4),49.1%oftotalton-kmsoffreightareperformedbyrailfordistancesfrom150to500kms,9.3%fordistancesfrom50to150kms,only2.4%fordistancesshorterthan50kms,andtheremaining39.2%fordistancesgreaterthan500kms,(109).

Weusuallydistinguishfixedfromvariablecosts.Rollingstockandstaffrepresentfixedcosts,whereasaccesschargesandenergyconsumptionrepresentvariablecosts.

Manyrailwaycompanieschoosenottopublishdataconcerningfreightcosts.Wewillpresentananalysisoffreightcosts,whichreferstothelaborcostsofItaly.Tables5.5and5.6presenttheoperationcostsofafreighttrainofausefulloadof315tand630trespectively.

5.6.3.Combinedtransport

Thecostofcombinedtransportdiffersinrelationtototaldistance,partialdistancestraveledbyrailandroad,theterminalequipment,etc.,andithasbeenillustratedinFigure1.21(section1.9.3).

Table5.6.Shareinfreighttransport,inrelationtodistance,ofvarioustransport

modesforthe15EUcountries,(109)

Table5.7.Costofoperationofrailfreightforatrainwithausefulloadof315t(values

ofyear2008),(109)

Table5.8.Costofoperationofrailfreightforatrainwithausefulloadof630t(values

ofyear2008),(109)

5.7.Quantificationofexternaleffectsinmonetaryvalues

Formanydecades,acrucialissueconcerningthevariouscomponentsofexternaleffectswastheiraccurateandobjectivequantificationinmonetaryvalues.Thisworkhasbeenconductedandappliedtodataoftheyear2008,andreferstothe25EUcountries(MaltaandCyprusdonothaverailways)plusNorwayandSwitzerland,(95).

Thevariouscomponentsofexternalcostsare:accidents,noise,airpollution,climatechange,natureandlandscape,additionalcostsinurbanareas(separationandspacescarcity),up-anddown-streamprocesses,andcongestion.AllthesecomponentshavebeenidentifiedanddescribedascanbeseeninTable5.9.Foreachoneofthemanappropriatemethodforquantificationinmonetaryvalueshasbeendeveloped,(Table5.9).Congestioncostsareusuallypresentedseparately.Other(non-costrelated)aspectsofexternalcostsarepresentedinChapter22.

Table5.9.Descriptionofthevariouscomponentsofexternalcostsandmethodsof

theirquantificationinmonetaryvalues,(95)

Totalexternalcosts(excludingcongestioncosts)amountfortheyear2008tomorethan500billion€,whichis4.0%oftheGDPofthe27countriestakenintoaccount(25EUcountries+Norway+Switzerland).Climatechangeisthemostimportantcostcategory,with29%ofthetotalcosts.Airpollutionamountsto10.4%andaccidentcostsamountto43%ofthetotalcosts.Thecostsofnoiseandup-anddown-streamprocessesamountto9.6%oftotalcosts.Thecostsfornature,landscapeandundesiredurbaneffectsamountto1.0%oftotalcosts,

(95).Roadtransportisthemodewiththehighestshare(93%)intotalexternal

costs,followedbyairtransport(5%).Itshouldbestressedthatinthecalculationofexternalcostsofairtransport,(95),onlyflightswithinEUhavebeentakenintoaccount,somethingthatexplainsthelowshare(5%)ofairtransportintotalexternalcosts.Onthecontrary,railwayshaveasmallshare(lessthan2%)intotalexternalcostsandwaterwaysevensmaller(0.3%).Twothirdsofexternalcostsarecausedbypassengertransportandonethirdbyfreighttransport,(95).

Figures5.5and5.6illustratetheaveragevaluesofthevariouscomponentsofexternalcostsforalltransportmodes,forpassengerandfreightrespectively,(95).Table5.10illustratesvaluesofmarginalexternalcostforpassengerandfreightrailtransport,(105).

Manyeffortstointernalizeexternalcosts(thatistoexpecteachtransportmodetopaytheexternalcostsitcauses)havefailedtobeapprovedaslegislation.Amongthevariousscenariosofinternalization,themostefficientoneshouldbefuelpricing,whichtakesintoaccountallexternaleffectsforeachtransportmode,(114).

Fig.5.5.Averageexternalcostsforpassengertransportforthevarioustransportmodes,(25EUcountries+Norway+Switzerland),(95)

Fig.5.6.Averageexternalcostsforfreighttransportforthevarioustransportmodes(25EUcountries+Norway+Switzerland),(95)

Table5.10.Externalcostsofrailpassengerandfreighttransport,(105)

5.8.Pricingofinfrastructure

5.8.1.Principlesofinfrastructurepricing

Pricingofinfrastructure(whichmeanschargesforoperators)musthavethefollowingcharacteristics:simple,transparent,stable,fair,non-discriminatory,andefficient.Inaddition,itshouldtakeintoaccount:–theessentialcharacteristicsofthespecificinfrastructure(speed,availabilityofdepartureandarrivalslots,electrification,signaling),

–traincharacteristics(length,axleload,permittedpower,etc.),–efficientuseofinfrastructureandconsistencywithgeneraltransportpolicyobjectives.

Pricingofinfrastructureisgenerallybasedontrain-kilometer.

5.8.2.Objectivesofinfrastructurepricing

Anyinfrastructurepricingmodelshouldclearlyestablishitsobjectivesandrankthembypriority,(20),(96):•cover,inwholeorinpart,theoperatingandmaintenancecostsofrailways.

Table5.11recapitulatesthevariousassetsandcostsofinfrastructure.Ifinfrastructureaccountisnotbalanced,thenapublicsubsidyisnecessarytocoverthedeficit,

•favorthebestpossibleuseofrailinfrastructure,•promotesomecategoriesoftraffic(urban,regional,intercity,freight),•reflectthelevelofservicesprovidedtotherailoperator,•takeintoaccountexternaleffectsandthuscompensatetransportmodes(likerailways)whicharemorefriendlytotheenvironment,

•contributetothecostsofdevelopingtherailnetworkthroughmakinginvestmentself-financing,

•contributetoabalancedregionaldevelopment.

Ascertainoftheaboveprinciplesarecontradictorytosomeextent,theinfrastructurepricingmodelshouldestablishacompromiseandaddresstherankingofpriorities,whichshouldbecharacterizedbycohesion.

5.8.3.Financialconsequencesofinfrastructurepricing

Infrastructurechargescanbehigh,whichisbeneficialforpublicfinancesanddetrimentaltothefinancesofrailwayoperatorsrunningonthespecificinfrastructure.

Ontheotherhand,ifinfrastructurechargesarelow,thisisbeneficialforrailwayoperatorsbutdetrimentaltopublicfinances.

Table5.11.Railinfrastructureassetsandcosts,(112)

5.8.4.Acommercialapproachofinfrastructurepricing

Railinfrastructurecanbeconsideredeitherasacommercialproduct(thatis,aproducttosell)orpartofthepublicestate(thatis,apublicutility).Eveninthesecondcase,however,thepricingofrailinfrastructureshouldbecharacterizedbyacommercialapproach,whichmeans:–flexibilityofprices(without,however,anydiscrimination),–thepossibilityofdiscountforrailoperatorswithheavytraffic,–allocationprocedures,whenmanyrailoperatorsareseekingforthesamedepartureorarrivalslot.

Figure5.7illustratestheparameters,whichcouldbetakenintoaccountinapricingmodel,(108).

Fig.5.7.Factorsaffectingapricingmodelofrailinfrastructure

5.8.5.Theoreticalandpracticalinfrastructurepricing

Therearemanytheoreticalalternatives,eachoneofwhichleadstopricingaccordingtoacomponentofinfrastructurecost,whichmaybe:marginalcost(short-term),marginalsocialcost,includingexternalities,marginalsocialcostofinvestment(long-term),includingthecostofrenewalinvestment,totalcost.

Economictheorysuggeststhatoptimalpricingshouldbebasedonthelong-termmarginalsocialcostordevelopmentcost,(114).Somecountries(e.g.Germany,UnitedKingdom)combinetheprincipleofcoverageoftotalcostswiththefinancialpotentialoftherailwayundertakings.Thus,thestatesubsidizesthetheoreticallyhighchargesthattherailoperatorsareunabletopay.

Pricinginsomecountriesisbasedonthemarginalsocialcost,whereasinothercountriesonlyonmarginalcost.Inbothcases,thesemethodsresultindeficitsthatarecoveredbystatesubsidies.

5.8.6.Structureofinfrastructurepricing

Wecandistinguishtwogreatstructuresofinfrastructurepricingmodels:•one-partmodels,withasinglecomponentbasedonvariablecostandweightingfactors:speed,axleload,equipmentoftrack,electrification,specific

route,timeofday(slot),typeofcommodity,etc.•two-partmodels,withonecomponentbasedonvariablecostandanotherfixedpart,whichcanreflectcapacitytobeusedandpathallocation,withouthoweveranydiscrimination.

5.9.Infrastructurepricingmodelsinsomecountries

5.9.1.InfrastructurepricingaccordingtoEuropeanUnionlegislation

EuropeanUnionprinciplesforpricingrailinfrastructurecanbesummarizedasfollows,(20),(60):–Overareasonabletimeperiod,theaccountsoftheinfrastructuremanagershallbalancerevenuesfrominfrastructurecharges,commercialactivities,andstatesubsidieswithinfrastructureexpenditures.Chargesshouldbepaidtotheinfrastructuremanagerinordertofundhisbusiness.Chargesmustbenon-discriminatoryfordifferentrailwayundertakingsthatperformservicesofanequivalentnature.Chargescannotbesmallerthanmarginalcosts.

–Anydiscountshallbelimitedtotheactualsavingoftheadministrativecostincasesoflong-termcontracts.Limiteddiscountscanbegrantedtoencouragedevelopmentofnewrailservicesortheuseofunderutilizedlines.Forsimilarservices,similardiscountschemesshallbeapplied.

–Acomponentofpricesmaybereservationchargesasanincentiveforanefficientuseofcapacityandshouldreflectthatcapacity,which,ifrequested,shouldbepaidevenifnotused.

–Chargesmaytakeintoaccountthefollowingparameters:distance,natureoftraffic,compositionoftrain,speed,axleload,timeofuseofrailinfrastructure(slot),electrificationandsignalinginstallations,whetherornotinfrastructureisunderutilized,etc.

TheinformationoninfrastructurechargesgiveninthefollowingparagraphsistakenfromtheNetworkStatementofeachInfrastructureManagerofEU(dataofspring2013).ThoughtheNetworkStatementisanobligationforallInfrastructureManagers,theEuropeanCommissionhasnotdictatedanystandardformatfortheNetworkStatement.Thus,theinformationgivendiffersfromonecasetoanother,inspiteofthefactthat33InfrastructureManagersinEurope(including25EUcountriesplusNorway,Switzerland,Croatia,etc.)havepromulgatedacommonformatfortheNetworkStatement.

5.9.2.France

TheFrenchpricingmodelofrailinfrastructuretakesintoaccountthefollowingcategoriesoflines:•suburbanlines(withheavyandmediumtraffic),•mainintercitylines(withheavyandmediumtraffic),•high-speedlines,•otherlines.

Railinfrastructurechargesarecomposedofthefollowingcomponents:accesscharge,paidpermonthandperkilometeroflineforwhichaccessisrequested.Itissimilartothefixedchargefortheuseofacreditcard,reservationcharge,perkilometerandperslotreserved.Itispaidevenifthereservationrequestediscancelled.Thelevelofreservationchargeisarelationofthefrequencyofuseofthespecificlineorslot,operatingcharge,pertrain-kilometer,calculatedinrelationtodistance,qualityoftrack,departuretime,etc.chargefortheuseofelectrictraction,calculatedpertrain-kilometer,specialcharges(fortheuseofcombinedtransport,marshallingyards,etc.).

Chargesaredifferentiatedforpeakperiods(06.30÷09.00and17.00÷20.00),normalperiods(04.30÷06.30,09.00÷17.00,20.00÷00.30)andslackperiods(00.30÷04.30).

5.9.3.Germany

TheGermanpricingmodelisarelationofthefollowingparameters:qualityofinfrastructure(maximumspeed,locationoftheline,technicalandgeometricalcharacteristics,electrification,signaling,automaticregulationinlevelcrossings).Theentirenetworkissubdividedintotwelvelinetypes,composedofseventypesoflongdistancelines,twotypesofso-calledfeederlinesandthreetypesofrapidtransitpassengerlines,(108),trafficcategory.Thenetworkisdividedintothreecategories,inrelationtothenature,characteristicsandrequirementsoftraffic.Foreachtrafficcategory,routepricesdifferandtakeintoaccounttheabilityofoperatorstopay,loadfactorandrequirementsconcerningpunctualityanddeteriorationoftrackinrelationtothenatureoftraffic.TheGermanpricingmodelhastwocomponents:

–acomponentforthepurchaseofanetworkcard(aflatrateforayear),which

isbasedonthenumberofline-kilometers.Thecardpermitstheuseofthenetworkcategorypurchasedandonthelinescontainedwithinit,

–acomponentrelatedtothenumberoftrain-kilometerstraveled.

Ifarailoperatorperformsonlyafewtrain-kilometers,hemustpaytheso-calledvariablecharge,whichisafunctionofthetrain-kilometers,therespectivenetworkcategoryandtheloadfactoroftheline.

Networkcardpurchasersmayobtainatimediscountiftheypurchaseacardeveryyearforaperiodoftenyears.

Thus,railinfrastructurechargesCarecalculatedinGermanyaccordingtotheformula:

wherea:basecharge,inrelationtotrafficcategoryandutilization,b:productfactorrelatedtotrackparameters,c:surchargesorreductionsforspecialtrains,d:surchargesorreductionsforweightclasses,tiltingtrains,etc.,e:factorofregionalityofline.

Itistooutlinethatfinalvaluesofchargesarefarlowerthanbasecharges.

5.9.4.UnitedKingdom

TheBritishrailchargingsystemaimsfirstlyatatrafficincreaseandsecondarilyatthecoverageofcosts.Ithastwocomponents,afixedoneandavariableone,(101).

5.9.5.SwedenandFinland

Thepricingmodelisbasedonmarginalsocialcostandhasthefollowingcomponents:–circulationcharge,whichisdifferentforpassengerandfreight,–chargeforaccesstostations,–environmentalandaccidentscharge.

5.9.6.Italy

TheItalianpricingmodelhasthefollowingcomponents:–useofinfrastructure,whichiscalculatedbytakingintoaccounttrainspeed,departuretime,compositionoftrain,densityofcirculation,

–accesstostations,whichisnullforregionalstations.

Reductionsareaffordedforlowspeeds,circulationinnon-peakhours,highvolumesoftraffic,etc.

5.9.7.Switzerland

TheSwissmodelhasafixedpartandavariablepart,thesecondonebeingafunctionofthefinancialpotentialofrailoperators.

5.9.8.Othercountries

Pricingmodelsinothercountriestakeintoaccountparticularitiesandspecificcharacteristicsineachcase.Forinstance:–Denmarkhasacomponentforaccessinbridges,–AustriaandBelgium(bothhavingahighdensityoftraffic)haveacomponentconcerningthedensityoftrafficandcongestion.

Table5.12summarizesthecharacteristicsofrailaccesschargesystemsforthevariousEuropeancountries.

5.9.9.Acomparisonofrailinfrastructurecharges

RailinfrastructurechargesinEuropepresentgreatdifferencesfromonecountrytoanotherandreflectstatepoliciesandinterventions,usuallyinordertoprotectthehistoricalstate-ownedrailoperator.

Forinstance,intheUnitedKingdom,charges,whicharedifferentfromonerailoperatortoanother,canbeconsideredhigh,buttheyaregreatlysubsidizedbythestate.

InSwitzerland,theoreticalchargesforfreighttrafficarealsohigh,butalmosttwothirdsofthesechargesarecompensatedforbystatesubsidies.

Highdifferencescanbeobservedbetweenchargesforpassengerandfreighttrains.Somecountries(e.g.Poland)havehigherunitchargesforfreighttrains,other(e.g.France,UnitedKingdom,etc.)havehigherunitchargesforpassengertrains,whilesomecountries(e.g.Sweden,Portugal,etc.)haveasimilarlevelofunitcharges,bothforpassengerandfreighttrains.

Inconclusion,concerningrailpricingmodels,twogreatcategoriescanbeobserved:–modelsbasedonshort-runmarginalcost(UnitedKingdom,Switzerland,Sweden,Norway,TheNetherlands)withorwithoutexternalities,

–modelsbasedonlong-runmarginalcost(France,Germany,Italy).

Thetendency,however,isforchargestoreflectasmuchaspossibletherealcostofmaintenanceandoperationofinfrastructure,aswellasarealequityforalloperators,whichmeansthatthecriticalcomponentsofchargesshouldbevariablecosts(relatedtothetraveleddistances),whereascomponentsoffixedcostsshouldbegreatlyreduced.

Table5.12.CharacteristicsofaccesschargesystemsforthevariousEuropeancountries,

(99)

OutsideEurope,thereisalsoagreatrangeofinfrastructurecharges,whichreflectdifferentobjectivesofcostrecovery,differentbalancesbetween

passengerandfreight,networkcomplexitiesandtheintensitiesoftraffic.Figures5.8,5.9,5.10illustrateinfrastructurechargesinEuropeforpassenger

trainsandFigures5.11,5.12forfreighttrains(allvaluesofyear2008).Figure5.13illustratesthepercentageofvariablecostsofinfrastructurerecoveredfrominfrastructurechargesforvariousEuropeancountries.

Fig.5.8.Infrastructurecharges(€/train-km)fortypicallocalandsuburbantrainsforvariousEuropeancountries,(99)

Fig.5.9.Infrastructurecharges(€/train-km)forintercitypassengertrainsforvariousEuropeancountries,(99)

Fig.5.10.Infrastructurecharges(€/train-km)forhigh-speedtrainsforvariousEuropeancountries,(99)

Fig.5.11.Infrastructurecharges(€/train-km)foratypical960tonfreighttrainforvariousEuropeancountries,(99)

Fig.5.12.Infrastructurecharges(€/train-km)foratypical2,000tonfreighttrainforvariousEuropeancountries,(99)

Fig.5.13.PercentageofvariablecostsrecoveredfrominfrastructurechargesforvariousEuropeancountries,(99)

5.10.Pricingofoperation

5.10.1.Targetsofpricingofoperation

Thepricingofoperation(whichleadstotariffsforpassengersandfreight)shouldcovertheexpensesoftherailoperator,whileatthesametimeassuring

thefinancingofthenecessaryinvestmentforrenewalandmodernizationofitsequipment(rollingstock,etc.).Tariffisdefinedasthechargepaidbytheuserofarailservice.Tariffsaimat:partortotalcoverageofexpenses,orientingclientstothoseserviceswhicharemorebeneficialeitherfortherailoperatororforthesociety.

Arationalpricingshouldtakeintoaccountexistingorofferedcapacity,cost,demandforecasts,priceelasticityofdemandandcrosselasticities(seesection5.10.3)withcompetingmodes.

5.10.2.Thetraditionalmethodofpricing

CostC(x)ofrailtransportisusuallyexpressedasasumoftwocomponents(equation5.3):one(B·x)dependingonthedistancetraveled(x)andtheother(A)beingconstantforeachspecificrouteandrepresentingexpenseswhicharenotarelationofthevolumeoftraffic,

Basedonthisstructureofcost,railcompanieshaveusedformanydecadesasimilarformulaforpricing:

Variablebisnotconstant,butusuallyisdifferentiatedinrelationtotherangeofdistanceitrefersto.

5.10.3.Effectsofelasticities

Priceelasticityofdemandhelpstoassesstheextenttowhichdemandisaffectedasaresultofachangeinpriceandisdefinedas:

where:ep:priceelasticityofdemand,q:demandwhenpriceispΔq:changeindemandwhenthepricechangesfromptop±Δp.

Priceelasticitymayrefertoshort-termorlong-termchanges.Itisarelation

ofdistance,thepurposeoftripandthespecificconditionsforeachcase(existenceandfaresofcompetingmodes,etc.).Asaroughestimate,railpassengerpriceelasticitiescanbegivenvaluesaround–0.6,(112).

Whenpriceelasticityisclosetozero,thenanincreaseintariffsof1%hasnoeffectindemandandconsequentlyisbeneficialfortherailoperator.Thiscanbeencounteredinsomeurbanorsuburbanrailservices.

Whenpriceelasticityisbetween0and–1,anincreaseintariffsof1%willcauseareductionindemandtoapercentagelessthan1%andanincreaseinrevenuesbetween0and1%.Theglobaleffectofsuchastrategymayormaynotbebeneficialfortherailoperator.

Whenpriceelasticityequals–1,thenanincreaseintariffsof1%causesareductionofdemandof1%andthusrevenuesremaininvariable.

Whenpriceelasticityislessthan–1,anincreaseintariffsof1%causesareductionofdemandofmorethan–1%andthusrevenueswillbereduced.

Incomeelasticityreflectshowachangeinrealincomeaffectsdemandandisdefinedas:

where:ein:incomeelasticity,Ι:realincome,ΔΙ:changeinrealincome.

Railincomeelasticitiesaregivenmediumvaluesaround+0.8witharangefrom+0.50to+1.50,(112).

Cross-elasticityofdemandmeasureshowthedemandforonetransportmodechanges,whenthepriceofanothermode(competitororsubstitute)changes,andisdefinedas:

where:ei,j:thecrosselasticityofdemandfortransportmodei(e.g.,rail)inrelationtoachangeinthepriceofmodej(e.g.,privatecar),

qi :thedemandoftransportmodeiwhenitspriceispiandthepriceoftransportmodejispj,

Δqi :thechangeinthedemandoftransportmodeiwhenthepriceoftransportmodejchangesfrompjtopj±Δpj.

CrosselasticityofraildemandwithrespecttothecostofuseofprivatecarhasinWesternEuropevaluesaround+0.20÷0.25,(112).

5.10.4.Pricingandcompetition

Traditionalmethodsofpricingbasedondistance(andgivenbyformula(5.4)ofsection5.10.2)arenotcurrentlyanefficienttoolforpricing,sincetheyignorecompetitioninthetransportmarket,whichcomeseitherfromothermodes(road,air)orisintra-modalcompetitioncomingfromotherrailoperatorsrunningonthesameinfrastructure.

However,thechoicesofclientstouseaspecifictransportservicearebasedontwocriticalparameters,tariffandqualityofservices(whichisarelationoftraveltimes,comfort,justintimearrival,etc.).Evidencehasshownthatifclientsaresatisfiedwiththequalityofservices,thenamoderateincreaseintariffsmayhavepracticallynoimpactindemand,(15),(75).AccordingtoasurveyinKoreain2004,includingbothbusinessandleisuretravelers,decisionfactorsandtheirdegreeofimportancewhenconsideringlong-distancetravelwereasfollows:fare:32.8%,safety:22.5%,accessibility:18.5%,traveltime:15.3%,comfort:6.8%,frequency:4.1%,(103).

Competitionputspressureonrailoperatorstotakeintoaccounttariffsappliedbytheircompetitorsandthustoabolishthetraditionalpricingmethodbasedondistance.

5.11.Pricingofpassengertraffic

5.11.1.Theexistence(ornot)ofpublicserviceobligations

Asexplainedinsection3.2.3,publicserviceobligationsaretheserailservicesthat,iftheonlyconsiderationoftherailwayswerebusinessprofit,wouldnothavebeenundertakentothesameextentordegree(e.g.theoperationoflineswithsmalltraffic,lowtariffsforsomesegmentsofthemarket,etc.).

Publicserviceobligationscanrefereithertocertaincategoriesoftraffic(theelderly,students,etc.)ortotheregionserved(isolatedornon-accessibleareas).

Inbothcases,theauthorityimposingapublicserviceobligationmustsubsidizethelostrevenuesoftherailoperator.Thejustificationforpublicserviceobligationsliesontheoriesofregionalityandonthefactthateverycitizenshouldhaveaminimumlevelofaccessibility,whichisassuredbymorethanonetransportmodes.

Publicserviceobligationsaim(atleasttheoretically)atmaximizationofthepublicbenefit;theyusuallyrefertopassengertransportandonlyrarelytofreighttransport.

5.11.2.Thestrategicdilemma:profitorincreaseoftraffic

Thedecisionatthedilemmaofchoosingbetweenprofitandincreaseoftrafficistheresponsibilityofthestatepolicyandoftherailoperator.

PricingstrategiesaimingatprofithavebeenadoptedintheUnitedKingdomandGermany,amongothers,andhaveledtotheabandonmentofmanysecondarylines.Surprisinglyandinspiteofhighunittariffs,thisstrategyhasledtoanincreaseoftrafficintheUnitedKingdomandelsewhere.

Pricingstrategiesaimingatanincreaseoftraffichavebeenadoptedinmanycountrieswithaninterventionistpolicy,amongtheminFrancewhereunittariffsarehalfcomparedtothoseofGermanyandfavormoresocioeconomicfactorsandlessentrepreneurialspirit.Inmanycases,however,thispolicyleadstodeficits,whicharecoveredbystatesubsidies.Inanycase,aprerequisiteforthesuccessofthisstrategyisahighqualityofrailservices;otherwisesuchastrategymaybecatastrophic.

5.11.3.Pricingforrailoperatorswithoutpublicserviceobligations

Railoperatorswithoutpublicserviceobligationsareobligedtobalancerevenuesandexpenses.Tariffsshouldnotbelessthanmarginalcostsandcanbeashighasthemarketcanbear.

Forsimilarlevelsofqualityofservice,railtariffsshouldnotexceedareferencevalue,whichisdefinedbytariffsofcompetingmodes.Bysettingatargetforthetrafficoftherailoperatorandtakingintoaccounttariffsofcompetingmodes,econometricmodelscanfacilitatethecalculationofrailtariffstobeapplied.

SuchastrategyhasbeenusedbyEurostar,where,forasimilarqualityofservice,railtariffsarelowerby15%comparedtotariffsoftheprincipalcompetitor,whichistheairplane.

5.11.4.Yieldmanagementtechniques

Theeverydayproblemofarailoperatoristomakethemaximumprofitofthecapacityoffered,whichifnotusedislost.YieldManagementtechniqueshavebeenusedbyairlinessoastocombinethebestuseofthecapacityofferedwithamaximizationofprofits.

Yieldmanagementreliesontheso-calledRamseypricingtechnique,whichsuggeststhatthesoonertheticketisbought,thehighertheofferedreductionintariffswillbe.Forinstance,Frenchrailwaysofferareductionupto50%forTGVticketsboughttwomonthsbeforetheactualdateoftravel.Germanrailwaysoffera40%reductionintariffsforticketspurchased7daysbeforetheactualdateoftravel,a25%reductionfora3dayadvancepurchase,a10%reductionforapurchasejustonedaybeforetheactualdateoftravel.

Yieldmanagementprinciplesleadtoadifferentiationoftariffsandcantakeintoaccountthefollowingcharacteristics:periodoftheday,byofferinglowertariffsinnon-peakhours,dayoftheweekandseasonoftheyear,soastodiscourageanextensiveuseduringweek-endsorholidayperiods.

Thedifferentiationoftariffsleadstoamaximizationofrevenues,permitsapenetrationtoothersegmentsofthemarket,andcanhave(atleastapparently)thecharacterofasocialpolicy.However,ithasalsonegativeeffects.Forthoseclientswhopaidahighertariff,thereistheriskofdisappointment,whichisoffsetbyofferingthemotherbenefits,suchassupplementaryservices,deliveryofluggage,etc.

5.11.5.Complementarycommercialmeasurestoincreaserevenues

Commercialpolicyofarailoperatorisbasedonmarketing,advertisingandtariffpolicy.Commercialmeasuresaimat,(16):segmentsofthemarket,likestudents,theyoung,tourists,theelderly(morethan60or65yearsold),pensioners,personnelofenterprises,travelofgroups,foreigners,strengtheningthelinkbetweentherailoperatoranditsclients,byimplementingmeasureslike:–cards(daily,monthly,yearly)offeringunlimiteduseonrailservicesfortheownersofthespecificcard,

–advantagesandfreeticketsforclientswhoarefrequentusersofrailservices.

5.12.Pricingoffreighttraffic

Pricingoffreighttrafficmusttakeintoaccountfaresofroadtransportandrailcosts.Railfreightinmostcountriesdoesnothaveanykindofpublicserviceobligationsandthusrevenuesshouldcovertotalcosts(analyzedpreviouslyinsection5.6.2).

However,railfreighttariffscannotberaised,unlessrailwaysgetridofvarioushandicapsrelatedtorailfreighttraffic,(15):•lowrailshipmentspeed,whichforEuropehasamediumvalueof18km/h,againstamediumshipmentspeedofaround50km/hforroadfreight,

•punctuality,whichisforrailwaysfarawayfromthelevelof95%ofroadfreight(deliveryofgoodsintheagreedtime,withamarginofamaximumdelayof60minutes),

•quasi-impossibilityforrailwaystoachievedoor-to-doorrailfreighttransport.

Mostofthesehandicapsarearesultofco-existenceonthesametrackoffast(passenger)trainsandslow(freight)trains,thelatterusuallybeinggivenalowerpriority.ThishandicapdoesnotappearintheUSA,whererailwaysarespecializedinfreighttraffic,butisfrequentinEuropeandAsia.Asaremedy,ithasbeensuggestedtotransformsomerailrouteswithheavyrailtraffictodedicatedfreightcorridors,onwhichfreighttrainswillruneitherexclusivelyorwithpriority.Dedicatedfreightcorridorsaretheequivalentforfreightoflinesdedicatedonlytohigh-speedtraffic.Technicalspecificationsforsuchdedicatedrailfreightcorridorscouldinclude,(15):•amaximumspeedof100÷120km/h,theprincipaltargetbeingtoachieveamediumrailshipmentspeedapproaching50km/h.Highspeedsmaybejustifiedonlyfortrafficofproductswithahighvalue,

•anaxleloadof22.5tons(seesection7.5),•alengthofplatformsfrom600mto750m,allowingtherunningoflongfreighttrains,

•aloadinggaugeintunnelscompatiblewiththeloadinggaugeGCofUIC(seesection7.10),

•asignalingofthetypeofversion3ofERTMS(seesection21.9.4),•electrificationsystemsthatcouldfeedmulti-currentlocomotives,•appropriateequipmentinmarshallingyardsinordertominimizelongdelaysinthetransferofgoods,

•facilitiesofcombinedtransportandparticularlyequipmentforthehorizontalloadingofcontainers,

•sidingswithclientswhogeneratehighrailfreightflows.

*Mostofthecostspresentedinthischapterareexpressedinmonetaryvaluesoftheyear2008.Duetotheeconomiccrisisafter2008,particularlyinEurope,someconstructorstriedtogainmarketsharebydumpingprices,whilemanyrailwayauthoritieshadtocutdrasticallycosts.Thus,updatestothemonetaryvaluesoftheyear2013wouldhaveriskedingivinganon-representativeimageofcostsintherailmarket.

6PlanningandManagementofRailways

6.1.Railwaysandthesocialandeconomicenvironment

6.1.1.Asystemsapproachfortherailways

Consideredeitherasawholeorseparated(infrastructure-operation),railwaysconstituteacomplexsystem.Eachcomponent(track,traction,operation)hasmanysub-components(e.g.fortrack:rails,sleepers,etc.),theinteractionofwhichisnoteasytopredict.However,agoodsynergyofallrailcomponentsisnecessaryinordertoachievethedesirableresult,i.e.safe,quick,comfortableandlowcosttransportofpeopleandgoods.Forthisreason,railwaysshouldalwaysbeexaminedasasystem.

ApplicationofsystemsapproachinrailwaysisgiveninthesimplifiedflowchartofFigure6.1.Eveniftheproblemfocusesonatechnicalneed,railwaymanagersshouldbeginfromdefiningtherealproblem,whichcouldbeputas:‘Whatisthetransportneedtobesatisfiedandwhatarethetargetsbeingaimedat?’.Ineverystepofasystemsapproach,allalternativesolutionsshouldbecarefullyexamined.

6.1.2.Railwaysandthesocialandeconomicenvironment

6.1.2.1.Thesocialandeconomicenvironment

Eachrailwayactivitymustbeexaminedinrelationtoitsinternalandexternalenvironment,(Fig.6.2).Thewholeorganizationofrailwaysmustbecharacterizedbytheprincipleofadaptability,thatistheabilitytoadapttochangingsituationsofitsinternalandexternalenvironment,(122).

6.1.2.2.Strategicandtacticallevelofdecisions

Inmanagement,weoftendistinguishbetweenthestrategicandthetacticalororganizationallevelofdecisions.Tobemorespecific:

Fig.6.1.Systemsapproachappliedinrailwayproblems

Fig.6.2.Railwaysandtheirinternalandexternalenvironment

•thestrategiclevelofdecisionsreferstothefundamentalorientationsoftherailwayundertaking,suchas:revenues/expensesratio,volumeofpassengerorfreighttraffic,levelofstatesubsidies,etc,

•thetacticalororganizationallevelofdecisionsconcernsthefollowing:introductionofnewtechnologies,changesinhumanresources,organizationalchanges,etc.

Theadaptabilityoftherailwayactivitytoitsenvironmentrequiresthefollowingstepsoftacticallevel,(36):–periodic(e.g.all3or6months)comparisonbetweentargetsandachievedresults(e.g.volumeoftrafficorrevenues,etc.),

–localizationofdivergences,researchofreasonsandformulationofthepossiblemethodstoconfrontthedivergences(e.g.inthecaseoflossoftraffic,newmethodsofmarketing,modificationoftheproductoffered,newpersonnel,etc.),

–choiceandapplicationofthemostappropriatemethod,–followingoftheevolutionaftertheintroductionofthenewmethod(e.g.whatistherateofincreaseoftrafficorrevenuesaftertheintroductionofthenew

method),–ifdivergencespersist,thismeansthattacticalororganizationalmeasuresarenotsufficientanddecisionsatstrategiclevelshouldbeundertaken,suchasclosureorendingofanactivity(forinstance,freighttransportoflowtraffic,passengerservicesbetweenlowdensitypopulationareas),creationofanewservice,etc.

6.1.2.3.Separationinbusinessunits

Asrailwayactivityisextremelycomplexandiscomposedofmanyactivitiesthatusuallybearnorelevancetoeachother(e.g.activitiesofmarketingandtrackmaintenance),itismandatorytoseparateandcategorizeactivitiesinseparatehomogeneousunitsthatarecalledbusinessunits.Atypicalcategorizationofthewholerailwayactivityinbusinessunitsis:

infrastructure(maintenanceandoperation),rollingstock(maintenanceandoperation),operationofpassengertraffic,operationoffreighttraffic.

Someoftheabovebusinessunitsmayfurtherbedividedinsmallerones,thusrollingstockcanbedividedintwounits:onebeinginchargeofmaintenanceandtheotherinchargeofoperation.

6.1.2.4.Changesandrequirementsoftheenvironmentofrailways

Theseconddecadeofthe21stcenturyischaracterizedbyafastchangingenvironmentwiththefollowingfacts,(15):•theeconomiccrisissince2008inmanypartsoftheworldandthedebtcrisisinEuroperequirerailwaystodrasticallyreducecosts,increaserevenuesandfaceefficientlybothinter-modalandintramodalcompetition,

•economyandsocietychangequickly(atleastconcerningappearancesandexigencies)andaskfornewproductsandservices(e.g.justintimedeliveryoffreight,increasedqualityofservice,etc.),

•researchanddevelopmentofnewtechnologiesmayquicklyrenderexistingtechnologiesobsoleteandwithoutanyvalue(e.g.electronicticketing,ifintroducedinrailways,dramaticallychangestheexistingticketingsystems),

•continuouschangesandnewproductsofcompetitors(e.g.low-costairtransport)hasobligedrailwaystodrasticallychangetheirofferandtariffsinmanyroutes,

•changesinthepolicyofgovernmentandworldinstitutionsconcerningsocial

security,fullliberalization,consumerprotection,pollution,humanrights,etc.(e.g.railwaysinthecaseofgreatdelaysmustcompensateclients)imposeabruptchangesinstrategyandorganization,

•frequentandfastchangesinthevaluesofthesocietyandthepeople(concerningsafety,environmentaleffects,etc.)putpressureonrailwaystoincreasesafety,somethingthatresultsinadditionalcosts,

•conditionsofsurvivalinsuchachangingenvironmentaretheuseofsystematicmarketing,inordertomonitorintimeforthcomingchangesandadjustproductsandpolicyoftherailwaystotheexternalrequirements.

6.1.3.Qualitycontrol

Verificationofachievementofgoalscannotbelefttoanempiricalassessment,aswasthecaseinthepast.Criteriaofassessmentshouldbeclearandquantifiable.Qualitycontrolaimstoassureconsistencywithcertainstandardsandwiththeneedsofcustomersinmind.Qualitycontrolisusuallyeasierforproductsthanforservices(suchasrailservices).QualitycontrolisofgreatimportanceandrailwaysmustadopttheISO(InternationalStandardsOrganization)orsomeothercertification.Since2006,railwayshavetheirownISO,theISO9001.Inaddition,theEuropeannormEN13816(‘QualityandQualityManagementinPublicTransportServices’)prescribesmethodsandprocedurestoassurequalitycontrolandachieveanhomogeneous(intimeandspace)railproduct.Figure6.3illustratesanexampleofhowrailwayorganizationandefficiencycanbeimprovedthroughrationalsuccessivestepsandwithcontinuousqualitycontrol.

Fig.6.3.Organizationandcontroloftherailwayactivity,(126)

6.2.Competitionandimpactonrailwaymanagement

Railwayshaveoperatedformanydecadesasaphysicalmonopolyundertheprotectionistumbrellaofthestate,whichcoveredallthedeficitsthattherailwayactivitywasproducing.Thisbecomeslessandlessthecasewitheachpassingyear.Competitionisincreasingandcanbeeitherexternal(i.e.inter-modalcompetitionfromothertransportmodes)orinternal(i.e.intramodalcompetitionamongmanyrailoperatorsrunningonthesametrack).

However,whilecompetitionisincreasing,regulationstillholds.Infact,throughregulation,governmentsubsidizesrailwaydeficits,setsandimposestariffs,definesregimesofentry-licensing-accessfornewrailwayoperatorsanddemandsincreasedlevelsofsafety.

Thestructureoftherailwayshasdirecteffectsonmanagement.Whetherseparatedorunified,itgreatlyaffectsthemethodsofmanagementtobeapplied.

Inastronglycompetitivemarket,railwaysshouldtry:–tohavethelowestgeneralizedcostinordertoattractnewclients,–tounderstandandtakeintoaccountallkindsofelasticities(i.e.price,revenue,cross)inordertoreactintimebeforelosingmarkets,

–topresentanewimageofthespecificrailwayactivity,

–toestablishacloserandpermanentlinkamongclientsandthevariousrailwayactivities.

Fig.6.4.Effectsofcompetition,regulationandstructureonthemanagementoftherailways,(99)

6.3.Feasibilitystudiesandmethodsoffinancing

6.3.1.Needforevaluationofanyrailproject

Inthepast,somerailwaylineswereconstructedaspartofanationaldevelopmentplan,orforstrategicandsecurityreasons,orforthedevelopmentofnationalresources,withoutdetailedeconomicorfinancialconsideration.Astimeschange,oldpracticesarenolongervalid.Evenasmallrailwayprojectmustbejustifiedfromaneconomicandfinancialpointofview.Clearandcompleteanswersshouldbegivenfromtheearlystagestoquestionssuchas:“Whyisthisrailwaylineorfacilityneeded?”,“Whatdowewantittoachieve?”.Otherwise,thereistheriskofconstructingarailinfrastructure,whichwillcreatedeficits,andwillhavelowtraffic,whilethemoneyspentforitcouldhavebeenusedforothermoreusefulandefficientpurposes.

6.3.2.Benefitsandcostsfromnewrailwayinfrastructure

Feasibilitystudiescomparebenefitstocostsofthespecificrailwayproject.Costhastwobasiccomponents:

–constructioncost,–operationcost.

Benefitsfromtherealizationofarailwayprojectcanbe,(16):•reductionoftraveltime,•reductionofoperationcost,•reductionofaccidents,•improvementofthequalityofservice,•regionalandnationaldevelopment,•securityandnationalintegration.

Amongtheabovebenefitstheonlydirectandcommercialoneisthereductionofoperationcosts,whereasallotherbenefitsarerelatedtosocialreasons.Comparisonofbenefitsandcostsimpliesthatallbenefitsshouldbetransposedinmonetaryterms.Thisinvolves:–Fortraveltimes,anassessmentofthevalueoftime.Manyrailwayprojectshaveasaprimaryobjectivethereductionoftraveltimes.Reducedtraveltimesarethemainbenefitwhenconsideringarailprojectandaccountusuallyfor2/3oftotalbenefits.However,whatisthemonetaryvalueofaman-hoursaved?Thereisnodoubtthatthevalueoftimeisdifferentforabusinessman,apublicservant,astudent,apensioneroranunemployedperson.Eachcategoryoftraffichasitsdifferentvalueoftime.Extremelygreatdifferencesconcerningvaluesoftimeexistfromonecountrytoanother,(seesection22.7),(118).

Savedtraveltimesrelatedtoworkactivitiesaretakenintoaccount100%infeasibilitystudies.Savedtraveltimesrelatedtoleisure,tourism,etc.aretakenintoaccountatapercentageof20%÷35%,(129).

–Forregionalandnationaldevelopment,assessmentoftheincreaseofeconomicproductintheconsideredregionorcountry,

–Foraccidents,evaluationinmonetarytermsinthecaseofadeathoraninjury.

6.3.3.Evaluationmethodsforrailprojects

Therearemanyevaluationmethodsforrailprojects,(16),(129):InthemethodofPresentValue(PV),allexpenses(forconstructionandoperation)arecalculatedfortheentireeconomiclifeoftheproject;thealternativesolutionwiththelowestpresentvalueisthemosteconomicone.InthemethodofNetPresentValue,foreachalternativethenetpresentvalueiscalculated,accordingtothefollowingformula:

NPV=(B–O)–(C–Y)(6.1)

where:

NPV:NetPresentValue,B:Presentvalueofallbenefits,O:Presentvalueofalloperationcosts,C:Presentvalueofconstructioncosts,Y:Salvagevalue(theproject’svalueattheendofitseconomiclife).

IntheCost-Benefitmethod,theratioλiscalculatedasfollows:

Aprojectistoberealizedifλ>1.Amongmanyalternativesolutions,theonewiththegreatestvalueofλischosen,(120).IntheInternalRateofReturn(IRR)method,thevalueofthediscountrateiscalculated(bythetrialanderrorprocedure),forwhichthepresentvalueofbenefitsequalsthepresentvalueofexpenses.IfIRRisgreaterthantheopportunitycostofcapital,thenthespecificrailprojecthaschancestoberealized,(129).Previousmethodsofevaluationfocusoneconomicparameters,sincetheyassessutilitycausedbyarailproject.Inthisway,however,importantparameterssuchasqualityofservice,mobility,noisepollution,etc.,areneglectedintheevaluationprocedure.Multi-criteriamethodshelptotakeintoaccountallparametersrelatedtoarailproject:constructioncost,operationcost,expecteddemand,reductionoftraveltimes,increaseinnationalorregionalproduct,qualityofservice,safetyandsecurity,landuse,airandnoisepollution,mobilityandaccessibility.Eachparameterisgivenaweightfactor,whichreflectsprioritiesofevaluation.If,forinstance,constructioncostisgivenahighweightfactor(sayof50%),thiswillleadprobablytotheselectionofalowcostsolution.If,incontrast,expecteddemandisgivenahighweightfactor,thiswillleadtoaprojectservingmorepeople,(124).

However,itshouldbestressedthattheselectionoftherailprojecttoberealizedislargelyapoliticaldecision.Evaluationmethodsjusthelptorationalizetheprocedureofselectingaparticularproject.

6.3.4.Methodsoffinancinganewrailproject

Theeconomicrealityisthatmostofthefinancingoftheprivatesectorisorientedtowardindustrialprojects(particularlyintheenergysector)withonlyasmallparttotransportprojectsandevenasmalleroneforrailprojects.Principalreasonsforthissituationarethehighcostofrailandtransportprojects,thelong

periodofconstruction(3÷7years)andtherelativelylowexpectedrevenues.AsillustratedinFigure6.5,thecashflowofarailprojectbecomespositiveonlywithin15÷20yearsfromthebeginningoffinancing,alongperiodforbankersandentrepreneurs.Incontrast,thecashflowofanindustrialprojectbecomespositivewithin5÷6yearsfromitsbeginning,(128).

Fig.6.5.Cashflowofarailwayandofanindustrialproject,(128)

Railprojects,inthemajorityofcases,areanunattractiveinvestmentfortheprivatesector.Forthisreason,theyaremostlyfinancedbystatefundsandthenoperatedasapubliccompany.However,theworldwideeconomicenvironmentexercisespressureonpublicfinancesandreducesthepossibilitiesforstatestofinanceunprofitablerailprojects.Forthisreason,moreandmorerailmanagersareaddressedtotheprivatesectorforthefinancing(partialortotal)ofsomeoftherequiredinvestment,clearlythemostattractivefromarevenuegeneratingpointofview.

Inthecaseoffinancingarailprojectthereareseveralcriticalissues:•firstofall,whogivesthemoney,thestateortheprivatesector,(i.e.,banks,entrepreneurs)?

•whoundertakestheriskduringconstruction?Forinstance,iftheinitiallycalculatedconstructioncostwereincreasedby30%,whowouldpaythisadditionalmoneyneeded?

•whentheprojectisfinished,whowillruntheoperation,therailwaycompanyorthecompanywhichconstructedtheproject?Asrailwayprojectsareextremelycomplex,constructorsareusuallyunwillingtooperatetheprojectstheyhaveconstructed,

•iftheconstructorofarailprojectalsoundertakesitsoperation,whoisinchargeofentrepreneurialrisksduringtheoperation?Forinstance,ifrealdemandwereby25%lessthantheforecasteddemand,whowouldpaythe

difference?

6.3.5.Public-PrivatePartnerships

Dependingontheanswertothequestionsraisedinprevioussections,therearemanyschemesofinvolvementoftheprivatesectoratthefinancingofarailproject,knownasPublic–PrivatePartnerships(PPPs),(121):–intheBuild–Operate–Transfer(BOT)method,aprivatecompanyundertakesinapublicbidding,understatespecifications,arailproject,finances(partiallyortotally)itsconstructionandthenoperatesitforaperiod,usually20÷40years,butevenupto99years(ChannelTunnel).Duringtheconcessionperiodtheowneroftheprojectisthepublic(i.e.theinfrastructuremanagerortheoperator).Returnoftheinvestedmoneyisachievedthroughrevenuesfrompassenger,freightorcommercialactivities.AvariationoftheBOTmethodistheBuild–Own–Operate–Transfer

(BOOT)method,inwhichtheprivatepartnerownstheprojectduringitsoperation.AvariationoftheBOOTmethodistheBuild–Own–Lease–Transfer(BOLT)method,inwhichtheprivatepartnerleases,afterconstruction,thefinishedprojecttotherailauthority,whichpaystotheprivatepartnerperiodicpaymentsfortheinvestedcapital.

AnothervariationoftheBOTmethodistheBuild–Transfer–Operate(BTO)method,inwhichuponcompletionofitsconstructionbytheprivatepartner,therailcompany(infrastructuremanageroroperator)becomestheowneroftheprojectandrentsitforaperiodtotheprivatesector.

IntheBuild–Own–Operate(BOO)method,theprivatepartnerfinances,builds,ownsandoperatestheprojectforaperiodduringwhichhecanearnrevenuesfromtheoperationoftheproject.Themethodissuitableforinvestmentsinrailwaystations,wherefacilitiesmayservemanyusers.–InthePrivateServicesContract:OperationsandManagement,theinfrastructuremanagerconcludesforaspecificfacilityacontractwithaprivatepartner,whoisinchargeofitsoperationandmaintenance,whiletheinfrastructuremanagercontinuestobetheownerandinchargeofmanagement.AvariationofthismethodisthePrivateServicesContract:Operation,

MaintenanceandManagement,inwhichtheprivatepartnerisalsoinchargeofthemanagement.–IntheDeveloperFinancingmethod,anareabelongingtotherailwaysisgiventoaprivatepartnerwhoconstructsarailfacilityandinreturnthepartneris

giventherighttoconstructhouses,commercialcentersorindustrialfacilities.Themethodissuitableforareaswithahighvalueofland.

–IntheLong-TermLease,railfacilitiesareleasedtoaprivatepartnerwhoinvestsmoneyfortheirmodernizationandthenoperatesthemforaspecificperiod.AvariationofthismethodistheLease–Rehabilitate–Operatemethod.Selectionofthemostappropriatemethodisdoneinrelationtothe

characteristicsoftherailproject(e.g.,anewtrack,anewstation,amarshallingyard,upgradingofafacility,etc.),theexpecteddemandandrevenues,therisksduringconstructionandoperation,etc.

6.4.Planningtherailwayactivity

6.4.1.Needandpurposesofplanning

Humanactivityisdevelopedinanextremelycomplexenvironment.Whenthisactivityconcernsacomplicatedsystem,likearailway,thentheneedemergesforallcomponentsofthesystemtobeconstructedandoperatedinordertoachievethebestresult.Organizationandinvestmentshouldcontributetothisresult.Apowerfultooltoachievefixedtargetsisplanningandisunderstoodastheprocessthatsetsgoals,definesactionstobeperformed,estimatesandallocatesresources,determinesstagesintimeanddeadlines,identifiesresponsibilitiesforactionsanddefinesmechanismsofmonitoringandevaluation,(130).

Aplanningproceduredepartsfromunderstandingtheexistingsituation,triestoforecastplausibleevolutionsinthefuture,anticipatescomingproblemsandevolutions,suggeststheinvestmentandorganizationthatwillberequiredandlooksforthenecessaryfundstofinancethesuggestedactions.

Therearemanylevelsofplanning,inrelationtotime:–long-termplanning,whichreferstothecoming10÷15yearsanddescribesthewholeorsectorialstrategies,whereinvestmentshouldbeorientedandthefinancialstrategytobefollowed,

–medium-termplanning,whichreferstothecoming3÷5yearsandisanimplementationofthelong-termplanningatmediumlevelconcerningstrategy,detailedinvestment,organizationalchangesandfunding,staffrequirements,commercialandtariffpolicies,

–yearlyplanning,whichisdetailedintheyearlybudgetoftherailwayactivity.

Itisclearthatamongthevariouslevelsofplanning,thereshouldbeaconsistencyofgoalsandmeasures.Forinstance,adecisiontolowertariffsand

increasetrafficmaybebeneficialintheshortterm,butmaybenegativeinthemediumorlongterm,ifthereisnoavailabilityofrollingstocktoserveincreaseddemand.

Planningisnothingmorebutthemanagementofchange;failureoftherailwaystorespondtimelyandefficientlytoexternalchangesmaybedisastrous.

Railwayplanningisaframework,withinwhichthevariousfacilitiescanoperatetheirseparatefunctionsatthehighestpossiblelevelsofefficiency.Successfulplanningmustbecharacterizedbyflexibilityandadaptability.

6.4.2.MasterPlansandBusinessPlans

MasterPlansandBusinessPlansarethemostcurrentformsofplanningrailwayactivity.MasterPlansrefertothewholeoftherailwayactivityandcontainanalysisofinvestment,technicalequipment,organizationandfinance.However,BusinessPlansemphasizeonorganizational,economicandfinancialaspects.EachinfrastructuremanagermusthavehisMasterPlanandeachrailwayoperatorhisBusinessPlan.

AMasterorBusinessPlancanbedefinedastheconceptionofaplannerforthefurtherdevelopmentofthevariouscomponentsandoperationsofarailwaysystem.Itistheframewithinwhichtheplannersuggeststheevolutionanddevelopmentofthevariouscomponentsoftherailwaysystem,i.e.higherefficiency,productivityandrevenues,whilereducingcostsandrespectingenvironmentalrules.

AMasterPlanisnotanimplementationprogram,assomebelieve,butaguideandnothingmore.Itisbasedoncertainassumptionsconcerningtheevolutionoftheeconomy(suchasGrossDomesticProduct,consumerprices,etc.)andofthetransportmarket(shareofeachmode,prices,elasticities)anditsuggestsscenariosforconfrontingfutureevolutions.AMasterPlanshouldbeupdated,ifpossible,onayearlybasis.AMasterPlanmustclearlysettargets,prioritiesandmethodsofimplementation.

IfinaMasterPlan,technicalaspectsandproblemsaregivenlesspriority,thenwehaveaBusinessPlan.

Wheneveranewinvestmentorexpenseissuggestedinplanning,thecrucialquestion‘whopaysthebill?’shouldbeclearlyanswered.

6.4.3.AbriefdescriptionofaBusinessPlanofarailwayundertaking

BusinessPlansvaryconsiderablyfromonecountrytoanother,duetotheinfluenceofdiversehistorical,geographical,sociological,demographicaland

economicfactors.However,allrailBusinessPlansshouldcontainaminimumofanalysisdescribedbelow(15),(130):

a)Externalsocio-economicenvironment:economicgrowth,agricultural,industrialandeconomicproduction,tourism,populationanddemography,legislation,statepolicy.

b)Railwaysandthetransportmarket:evolutionofrailways’shareandtraffic,tendenciesofthetransportmarket,situationandprospectsofcompetingmodes,forecastsforfuturerailwaytraffic.

c)Financialsituation,costsandproductivity:Evolutionofrailrevenuesandexpenses,costsandtariffs,comparisonwithcostsandtariffsofcompetingmodes,yieldanalysis,personnelemployedandunitcostsofservices,productivityindices(totalandsectorial),comparisonwithotherrailways.

d)Weaknessesofpresentorganizationandmanagement.e)Formulationofanewstrategyandtargets,thatshouldbequantifiable,suchasanewexpenses/revenuesratio,increaseoftrafficandproductivity,etc.

f)Newinvestmentrequired:descriptionandjustificationofnewinvestment(e.g.inthesectorsofinfrastructure,rollingstock,facilities,etc.),estimatedadvantagesandbenefitsfromeachinvestment,sources(state-private)ofinvestmentandguaranteesoffinancing,expectedreturnofinvestment,volumeofloans.

g)Forecastofevolutionofthevariousfinancialindicessuchas:revenues,expenses,yield,investment,cashflow,etc.

h)Humanresourceschanges.i)Sensitivityanalysesforallforecasts,i.e.howwillchangeaforecast(e.g.ofrevenues)ifabasicassumptionoftheBusinessPlan(e.g.volumeofinvestment,volumeoftraffic,etc.)changes.

Planningproceduresvarywiththesizeoftherailwayundertaking.Whateverthesizeoftherailway,however,itisvitalthattheplansproducedhavethefullsupportofthoselevelsofthepersonnelwhoactuallydothework,canmanagethechangestowhichtherailwayhastorespond,orcanbemaderesponsibleforinternalchanges.

6.5.Projectmanagementforrailways

6.5.1.Definitionofprojectmanagement

Aprojectusuallystartswithanidea,whichisthenelaboratedinastudyandfinallyisdevelopedtothestageofimplementation,completionandoperation.Aprojectimpliesamajorcapitalinvestmentanddiffersfromnormalworkinseveralaspects,suchassize,cost,complexityandcriticality(concerningpartialdeadlinesandfinalcompletion).Anyproject,howeversmall,needseffectivemanagement,ifitistobecarriedoutsuccessfully.Aprojectpresentsadegreeofcomplexityandusuallyitisdifficultforittobecarriedoutbystaffinchargeofdailyandroutinework.

Projectmanagementistheartofdirectingandadministeringaproject.Itcoversthenecessitytodefine,formalize,controlandcoordinateawiderangeofactivities.Itconstitutesbreakingdownthewholeprojectintoeasilyunderstoodandmeasurableworkitems,sothatthetasksandresponsibilitiesofeachteamunitcanbeclearlydefinedandfollowedup.

Thecostoffailureofaprojectisenormousandtherearenotmanyvolunteersintheadministrationthatwouldundertakeiteagerly,withvagueresponsibilitiesdispersedinvariouslevels,whichareidentifiedwithdifficulty.Projectmanagementisawisesolution,whichpermitstheadministration(e.g.infrastructuremanager,ministry,etc.)toefficientlyorganizethevariousteamunits,tooptimizemethodsofwork,andmonitor,analyze,andfollowtheprogressofwork.

6.5.2.Scope,benefitsandcostsofprojectmanagement

Itistheresponsibilityoftheadministrationtoassesswhetherornotitsorganizationalstructure,temporarilyenlargedasnecessary,canefficientlydevelop,plan,administerandsuperviseaparticularproject,whilekeepingitonscheduleandwithinbudget.Thisassessmentshouldbeasobjectiveaspossibleandtheadministrationshouldbeassistedinitsdecisionbyconsultantsspecializedinmanagement.

Projectmanagementhasclearadvantagesinanumberofsituationssuchaswhen,(131):–themagnitudeoftheprojectislargeinrelationtotheadministration’smanagementstructureandsize,

–thescopeofworkisunfamiliartoin-housepersonnel,–ifmanagementisconductedbytheadministration’spersonnel,evenwithadditionaltemporarystaff,theroutineday-to-dayfunctionsriskbeingleftbehind,

–unpredictabledelaysarise,thusnecessitatingrigorousprogramming,

–highpoliticalrisksmayemerge,iftheprojectisdelayedorfailed,–independentandimpartialrecommendationsarerequiredbybanksorotherfundinginstitutions.

Thus,whenmanagementservicesareengagedinaproject,thisoffersadditionalguarantiestotheadministrationforthesuccessfulexecutionoftheprojectandalsootherbenefits,suchas,(131):animpartial,objectiveandprofessionalapproach,experienceoftheprojectmanager,arisingfromsimilarprojects,evaluationofallavailablealternatives,intimemonitoringofdeficiencies,testingandqualitycontrol,closebudgetcontrol,financialforecastingandcashflowrequirements,followingupoftheprogrammingoftheprojectandcompletiononschedule,economies,duetotheopeningoftheprojectmanagertomorecompetitors,reductionoftheriskofdelayingorfailingtodelivertheproject.

Projectmanagementservicesmayappearasanexpensivesolution.However,experiencefromseveralprojectshasprovedjusttheopposite.Inadditiontoassurequalityandin-timedelivery,projectmanagementmaycontributetothereductionofcosts.Furthermore,itshouldnotbeforgottenthatiftheadministrationconductsthemanagement,manyadministrationcostsareeffectivelyhidden.

6.5.3.Somerailprojectsthatcouldrequireprojectmanagement

Projectmanagementmaybebeneficialornecessaryforanumberofrailactivities.Wewillmentionsomeofthem:•constructionofanewhigh-speedline.Suchaprojectrequiresawiderangeofprofessionals,amongthemeconomists,planners,civilengineers,electricalengineers,accountants,architects,sothatprojectmanagementisquasiinevitable,

•trackupgrading.Manyrailwaysstillhaveamilitarydisciplineandinflexibleinternalorganization.Furthermore,theirstaffcontinuestobelievethatrailwaysareanengineeringorientedbusiness.Withinsuchastructureandwhentheneedforupgradingatrackarises(e.g.increaseofspeed,axleload,etc.),itislikelynottochoosethebestsolution.Therefore,open-minded,objective,opentoallsolutionsprojectmanagementwillthenbenecessary,

•anewmarshallingyardorotherfreightfacilitywillnecessitatetrackandrollingstockspecialists,goodinterfacewithroadfreightfacilities,operating

conditionsunderlowcosts.Insuchsituations,theservicesofaprojectmanagerwillbeindemand,

•anewtunnelorbridge.Tunnelsandbridgesareveryexpensiveprojectswithalonglifetime(50÷100years),requiremanyspecialistswithahighlevelofexpertiseandwouldneedprojectmanagementservices,

•anewrailwaystation.Notonlyarchitectsandcivilengineers,butalsocityplanners,transportationengineers,andmarketingandadvertisingspecialistscouldbesoughtinprojectmanagementservicesforanewstation,

•electrificationofaline.Thedecisionofwhethertoelectrifyalineornotisprincipallyamatterofcost.Itshouldbebasedonthevolumeoftraffic,additionalcostforitsimplementation,andthepotentialofloweroperatingcosts.However,powersupply,transmissionsystem,pantograph,insulation,choiceamongthemanyalternativetechnicalsolutions,andtheinterfacewithtrackandinteroperabilityareallveryspecializedissuesthatrequireahighexpertisebutalsothebestcoordinationandmanagement,

•signalingandsafetyinstallationsareextremelycomplexsystems,whoseperformance,reliability,impactonsafeoperation,andtechnologicaladvanceswillrequireprojectmanagementservices.

6.5.4.Adescriptionoftasksofprojectmanagementforrailways

Inthefollowingpageswewillpresentsometasksofprojectmanagement.Thecaseofservicesrenderedtotheinfrastructuremanagerfortheconstructionofahigh-speedlinewillbetakenasacase-study.

Theactivitiesofprojectmanagementcanbedividedinfourstages:Organization,Development,SettingupandExecution.Eachstagebeginswithassessmentandconclusionsofworksoftheformerstageandendswiththesubmissionofareporttotheinfrastructuremanager,(130),(131):

1stStage:Organization.Itcomprisesthefollowingtasks:Definitionoftheprojectandofitscomponents(e.g.foranewhigh-speedline:expropriations,technicalstudiesandsurveys,studiesandselectionoftheappropriatematerialsforsubgrade,ballast,sleepers,fastenings,rails,designoftunnelsandbridges,designofsignalingandelectrificationequipment.Definitionofrequirementsandobjectivesoftheinfrastructuremanager(e.g.costandtimerestrictions,eventualdeficienciesinpersonnelandstaffoftheinfrastructuremanager,etc.).Conceptualplanning(e.g.theprojectmanagerplansitssuccessivetasks:

studies,procurementofmaterials,phasesofexecution,etc.).Activityplans,teamcompositionandresources(e.g.theprojectmanagerplanseachactivity,allocatesresponsibilitiestohispersonnelandprovidesthenecessaryresources(suchasfundingfromtheinfrastructuremanager)).Determinationofphysicalconstraintsandapprovals(e.g.expropriations,licensesfromvariousauthorities).Costevaluationandassessmentofimplications(e.g.theprojectmanagerchecksandchangesthevariouscostestimatesoftheinfrastructuremanager).Programmingofworks,funding,allocationofresources(e.g.manycomputersoftwarecancontributetoarationalprogramming).

2ndStage:Development.Itcomprisesthefollowingtasks:–Designandconstructionstandardstobeadopted(e.g.doestheinfrastructuremanagerhavetheappropriatespecificationsorshouldspecificationsofanotherrailwayauthorityorinstitutionbefollowed?).

–Furtherstudiesandsurveystobecarriedout(e.g.inareasofseismicity,moregeotechnicalinvestigationsmayberequired).

–Finalizationofalternativestrategies.–Finalizationofadministrativeproceduresandapprovalsfromthevariousauthoritiesinvolved(e.g.ministries,municipalities,stateinstitutions,etc.).

–Proposalsforprocurementofthevariousmaterials(e.g.detailsconcerningbiddingprocedures,legislationrestrictions,etc.).

–Allocationoftasksforeachteamunitoftheprojectmanager.–Preparationoftargetcostestimatesforthevariouscomponentsoftheproject.

3rdStage:Settingup.Itcomprisesthefollowingtasks:•Procurementplan(e.g.forballast,sleepers,rails,etc.).•Qualityassurance(e.g.thatballasthastheappropriategeometricalandmechanicalcharacteristics).

•Calculationofquantitiesofthevariousmaterialsrequired.•Costcontrolsandexpectedmarginsofvariation.•Sitemanagementorganization(e.g.whowillbeinchargeofwhat).•Invitationoftendersforthevariousworkcomponents.•Analysisofoffersandresultsoftenders,recommendationsandsuggestions.•Finalestimationofcostsandofcashflow.•Finalizationofscheduleofworks.•Reviewandfinalizationofplanning,whichmaychangeaccordingto

bidders’offersandproposals.4thStage:Execution.Itcomprisesthefollowingtasks:Awardingofcontractsandissuingofinstructionsforwork.Eventualmodificationstodrawingsandexecutionmethodsinrelationtoproposalsofthebidders.Finalizationofinstructionstoavoidaccidentsandensurehealthofallworkingpeople.Establishmentofallrequiredmedicalfacilitiesandpersonnel.On-sitequalitycontrolofmaterialsandsuppliers’works.Appointmentandsupervisionofsitestaff.Monitoringandreportingprogressagainstworkschedules.Reschedulingifitprovesnecessary.Measurementofquantities,calculationofpaymentsandadjudicationofclaims.Finalizationofexpenditureagainstfinalcostestimates.Collectionofdataandrecordsconcerningallsiteworks.Inspectionandacceptanceofpartialdeliveriesofcomponentsoftheproject.Testrunsandcontrolofoperatingconditions.Deliveryofthefinishedprojecttotheinfrastructuremanager.

6.6.Managementofinfrastructure

6.6.1.Tasksandobjectivesforrailinfrastructure

Theprimarytasksofrailinfrastructureare:•toensuresafeoperationofrollingstockatthescheduledspeed,•toaffordconditionsforthehighestqualityoftransport,•tocontributetoasustainabledevelopment.

Principalobjectivesthatinfrastructuremanagementshouldrespondtoare:tomaintainandincreasehighlevelsofsafety,toreducecosts,withouthoweverloweringsafetystandards,toimproveorganization,materials,equipmentandpersonnel’squalificationsinordertorespondmoreefficientlytotherequirementsofoperation,todefineandfollowapolicywhichbalancesrevenuestoexpenses.Theissueofdefinitionofwhatbelongstoinfrastructurehasbeenanalyzedin

section3.5.Thus,managementofinfrastructurecanrefertothefollowingcomponents:–maintenanceandoperationoftrack,–maintenanceandoperationofelectrificationequipment,–maintenanceandoperationofsignalingequipment,–managementofrailtraffic,–allocationofpaths,whenmanyrailoperatorsareaskingforthesameslotconcerningdepartureorarrivaltime,

–computationandcollectionofchargesfortheuseofinfrastructure,whenaseparationofinfrastructurefromoperationexists.

However,therearedifferentapproachesconcerningrailwaystations.Somecountries(e.g.theUnitedKingdom)considerstationsasacomponentofinfrastructure.Othercountries(e.g.France,Sweden,etc.)considerstationsasacomponentofoperation.Certaincountries(e.g.Germany,Italy,etc.)havecreatedanindependentbodyinchargeoftheoperationofstations.

6.6.2.Anewmanagementapproach

Infrastructuremanagersandstaffshouldgetridofoldmethodsandideasinheritedfromthepast.Evenifengineeringaspectsmaybecritical,theyshouldnotdriveandorientinfrastructure’smanagement.Infrastructureexiststoservetheoperationoftrains,whichmustbethedrivingfactorinallkindsofdecisions.Withinthisview,eachinvestmentortechnicalimprovementshouldrespondtospecificgoalsofpassengerandfreightoperation.Thus,thecreationofanewentrepreneurialspiritisthefirsttask.Evaluationofneedsmustbeginfromzero.Everycostcomponentshouldbejustifiedandexaminedinrelationtowhatisthemostprofitable,tobeexecutedbyin-housepersonnelorbyexternalcontractors(outsourcing).Eventhoughrailwayswereincontrolofeverythinginthepast,nowadaysthepicturehaschangeddrastically,(15).

Infrastructureexpensescannolongstayoutofcontrol.Theyshouldbecalculatedindetailforeachcomponent.Thelong-termtargetshouldbeanequilibriumbetweenexpensesandrevenues,thelatteroriginatingfrominfrastructurecharges(paidbyoperators),commercialactivitiesandstatefunding(whichwillbemoreandmorereduced).

Infrastructurechargingpoliciescanhavetwostrategicalternatives:–highcharges;thisalternativeisbeneficialforinfrastructurefinances,butdetrimentalforoperators,

–lowcharges;thisalternativeisdetrimentalforinfrastructurefinancesbut

beneficialforoperators.

Theorganizationofpersonnelmustalsochange.Inthepast,criticalfactorsforpromotionwerequalificationsandthenumberofyearsofpreviousservice.Todayandinthefuture,promotionisachievedinrelationtoskills,responsibilitiesandproductivity.

EachinfrastructuremanagermusthavehisownBusinessPlan.TheinteractionofthevariouscomponentsofinfrastructureisillustratedinFigure6.6.

Fig.6.6.Interactionofthevariouscomponentsofinfrastructure,(126)

6.6.3.Theissueofoutsourcing

Maintenanceandoperationofinfrastructureisalaborintensiveactivity.InEurope,40÷60%ofinfrastructureexpensesarepersonnelsalaries.Workingconditionsformaintenanceareextremelydifficultattheavailabletimebetweensuccessivetrains(usuallyduringthenight).Withonetrainpassingperhour,efficiencyofworkingpersonnelis80%,whilefortwotrainspassingperhour,thisefficiencyisreducedto50%.

Manyinfrastructuremanagersfollowapolicyofoutsourcing,whichconsistsinaskingforanoutcontractor’sservices(usuallythroughabiddingprocedure).Outsourcingpolicyisappliedtoactivitiessuchasthemaintenanceoftrack,tunnels,bridges,etc.Outsourcingpolicieshavepermittedhighreductionsof

costs,astherightprojectisexecutedattherighttimeandattherightprice.However,outsourcingshouldnotaffectsafety.Infrastructuremanagersmustimposespecifications,conditionsofworkandsupervisionforoutcontractors.

6.6.4.Theneedforanhomogeneousrailproductattheworldlevel

Railwayshavebeendevelopedonmanyoccasionstomeetnationaltargets.Thus,whencrossingafrontier,railinfrastructuremaybeofatotallydifferentqualityfromonecountrytoanother.Intheeraofinternationalrailwaycooperation,however,infrastructuremanagersshouldseekforcollaborationinordertoachieveasimilarqualityofinfrastructurefromorigintodestination(whichoftenmeanscrossingmanyfrontiers).Thishomogeneousrailinfrastructurewillrequire:•aqualityoftrackmaintenance,whichhasasaprerequisitethattrackdefectsareofthesamemagnitudeeverywhere,

•electrificationandsignalingsystemsthatpermitacontinuousrunningoftrainswithoutanyinterruptionfortechnicalreasons.Technicalinteroperabilityisthetooltotackleincompatibilitiesconcerningtrackgauge,electricpowerandsignalingsystemsfromonerailwaytoanother,

•technicalfacilitiesthatgivetheclienttheimpressionofanhomogeneousinfrastructure.Thisappliesbothtopassengerbutalsotofreight(appropriateterminalandtransshipmentsystems).

6.7.Managementandpolicyforrailpassengertransport

6.7.1.Tasksandobjectivesforrailpassengertransport

Railpassengertransportmuststruggleinordertocompeteinachangingenvironment,whichthreatenseventheexistenceofsomerailwayservices.Theprimarytasksofrailpassengertransportare:–safetransportofpeopleatthescheduledtime,–highqualityofservice,whichshouldbeatleastsimilarorevenhighercomparedtotherailway’scompetitors,

–contributiontoregionaldevelopmentandtotheincreaseofmobilityforcertaincategoriesofcitizens,

–increaseofrevenues.

Principalobjectivesthatmanagementofpassengertransportshouldrespond

toare:•increaseofshareofrailwaysinthepassengertransportmarket,whichattheEuropeanUnion(15countries)leveldecreasedfrom10.4%in1970to6.7%in2010,

•increaserailyield,thatisunitrevenue,•reductionofcostsinordertobalanceexpensesandrevenues.Hugedeficitscannotcontinuetoexistandinanycasetheyshouldbeclarified.Thestatecancontinuetofinancesomerailserviceswithlowrevenues,withintheframeofpublicserviceobligations.IntheEuropeanUnion,forservicesotherthanthoserelatedtopublicservice,railoperatorsmustsucceedinfindingabalancebetweenexpensesandrevenues,whichbecomesaconditionforsurvival,(15).

6.7.2.Asegmentationoftraffic

Railpassengermarketcanbesegmentedasfollows:–intercitytraffic.Itservesmajorpopulationcentersandcustomersareverydemandingconcerningtraveltimesandqualityofservice.Railwaysfacestrongcompetitioninintercitytrafficfromairplanesandbuses,

–regionaltraffic.Itservesregionalcenters,competitioncomesfrombusesandprivatecars,customers’exigenciesarelower,comparedtointercitytraffic,andmayreceivepublicserviceobligations,

–commutingtraffic.Itservesthesuburbsofacity,competitionalsocomesfrombusesandprivatecarsandusuallyitisstronglysubsidizedbythestate.

Railmanagersshouldconsidertheexpectationsofeachsegmentoftrafficandconductpolicies,whichmaybedifferentfromonecategoryoftraffictoanother.

6.7.3.Anewstrategycombiningcompetition,cooperationandalliances

Fullliberalizationoftherailwaysectorraisesopportunitiesandthreats.Withinthisenvironment,railwaymanagersmustthinkandactquitedifferentlyfromwhattheyhavebeenaccustomedtointhepast.

Competition(bothinter-modalandintramodal)willbetherule.Reductionofcostsandincreaseofqualityofservicearetheleastprerequisitestofacecompetitionefficiently.

Experiencesfromliberalizationofothersectorsoftheeconomy(airtransport,telecommunications,electricity)suggestthatbeforeexpandingtheiractivities,railwaysmustensurethattheycontrolanessentialpartoftheir

domesticmarket.Otherwise,inthecasethattheexpansionleadstofailure,theyrisklosingeventheirdomesticmarket.

Newopportunitieswillbegiven,particularlyininternationaltraffic.Railwaysmustpreparenewproducts(suchasintercityservicesininternationalrouteswithoutdelaysinthefrontiers),whichshouldbedifferentiatedfromthoseoftheircompetitors.

However,competitorsmaybealliesinseveraloccasions.Thus,railandairtransportcancooperateatleastintwocases,(seealsosection1.10):•short-distancerailservicesfromairportstocitycenters,•medium-orevenlong-distancehigh-speedrailservicesfromairportstoothercities.Railwayscanalsocooperatewithbuses,whichcantransportpassengers

fromstationstotheirfinaldestination,assuringinthiswayadoor-to-doortransport,somethingthatrailwayscannotofferbythemselves.

Competitionandcooperationwillrequirechangesinthestructure,organizationandlegislationofrailways,whichusuallytaketime.Railwaymanagersshouldbepreparedforit.

6.7.4.Traditionalweaknessesandofferofanewglobalproductofrailways

Arailwaytripisonlyapartofamorecomplextripfromorigintodestinationincludingothertransportmodessuchasbus,taxiandmetro,(seesection5.1.5).

FactorsdeterringcitizensfromusingtherailwayhavebeenstudiedandarepresentedinTable6.1,(80).

Inordertoalleviatetheseweaknesses,railwaysshouldtrytoofferanewandglobalproducttocustomersbytakinganumberofmeasuresinorderto:–makerailwaytriporganizationandticketingeasier,–improvefacilitiesinrailwaystations,–improveaccessibilitytopublictransportnetworks,suchasbuses,metrosandtaxis.

Thus,manyrailwayshaveestablishedandmaintainwebsiteswithusefulandeasy-to-obtaininformation,manyofwhichalsoprovideticketingservices.Concerningticketing,manystationshavebeenre-organizedwiththeuseofqueuingsystems,haveexpandedtheuseofinformaticstechnologies,andhaveintroducedinnovativewaysofissuingtickets,suchasautomatictellers.Tohelpthetravelerathisfinaldestinationandincreasetheticket’sperceivedvalue,somerailwayshaveextendedthevalidityoftherailticketforpublictransport,(123).

Table6.1.Railwayusagedeterringfactorsandthegradeofdiscomforttheycause(5:

fullsatisfaction,0:nullsatisfaction),(80)

Railwaysmustimperativelyreducedistributioncosts.Formostrailoperators,30÷60%ofexpensesareduetostaffcosts;thustheintroductionofinformaticstechnologiescangreatlyimproveproductivityandreducecosts.

6.7.5.Applicationofinformaticstechnologies(internet,SMS)

SomerailwayshavemodernizedtheirdistributionchainbyusingtheinternetorSMS,followingastrategyofofferingmonetarybenefitsbothtotherailwaycompanybutalsotothecustomers,bycreatingagapinthelevelsofpricesofticketsdeliveredinstations,accordingtotheusualoldway,andthosedeliveredwiththeuseofinternetorSMS.

Thus,inGermany,pricesofticketspurchasedontheinternetare5÷10%lowerthanforthesameticketsdeliveredinstations.IntheNetherlands,asurchargeof0.50€(andinsomecasesof1€)istobepaidifticketsareissuedinstations(disabledandpeopleolderthan60yearsdonotpaythissurcharge).

Insomerailways,theclientcanreserveaseatandpurchaseaticketwithaspecificSMSmessage,whichissenttotheappropriaterailwaycall-center.Inexchangeandafterhavingpaidtheamountoftheticketwithacreditcard,thecustomerreceivesaspecificcode.Thiscodewillbegiventothecontrolleronthetrain,whowillcheckthevalidityofthecodewithaspecificpocketcomputer.Inaddition,theclientcanchangeorcancelhisreservation.

However,notallclients(particularlyoldones)caneasilybeaccustomedtonewtechnologies.Forthisreason,andinordertoavoidtheclients’annoyance,itissuggestedthatrailwayauthoritiescreateinthestationsreceptionareaswithassistantsadvisingpeoplehowtousetheinternetorSMS.

6.7.6.Marketing–Customersatisfactionsurveys–Creationofanewculture

Asexplainedinsection4.3.1,railwaymanagers,inordertomonitorclients’reactionsandadaptrailwayofferstotheirexpectations,mustusecustomersatisfactionsurveyssystematically.Asmanymarketingcampaignshaveshown,improvingaproductandpromotingitisnotenough;itshouldbeintegratedwithinanewspiritandanewcultureoftherailwaycompany.Thus,railwayscancreateanewlifestyle:anenvironmentallyfriendlytransportmode,whichrespectsclients,transportsthemwithpunctuality,safetyandsecurity,withlessstressandmorecomfort.Railwaypersonnelmustsharethevaluesofthisnewculture,(15).

Withinthisnewspirit,someactivities(suchascleaningoftrains,maintenanceofrollingstock,etc.)maywellbeoutsourced.

6.8.Managementandpolicyforrailfreighttransport

6.8.1.Tasksandobjectivesofrailfreighttransport

Theprimarytasksofrailfreighttransportare:–safetransportofgoodsanddeliveryatthescheduledtimewithoutanydelayoranydamagetothecontentofthefreight,

–contributiontoasustainabledevelopment,particularlybytryingtoreducethenoiselevelfromfreighttrains,whichusuallyoperateduringthenight.Theprincipalobjectivesthatrailfreightmanagementshouldrespondtoare,

(117):•reducingcosts,whilecontinuingtoimprovesafety,•asinmanycountriesofEuropeanUnion,theUSA,etc.,railfreighttransportcannotreceivepublicsubsidies,thusrevenuesfromthefreightactivityshouldbalancecosts,

•increaseofpunctualityandreliability.Thisdoesnotmeannecessarilytheincreaseofspeedoffreighttrainsbuttheeliminationofwaitingtimes,

•improvementoforganizationandintroductionofappropriateequipmentinordertorespondtoclients’requirements.

6.8.2.Amercilesscompetition

Inadditiontoexternalcompetition(fromroadtrucks),railfreightmarketisafieldofastrongcompetitionbetweentheestablishedstaterailwaysandprivateentrantsintherailfreightmarket,whichofferforcertainkindsoftraffictariffs10%÷50%lowerthanthestate-ownedrailways.

Formanydecades,railwayshavebeenlosingfreighttraffic,astheircompetitorswerelessexpensiveandmorereliable.Evenformarketsforwhichrailwayshaveacomparativeadvantage,e.g.massivetransportofbulkmaterials,theriskandthefearofstrikesledsomeoftheirclientstodismisstheuseofrailways.Inordertoreversethissituation,railfreightmanagersshouldundertakeanumberofpainfulmeasures,suchas,(117):–ensuringthedeliveryofgoodsatthescheduledtimebyreimbursingclientswithamountsdisproportionatelygreaterthanthevalueofrailtariffsinthecaseofdelays,

–increasingproductivitybyadoptingpoliciesinwhichtraindrivers,inadditiontodriving,offerservicesofinformingtheclient,assemblingthecargo,etc.,ifthisprovesnecessary,

–promotingcooperationwithcompaniesofroadtrucksinordertoofferadoor-to-doorfreighttransport.

6.8.3.Integrationofrailfreightinthelogisticschain

Figure6.7illustrateshowrailfreighttransport(whichisnotapurposepersebutonlyasegmentofatransportfromorigintodestination)canbeintegratedinthelogisticschain(seealsosection1.9.5)inordertosucceedon-timedeliverysimilartothatofroadtransport.

WiththeexceptionoftheUSA,mostoftheothercountrieshavegivenprioritytopassengertransport.Thus,freightisobligedtooperateduringtheavailableintervalsamongpassengertrains.Toovercomethissituation,railfreightmanagersmustputpressureoninfrastructuremanagerstoseparateslow(freight)fromfast(passenger)traffic.Forheavyroutes,thecreationofrailcorridorsdedicatedonlytofreighttransportmaybeexamined.

Fig.6.7.Railfreightandthelogisticschainfromorigintodestination,(126)

6.9.Humanresourcesandtheirrevalorization

6.9.1.Theneedforamoreentrepreneurialapproach

Formanyrailwaysandformanydecades,thenumberofstaff,theirqualifications,workingconditionsandpromotionweretoacertaindegreearesultofhierarchy,politicalandsocialconsiderations.Asaconsequence,somerailwaysexperiencethediseaseofovermanningwithunqualifiedstaff,resulting

inlowproductivityandalowqualityproduct.Suchasituationisnotacceptabletoday,ifrailwayswantreallytosurviveinanextremelycompetitiveenvironment,wherecompetitorsemploypeopleinamorerationalway.

Financialconstraintsrequirerailwaymanagerstoreducecostsandtomaximizetheuseofhumanresources,sothatadditionalresourcesareaddedorsoughtonlyiftheycanbejustifiedbycontributingsignificantlytoanincreaseofoutput.Thetargetshouldbetosucceedanallocationoftaskswithinaworkingorganization,whichattainspredeterminedproductiontargetsbyusingtheminimumlevelsofstaffandworkingresourcesatthehighestworkrateforthelargestpossibletimeandfortheminimumcost,whilerespectingtechnicalspecifications.Althoughthisisanutopia,itshouldbethetarget,(130).

6.9.2.Allocationofhumanresources

Inasimplebusinessitiseasytoidentifyneedsandtasksandallocatetheappropriatehumanresources.Thebiggerthebusiness,(railwaysareindeedabigbusiness),themoredifficultitistoobtainanoptimumallocationsolution,sincetherearesomanydecisionstobemadeaboutamultitudeofresources,mostofwhichinteractwitheachotherinacomplexway.

Allocationofresourcescanbeachievedwiththeuseofoneofthefollowingmethods:pastexperience,guessing(notrecommended),networkanalysis,linearprogramming,simulationandmathematicaloptimization.Withtheexceptionofmethodsbasedonexperienceandguessing,allothermethodsrequirecomputersoftwarethathavebeendevelopedeitherbytherailwaysorbyoperationalresearchteams.

Concerningthelevelofresourcesallocation(national,regional)therearetwoapproaches,(130):•theonesuggeststhattheuseofstaffatlocallevelisscheduledingreatdetailwiththeuseofcomputermethods,regionalmanagershavingsmallpossibilitiestoalterallocationsdonebycomputers,

•theotherusesalsocomputercalculationsatnationallevel,butgrantshigherauthoritytoregionalmanagersforanoptimumallocation.

Resourcesallocationcanbedoneonashort-termoronalong-termbasis.Apartoftraincrewandmaintenancepersonnelisemployedinsomerailwaysonatemporarybasis,duetorequirementsatpeakperiods.

Resourcesallocationmusttakeintoaccountothercomponentsoftherailwayactivity,suchasleveloftechnology,equipment,materials,etc.However,humanactivityismoreandmorereplacedbymachines.Electronicticketing,for

instance,ortheuseoftheinternetwillgreatlyreducethenumberofstaffinchargeofsellingtickets.

Theformofthecontractwithemployeesdependsnotonlyontheneedsbutalsoonthetermsoflaborlegislation,whichinrecentyearshasbecomemoreflexible.

Selectionoftheappropriatehumanresourcesshouldaccountforthefollowing:skills,experience,personalincentives,unitcosts,possibilityofalternativeoutsourcing(e.g.cleaningofstations),laborlegislationandunions’attitudes.

6.9.3.Theartofmotivatingpeopletowork

Motivationistheprocessbywhichstaffandworkforcearestimulatedtoworkasfastandpurposefullyaspossible.Motivationistriggeredbyseveralfactors,suchas:levelofsalary,incentives(e.g.,bonuses)forhigherproductivity,jobsatisfaction,statusandsenseofidentity,workingenvironment,senseofpurpose,opportunitiesforadvancement,workingrelationships,socialandwelfarefacilities,performanceappreciation,andstabilityofemployment.However,itisgenerallyeasiertorecognizesymptomsofdemotivationsuchas:timewasting,absenteeism,poortimekeeping,poorqualitywork,non-cooperation,declineinpersonalappearance,etc.,(130).

Manyrailwaymanagersdonotpayasmuchattentionastheyshouldtotheworkingenvironmentoftheirstaff.Theyforgetthatthehighestlevelsofproductivityareattainedbypeoplewellpaid,welltrained,contented,confident,andequippedwiththenecessaryequipment.Lackofinterestintheworkingenvironmentresultstodemotivationonthepartoftheirstaff.

6.9.4.Increaseofproductivity

Aprincipalobjectiveofresourceallocationistoachieveanincreaseinproductivity.Infact,productivityrelatesthetrafficproduced(passengers,passenger-kilometers,tons,ton-kilometers)tothenumberofstaffusedtorealizethistraffic.Productivitycanalsorelatetheworkproducedtothecostofproductionortotheequipment(rollingstock,etc.)usedtoachievethisproduction.

Increaseofproductivitywiththebestuseofavailablestaffandequipmentimpliesoptimizationofthefollowing:–organizationstructure,inordertoensureaminimumoftimelossesbetweensuccessiveactivities(e.g.cleaningandcheckingofrollingstock,laying

continuousweldedrailsandfinishingwithballastlayingandcompaction,etc.),

–planning,inordertominimizetimelossesamonginteractiveactivities,–communicationfacilitiesandchannels,–increasespeedandrateofwork,–regulartraining,particularlyifnewtechnologyhasbeenintroduced,–creationofanenvironment,whichensureshealth,safetyandwelfare,–supervisionanddisciplinaryprocedures,–reductionofoverheadcosts(comingfromadditionalworkinghours,normallyunnecessaryintheproductionprocedure),

–reductionofunitcosts,somethingthatwillprovokethereactionofunions.

6.9.5.Restructuringandrevalorizationofhumanresources

Organizationinmanyrailwaysischaracterizedbyinflexibility,excessofpersonnel(usuallyinroutineworks),lackofspecializedpersonnel(usuallyinmanagement,marketingandoperationofhightechnologies)andagapbetweenresponsibilitiesandlevelofskills(aresultofthelackofre-trainingformanyyears).Laborrestructuringandrevalorizationareamongthefirstprioritiesofrailwaymanagersandcomprisethefollowing,(15):•goodunderstandingofthenationalandinternationaleconomicenvironment,•estimationoffuturerailtransportdemand,•calculationofrequiredstaffandoflevelofoutsourcingactivities,•estimationofexcesslaborandsurplusassets,•guessofpoliticalintentionsofstateofficialstosubsidizeloss-makingservicesandactivities,

•networkrationalizationanddefinitionofanewcultureforrailservicesofferedtoclients,

•withdrawalofunprofitableactivities,•descriptionofnewservicesandproducts,•restructuringofexcesslabor.Optionsthatcanbedeployedare:transfertoothercompaniesorstatedepartments,creationofnewactivities,dismissalofstaff,whichshouldbethelastsolution,sinceitwillprovoketheunion’sreactionsandsocialunrest.

•organizationalchanges,suchaslocationofwork,hierarchyposition,levelofresponsibility,etc.,

•necessaryre-training,

•estimationofcostandtimerequiredtoimplementchanges,•acommercialorientationofallunits(includingthetechnicalones)atthelowestleveloftheorganizationoftherailwayactivity,

•assessmentoftheimpactofrestructuringonproductivity,revenuesandproductioncosts,

•creationofanewphilosophyandcultureofemployees,whichshouldplacetheserviceofclientsatthecenteroftheirresponsibilities.

Intheplanningoftheirrestructuringstrategies,railwaymanagersshouldnotneglectthat:–institutionalfactorsmayseriouslyconstraintheabilityoftherailwaystorespondtochange.Suchfactorsare:laborlawrestrictions,unions’defenseofcurrentworkingpractices,apoliticalenvironmentsupportingsocialemploymentpolicies,

–downsizingofrailwaysisnotpossible,unlessastrongpoliticalcommitmentcanbeassured.

6.10.Privatizationofrailways

6.10.1.Prerequisitesandtargetsofprivatization

Thesolepurposeofaprivatecompanyistomakeaprofit.Allothermotivationsareofsecondaryimportanceandtheydonotexistunlesstheprimaryconditionofprofitiseitherarealityorastrongandforthcomingexpectation.Inviewofthis,thequestionishowprivatizationcanworkwithdeeplyloss-makingrailways.

Inmostcasesoftheprivatizationofrailways,thedeparturepointwasofideologicalnature:itwassuggestedthatrailwaysshouldbeconsideredinthesamewayasotherservicesactivities(telecommunications,airways,etc.),whileleavingasidetheparticularlycomplexcharacteroftherailwaysystem.

Whetherideologicalornot,theprocessoftheprivatizationofrailwayshasmanytargets:–cutcosts,reducedeficitsandconsequentlystatesubsidies,–introduceinnovationsandincreaseperformancesofrailways,–attractprivatecapitalsforinvestment,–getridofinertiaandofthepoliticallobbyingofrailways,thoughthelastisrarelysaidpublicly.Thedesiretoprivatizerailwaysisnotenough.Anumberofprerequisite

conditionsshouldbemet,(66):•theprivatizedactivitymustgenerateakindofprofit,•theprivatizedrailwayenjoysfullfreedomofmanagementandoperatesinaccordancewithcommerciallaw,

•publicserviceobligationsareeitherabolishedorproperlycompensated.Theseprerequisitesarevalidwhethertheyconcern\astate-ownedrailwayor

anewentrantinthemarket.

6.10.2.Privatizationandcompetition

Privatizationisnotaconditionforcompetition,whichmaywellexistbetweenstate-ownedrailwaycompanies(governedbythesamerulesasprivatecompanies)andnewprivateentrantsinthemarket.Itistheresponsibilityofthestatetoestablishclearconditionsofcompetitioninthemarket.Butusuallythestatefailstodosoandpresentsprivatizationasaconditionofcompetition,somethingthatisnottrue.

6.10.3.Theproblemofdebt

Inmostcases,(Germany,etc.),thestatehasundertakentheaccumulateddebtofthestate-ownedrailway,thusgivingagreaterchanceforthesuccessofprivatization.Thiswas,however,notthecaseintheprivatizationofJapaneserailwaysin1987,whosedebtwasmorethan10%ofJapan’sGDP.Intheprivatizationprocedure,40%ofthedebtofJapaneseRailwayswastransferredtothethreemostpowerfulandpromisingofthesixnewrailwaycompanies(inchargeofbothinfrastructureandpassengertraffic),whiletheremaining60%ofthedebtwasassumedbyanewgovernmentorganization.However,theJapanesecaseisanexception.

6.10.4.TheneedforastrongRegulator

AliberalizedmarketneedsaRegulator.Thisisevenmorethecasewhenprivatizationproceeds.TheRegulatorshouldassurethefollowing:–protectallpersonsfromanydangerandensurehealthyandsafeconditionsoftransport,

–protectallkindsofinterestsofusersofrailwayservices,–imposeonoperatorstheminimumrestrictionsconcerningperformances(e.g.,qualityofservices).

–takeallmeasuresforafairandonequalbasiscompetition,

–enableoperatorstoexercizetheiractivityfreelyinanenvironmentofareasonabledegreeofassurance.

6.10.5.Privatizationofinfrastructure

Theprincipalfearforprivatizinginfrastructureisthattheinvestmentchoicesoftheprivateentrepreneurwillbedeterminedsolelyonthebasisofprofitandtheexpectedreturnofinvestedcapital,whileneglectingaspectsofmaintenance,whichmayhaveacatastrophiceffectonsafety.TheBritishattemptatthefullprivatizationofrailinfrastructurewasfinallyabandoned,astheminimumstandardsimposed(bythestate)onmaintenancedidnotpermitenoughbenefits,inspiteofratherhighinfrastructurechargespaidbyoperators.

Theotherextreme,keepingunchangedtoday’ssituation,isuntenable.Inmostcases,railinfrastructurewillremainunderstatecontrol,butasignificantpartofitsactivitiesmaybeoutsourcedtotheprivatesector.

6.10.6.Privatizationofoperation

Activitiesofoperationthatmayattracttheprivatesectorare:high-speedservices,especiallyoverlongdistancesorinternationalroutes,somelocalpassengerservices,somecategoriesoffreight(bulkvolumes,combinedtransport).

Regionalandurbantrafficarenotusuallyattractivefortheprivatesector,astariffsarelow,unlesstheyarestronglysubsidized(throughacompetitiveopenbiddingprocedure)bythestate.

Apartialprivatizationofsomeactivitiesofoperationhasaninherentdanger,tosplitrailwayservicesintwocategories,(66):–thepartunderprivatecontrolwillenjoyinvestmentandinnovationandwillincreasethequalityofservices,

–thepartunderstatecontrolwillhavelessinvestmentandmodernizationanditsdecliningcourseriskstobefurtheraccelerated.

6.10.7.Somecasesofprivatizationofrailwaysallovertheworld

ThemostspectacularprivatizationwasthatoftheformerBritishrailwaysin1995.RailinfrastructurewasgiventoRailtrack,aprivatecompany,whichduetoeconomicproblemsandaseriesofaccidentswasre-nationalizedpartiallyin2003(creationofNetworkRail).TheresponsibilityofRailtrackandNetwork

Railwastheprovisionoftrack,stationsanddepotstocompanieswishingtooperatetrains.PassengertrainservicesintheUnitedKingdomareprovided(in2013)by24trainoperatingcompanies(calledTOCs),whichbidedsuccessfullyfortherighttooperateservicesinaspecificarea,foraperiodof4.5to20years,withamediumstatesubsidyof40%,(127).

ThoughtheprincipaldriverfortheprivatizationoftherailsectorintheUnitedKingdomwasthereductionofpublicsubsidiestotherailways,anexpostanalysis(Fig.6.8),illustratesjusttheopposite.Indeed,publicsubsidiestotherailwaysareestimatedtobeafterprivatization3÷4timeshighercomparedtothesituationbeforeprivatization.

Fig.6.8.PublicsubsidiestotherailwaysintheUnitedKingdombeforeandafterprivatizationinthemid-90s

AnothersuccessfulprivatizationwasthatoftheformerJapaneserailwaysin1987,whichweretakenoverby6privatecompaniesforpassengertransport(eachoneowningitsinfrastructure)andonecompanyforfreight(whichpaysfeestousetheinfrastructureoftheaforementioned6companies).

PrivatizationofrailwaysinAustraliaaimedprincipallyatpoliticalgoals:getthegovernmentoutofanykindofbusinessconcerningnotonlyrailwaysbutalsoairlines,ports,banks,etc.Poorfinancialresults,lowproductivity,insufficientinvestmentsintheformerstate-ownedrailwaysfacilitatedgreatlytheroutetowardsrailprivatization.Almostallfreightrailwaysareprivatized,

whereasPPPsschemeshavebeenpromotedtomanyrailpassengerservicesandinfrastructure.Globally,therailprivatizationexperienceinAustraliamaybeconsideredaspositive.Inthecaseoffailures,theprincipalreasonswereunjustifiedoptimismoverestimateddemandandrevenuesandunderestimationofinfrastructurecosts.

PrivatizationofrailwayswasalsosuccessfulinNewZealand,withoutanyclaimfromprivateoperatorsforstatesubsidies.However,whileprofitsappearedinthefirstfewyearsafterprivatization,laterrevenuesdecreasedandgovernmentwasobligedtore-nationalizethetrack.

RailwaysinEstoniaarealsoprivatized,whereasGermanRailwaysarescheduledtoaskfortheparticipationofprivatecapital(throughtheStockMarket)inthecomingyears.

ThesituationintheUSAisdescribedinsection3.8.Freightoperators(eachoneowningitsinfrastructure)areprivatecompanies,whileAmtrak,theFederalpassengerrailoperator,isstronglysubsidized,andrunsonotheroperators’infrastructurebypayingappropriatecharges.

6.10.8.Effectsanddegreeofprivatization

Inalmostallcasesofprivatization,thequalityofserviceswasincreasedandcostswerereduced.Insomecases,subsidieswerereduceddrastically(NewZealand,Australia),whilethisreductionofsubsidieswasnotsospectacularinothercases(UnitedKingdom).Trafficalsoincreased,butitisdifficulttoconsiderthisincreaseasaresultofprivatizationonly.Thebigcontroversyoversafetyandthelossofthebenefitsoftheintegratedrailwaysystemstillremains.Thereisevidencethatafterprivatizationsomeaccidentswerearesultofanabsenceofsynergyamongthevariouscomponentsoftheformerlyintegratedrailway.

Whathasbeenmentionedsuggeststhatprivatizationshouldbeviewedwithcaution,whiletakingintoaccounttheparticularitiesandthepoliticalenvironmentofeachcountry.Therearevariousdegreesofprivatization,fromfulltopartial,andthebenefitsandweaknessesshouldbecarefullyexaminedbothfortherailwaysontheonesideandtheeconomyandthesocietyontheother.

6.11.Justificationandcalculationofpublicserviceobligations

Clarificationoftheeconomicsofrailwaysrequiresajustificationanda

calculationofpublicserviceobligations.Infact,thestatemustensureforeachcitizenaccessibilitytolocalandnationalcenterswithatleastonetransportmode(preferablytwo).Publicserviceobligationsareoftenfoundedontheoriesofregionality,whichhaveagreatrangeofdefinitions.Theoriesofpolarityrelatepopulationcenters(e.g.suburbs,villages,towns)todevelopedpoles(industry,administration,leisure,etc.).Othertheoriesarebasedongeneralizedcostapproaches.Regionalityisaninversefunctionofaccessibility.Publicserviceobligationsmayreferto:obligationstooperaterailwaylines,whichotherwisewouldbeclosed,obligationstotransportsomecategoriesofpassenger(freightisusuallyexcluded)undercertainconditionsandtariffs,obligationstoapplytariffs,whichareimposedbythestate.

Analyticalaccountsarenecessaryforadetailedcalculationofpublicserviceobligations.Thestatecaneitherimposeapublicserviceobligationonarailoperatororchoosethelowestcostoperatorthroughanopenbiddingprocedure.Thestatemustcompensateforeachpublicserviceobligationthedifferencebetweentheadditionalexpenses,causedbythepublicserviceobligation,andtheadditionalrevenuesgeneratedbythem.

7TheTrackSystem

7.1.Thetraditionaldivisionofrailwaytopicsintotrack,tractionandoperation

Formanydecades,theorganizationoftheunifiedrailwayactivityhasorientedrailwayscience,whichisinterdisciplinaryandrequirescompetencesofthesectorsofthecivilengineer,theelectricalandthemechanicalengineer,theeconomistandthemanager.Thus,followingrailwaynetworkorganization,ithasbecomecustomarytodistinguishrailwayscienceintothreetopicareas:Tracktopics.Subjectsofrailwayinfrastructurearedealtwith,inordertoensurethesafeoperationoftherollingstockatthescheduledspeed.Thesuperstructure(rails,sleepers,fastenings,ballastorconcreteslab)andthesubgradearecentralsubjectsoftracktopics.Tracktopicsalsoincludelayout,stations,switchesandcrossings,maintenanceandsafetyissues.Tractiontopics.Subjectsconcerningrollingstockareelaboratedon.Tractiontopicsalsoincludeelectrictraction,telecommunicationsandsignaling.Certainrailways,however,includetheselatterintheareaoftracktopics,sincetheyarepartofthepermanentrailwayinfrastructure.Operationtopics,whichinclude:–Commercialoperation,inwhichcommercialandpricingpoliciesareanalyzed.

–Technicaloperation,whereissuesconcerningscheduleorganization,optimumuseofrollingstockandtrafficsafetyareexamined.

Totheaboveshouldbeaddedthetopicsofmetropolitanrailways(metrosandtramways),whichconstituteaspecificrailwayclassoftheirownofgreatimportancetomasstransitinlargeurbancenters.

However,aftertheseparationofinfrastructurefromoperation,tracktopics,electrification,telecommunications,signalingandtechnicaloperationbelongtotheresponsibilitiesofinfrastructure,whereasrollingstockoperationandmaintenanceandcommercialoperationbelongtotheresponsibilitiesofoperation.Railwaystationsmaybestudiedeitherininfrastructureorin

operation,dependingonthechoiceofwherestationsarebelonging,(seesection3.5).

Inthenextchaptersofthisbookwewilldealwithalltheaforementionedissues,withtheexceptionofstations.Differencesintrackcharacteristicsfromonecountrytoanothercombinedwiththeneedtoaffordaccuratespecificationsforeachengineeringstructurehaveledinternationalinstitutions,suchastheUIC,theEuropeanCommission,andnationalauthoritiesofvariouscountriestodefinespecificationsforeachcomponentoftherailwaysystem.ThespecificationsthatwillbemostusedarethoseofUICandtheEuropeantechnicalspecificationsforinteroperability,(134),(136),(140).

7.2.Thetracksystemanditscomponents

Inarailwaytrack,(Fig.7.1),twodiscretesubsystemsaredistinct:–Thesuperstructure(rails,sleepers,trackbed(ballast,subballast)),whichsupportsanddistributestrainloadsandissubjectedtoperiodicmaintenanceandreplacement.

–Thesubgrade(formationlayer,subsoil),onwhichthetrainloads,afteradequatedistributioninthesuperstructure,aretransferredandwhichinprincipleshouldnotbesubjectedtointerventionsduringperiodicmaintenanceoftherailwaytrack.

Fig.7.1.Thetrack(superstructure–subgrade)system

Thesuperstructureiscomposedof:Therails,whichsupportandguidethetrainwheels.

Thesleepers(alsocalledties,principallyinNorthAmerica)withtheirfastenings,whichdistributetheloadsappliedtotherailsandkeepthemataconstantspacing.Theballast,whichconsistsusuallyofcrushedstoneandonlyinexceptionalcasesofgravel.Theballastshouldensurethedampingofmostofthetrainvibrations,adequateloaddistributionandfastdrainageofrainwater.Thesubballast,whichconsistsofgravelandexceptionallyofsand.Thesubballastprotectsthesubgradetopfromthepenetrationofballaststones,whileatthesametimefurtherdistributingexternalloadsandensuringthequickdrainageofrainwater.Inthesubgradethefollowingaredistinguished:

•Thesubsoil,whichinthecaseofthetracklaidalongacutconsistsofon-sitesoil,whileinthecaseofanembankmentiscomposedofsoiltransportedtothesite.

•Theformationlayer,usedwheneverthesubsoilmaterialisnotofappropriatequality.Thedesignofthetracksystem(choiceofmaterials,dimensioning)should

ensuresafety,passengercomfort,rationalconstructionandoperationcostandtheleastpossibleeffectstotheenvironment(airpollution,sonorpollution,groundvibrations,etc.).

Thedepthtowhichmechanicaleffectsresultingfromtraincirculationoccur,extendstoaround2mbelowthesubgradetop,andthisisthedepthdowntowhichwillhenceforthbereferredtobythetermsubgrade,(148).

Resilientpadsareplacedbetweenrailandsleepertofurtherattenuatetrainvibrations,(Fig.7.2.a).Thicknessesofpadsareusuallybetween5÷10mm.Elasticpadsarecomposedofsomekindofelasticmaterial(rubber,etc.)andinadditiontoattenuatingtrainvibrationstheyprovidesomeinsulationbetweenrail-sleeperandcontributetoamoreuniformdistributionofexternalloads.

Inrecentlyconstructedorrenewedtracks,however,abaseplateisplacedbetweenrailandsleeper,(Fig.7.2.b).Inthiscase,resilientpadsareplacedbetweenrailandbaseplateandbetweenbaseplateandsleeper.

Fig.7.2.Resilientpadsbetweenrailandsleeper

Thesuccessionofthevariouslayersofthetracksystemischaracterizedbyagradualincreaseofthesurfaceareaasweproceedtolowerlayersandbyaconsiderablereductionofthedevelopedstresses,(Fig.7.3).Wetakeintoaccountawheelloadof10t.Thecontactsurfacebetweenwheelandrailisaround1.3cm2,(seesection7.7,Fig.7.8).Aswillbeexplainedinsection8.4.8,whenawheelloadisappliedonasleeper,thesleeperunderloadsupports40%oftheappliedload(against50%ofoldertheories).Thus,beneaththesleeper,40%oftheappliedloadwillbetransmitted,(146).Accordingly,stressesarereducedby1,000to5,000timesbetweenthepointwherethewheelloadisappliedandthesubgrade,(Fig.7.3).Inthisanalysis,dynamiceffects(seesection8.7)havenotbeentakenintoaccount,(152).

Fig.7.3.Thebasearea(A)ofeachcomponentofthetracksystemandthedistributionoftrainload,(150)

7.3.Trackonballastoronconcreteslab

Thetrackusuallyliesonballast,inwhichcasewehaveaflexiblesupportoraballastedtrack,(Fig.7.4.a).However,itispossiblethatthetrackliesonaconcreteslab,insteadofballast,inwhichcasewehaveaninflexiblesupportorslabtrack,(Fig.7.4.b).Althoughaslabtrackisusedincertainrailways(e.g.extensivelyintheJapaneseandtheGermanrailways,amongothers),itismosteffectivewhenusedintunnels,becauseitallowsasmallercross-sectionandfacilitatesmaintenance.Inmostofthetracksworldwide,aballastedtrackisstillthecase,asitensuresflexibility(animportantfactorintheeventofdifferentialsettlements)andmuchlowerconstructioncost,whileatthesametimeofferingaverysatisfactorytransverseresistance,evenathighspeeds,(148),(151),(153).Theproblemofnoise,whichismuchgreaterwiththetrackonconcreteslabthanwiththetrackonballast,shouldnotbedisregarded.Whenaslabtrackisapplied(e.g.inthecaseofatunnel),thesuddenvariationintrackstiffness(feltbypassengersasajolt)islessenedbyplacingrubberpadsofasuitablethicknessalongthetunnelentranceandexit.

Thechoicebetweenballastedandnon-ballastedtrackshouldbedoneinrelationtoconstructioncost(muchgreaterfornon-ballastedtrack),maintenancecost(muchgreaterforballastedtrack),technicalrequirements(bothsolutionshaveadvantagesanddisadvantages),takingintoaccounttheleveloftechnologicalperformanceandlaborcostforeachcase,(139).Slabtrackisexaminedinmoredetailinchapter17.

Fig.7.4.Ballastedtrackandslabtrack

7.4.Trackgauge

Thetrackgaugeisdefinedasthedistancebetweentheinnersidesoftheheadsofthetworails,measured14mmbelowtherollingsurface,(Fig.7.5).Trackswithdifferentgaugevalueshavebeenlaid,asfollows:Standardgauge,e=1.435m.Mostlinesallovertheworldhavebeenlaidatthisstandardgauge,whichhasbeenfoundtooptimizerollingstockdimensions.Metricgauge,e=1.000more=1.067m.Inmostcases,secondarylinesarelaidusingthemetricgauge.However,metricgaugelinesinsomerailways(Japan,India,SouthAfrica,Australia,NewZealand,SouthAmericaandothers)operateasprincipallinesatspeedsupto160km/handcansupportaxleloadsupto16÷18t,(138),(140).

Fig.7.5.Trackgauge(caseofastandardgaugetrack)

Broadgauge,e=1.520mor1.524m(Russia),e=1.668m(Spain),e=1.676m(India),e=1.600m(Ireland)andelsewhere.Theyhavebeenconstructedsoastobedifferentiatedfromthestandardgauge,mainlyforpoliticalreasons,topreventstandardgaugerailvehiclesfromtrespassingintobroadgaugetracks.Narrowgauge,e=0.914more=0.760m.

ItshouldbenotedthatgaugevalueshadinitiallybeenexpressedinBritishmeasurementunits(inches),hencethegeneralirregularityoftheabovenumericalvaluesbytheirconversionintometricunits.

Inatotalof1,028,723kmsofrailwaylinesworldwide,57.5%arelaidonthestandardgauge,26.5%onthebroadgauge,15.5%onthemetricgaugeand0.5%onthenarrowgauge.

OncurveswitharadiusR<400m,extensionsaregiventotrackgauge,upto20mmforstandardgaugetracksontimberorsteelsleepers,upto10mmfortracksontwin-blockreinforced-concretesleepersandupto5mmfortracksonmonoblockprestressed-concretesleepers.Formetricgaugetracks,extensionsoftrackgaugearegivenforradiusR<500mandcantakevaluesupto20mm,(136),(140).

Smalltolerancesmaybeacceptedbetweennominalvaluesoftrackgaugeandactualvaluesandaredetailedintherelevantspecifications.

7.5.Axleloadandtrafficload

7.5.1.Axleload

Theaxleloadandthetrafficload(tonnage)runningonthelinearecriticalfactorsfortrackandsubgradefatigue.Permittedvaluesofaxleloaddependprincipallyontrackequipmentandmoreparticularlyonrail,sleeperandballastcharacteristics.Dependingontrackequipment,differentvaluesofaxleloadmaybeapplied.Forstandardgaugetracks,axleloadshavebeenstandardizedandclassifiedbyUICintofourcategories:

A:Maximumaxleload16t,B:Maximumaxleload18t,C:Maximumaxleload20t,D:Maximumaxleload22.5t.

CategoryDwasderivedbyincreasingtheaxleloadofcategoryCfrom20tto22.5t,inanefforttoreducetheoperatingcost,especiallyforfreighttraffic.Thisincreasewasmadeafteryearsofresearchandstudies,(145),withcontroversywhichdidnotfocusasmuchontrackstrengthasonthebehaviorofbridgeswhichhadbeendesignedfora20taxleloadonthebasisofsimplifiedtheoriesofelasticbehavior.Researchontheelastoplasticbehaviorofmaterials,(seesection8.4.4),hasshownthatbridgesdesignedforaxleloadsof20tcanwithstandaxleloadsof22.5twithouttheneedforstrengthening,duetostrengthreserveswhichtheelastictheorycouldnottakeintoaccount,(145).

Railwayaxleloadsforstandardgaugetrackswereonly10tin1850andprogressivelyincreasedto12tin1880,14tin1900,20tin1930and22.5tin1980.

Certainrailwayswithstandardgaugetracks,however,uselargeraxleloads.IntheUSA(whererailwaysaremainlyfocusedonfreighttransport)themaximumaxleloadforstandardgaugetracksis25÷32t.

Axleloadsforbroadgaugetracks(Russia,Spain,etc.)is25t.Formetricgaugetracksaxleloadsareupto14÷16t(somemetricgaugetrackscansupportaxleloadsupto18÷20t),(136),(140).

AseriesofresearchhasshownthatrailfatigueisanexponentialfunctionoftheaxleloadQ,andstressesdevelopedwithintherailareproportionaltotheparameterQa,wheretheexponentatakesvaluesintherangeof3to4andcloserto4,(152).Thus,anyincreaseintheaxleloadresultsinamuchlargerincreaseintrackmaterialfatigue.

7.5.2.Trafficload

Onatrack,variouskindsofrailvehiclesarerunning:passengervehicles,freightvehicles,locomotives.Thealgebraicsumofthevehicleloadscannotgiveanaccuratequantificationoftherunningload,becauseitdoesnottakeintoaccountthewayinwhichtheloadisapplied,therunningspeed,etc.Therefore,aparametergivinganaccurateestimateofthepassingtrafficloadisnecessary.Railwayengineeringusestheanalogueofthepassengervehicleunit(PVU)oftrafficengineering.Inordertodeterminethetrafficload(ortonnage)onatrack,theloadsofthevarioustrainsarefirstconvertedintoequivalentpassengertrainloadsandthenspeedsarealsotakenintoaccount.

Forthispurpose,acompositetrafficvalueiscalculated,takingintoaccountboththeeffectsofspeedandtherelativewearprovokedbyaxleloads.LineclassificationhasbeenstandardizedbytheUIC(Regulation714R)andisdeterminedonthebasisofatheoreticaltrafficloadTthgivenbythefollowingformula,(143):

Tth=Sp·(Tp+kt·Tpt)+Sfr·(kfr·Tfr+kt·Ttf)(7.1)

where:Tp:themeandailypassengertonnagehauled(ingrosstons),Tfr:themeandailyfreighttonnagehauled(ingrosstons),Ttp:themeandailytonnageoflocomotivesusedinpassengertraffic(intons),Ttf:themeandailytonnageoflocomotivesusedinfreighttraffic(intons),kfr:acoefficienttakingintoaccounteffectsofboththeloadandwearprovokedbyfreightbogiesandisgiven,(143):

normallythevaluekfr=1.15,however,fortrackshandlingheavyloads,coefficientkfrisgiventhefollowinggreatervalues:

–kfr=1.30fortrafficbasedprincipallyon20taxleloads(morethan50%oftraffic)orforasignificantproportionoftrafficwith22.5taxleloads(morethan25%oftraffic),

–kfr=1.45fortrafficbasedprincipallyon22.5taxleloads(morethan50%oftraffic)orfortrafficlargelyconsistingof20torheavieraxleloads(morethan75%oftraffic),

kt:acoefficientwhichallowstotakeintoaccountwearresultingfrom

tractionlocomotives.Thecoefficientktisusuallygiventhevaluekt=1.40,

SpandSfr:coefficientsrelatedtotherunningspeedofthetrain.Moreparticularly,SprelatestothespeedofthefastestpassengertrainsandSfrrelatestothespeedofordinaryfreighttrains.Thesecoefficientsareassignedthefollowingvalues,(143):

Sp,Sfr=1.00forV<60km/h,=1.05for60km/h<V<80km/h,=1.15for80km/h<V<100km/h,=1.25for100km/h<V<130km/h,=1.35for130km/h<V<160km/h,=1.40for160km/h<V<200km/h,=1.45for200km/h<V<250km/h,=1.50forV>250km/h.

Basedonthedailytrafficload,thevariousrailwaylinesareclassified,accordingtotheUIC(Code714R),into6groups(theformerclassificationuntil1989included9groups)asfollows,(143),(Fig.7.6):

group1forTf>130,000tons/day,group2for80,000tons/day<Tf<130,000tons/day,group3for40,000tons/day<Tf<80,000tons/day,group4for20,000tons/day<Tf<40,000tons/day,group5for5,000tons/day<Tf<20,000tons/day,group6forTf<5,000tons/day

Fig.7.6.ClassificationofrailwaylinesintoUICgroupsaccordingtothedailytrafficload,(143)

7.6.Sleeperspacing

Thestudyoftrackbehaviorhasshownthat,thecloserthesleepersarespaced,

thebettertheloaddistributionandthesmallerthestressesdeveloped.Assleeperspacingismadesmaller,however,trackmaintenancebecomesmoredifficult.Acompromiseshouldthereforebefoundbetweentheabovetworequirements.

Sleeperspacingisdefinedasthedistancebetweentheaxesofconsecutivesleepers,anditsoptimumvalueforstandardgaugetracksis0.60m,whichcanbereducedto0.55mincasesofsubgradeinadequacyandsmallradiusofcurvature.Acceptedtolerancesofsleeperspacingduringconstructionofthetrackare±0.02m.Occasionallythenumberofsleepersperkilometerisusedasaparameter,with1,666sleepersperkilometeroftrackastheaveragevalue.Inrailwayswithhighervaluesofaxleload(e.g.,theUSA),sleeperspacingmaybereducedto0.50m.Onlightweightrailways,sleeperspacingmaybeincreased,butrailfatiguemustbecarefullyconsidered.

7.7.Thewheel-railcontact

Afundamentalcharacteristicofrailvehiclesisthatthewheelmovementisguidedbythetworails.Wheel-railcontact,(Fig.7.7),hasanellipticalform,(Fig.7.8).Therailaxisinclinationtotheverticalistermedconicaltreadγandhasthevalue1/20(e.g.,Frenchrailways)or1/40(e.g.,Germanrailways,Japanesehigh-speedtracks),(149).

Wheelmovementontherailgivesrisetothecreepeffect.Indeed,thewheel-railcontactsurfacecanbedividedintotwoareas,S1andS2,thesizesofwhichdependonthevehiclespeed,(147).Thus,thevehiclerollingresistanceconsistsoftwocomponents,F1andF2,correspondingtoareasS1andS2respectivelyandofoppositedirection.ForceF1isgeneratedbyvehiclemovement,(i.e.itisofkinematicorigin),whileforceF2isgeneratedbyelasticdeformationoftheS2surface,(i.e.itisofelasticorigin).

Fig.7.7.Thewheel-railcontact

Fig.7.8.Detailofthewheel-railcontactsurface

Asspeedincreases,S1becomeslargerandS2smaller.Athighspeeds,S2almostdecreasestozero.

Abetterapproximationofthephysicalphenomenabetweenwheelandrailconsidersthattheellipticalcontactsurfacemaybedividedintotwosections,(154):ThefirstsectionofthecontactsurfaceundergoescreepingandeachpointofthefirstsectiontransmitstothesecondsectionofthecontactsurfaceatransverseforcegivenbyCoulomb’sequation.ThesecondsectionofthecontactsurfacetransmitstothefirstoneaforcewithavaluelowerthanthatgivenbyCoulomb’sequation.

Moreaccurateandanalyticalmethods,suchasthefiniteelementmethod,permittostudymoreindetailphenomenainthewheel-railcontactsurface,(133).

Railwaysinmostcasesusemetalwheels.Rubberwheelsstartedbeingusedafter1970inmetropolitanrailwaysandtramwaystoreducevibrationstransmittedtotheenvironmentandincreaseaccelerationanddeceleration.Rubberwheelsdonotpermitincreasedspeedsandaresubjecttodeteriorationunderbadweatherconditions.Forthisreasontheyareusedprincipallyinmetrovehicles.

7.8.Transversewheeloscillationsalongtherail

Fig.7.9.Simulationofarailvehiclebyasolidcomposedoftwocones

Arailvehiclecanbesimulatedbyasolidcomposedoftwoconesconnectedattheirbaseandsupportedbythetworails,(Fig.7.9).Thewheelconicaltreadγhasavalueof1/20or1/40.

Duetotheconicaltread,thewheelfollowsasinuouspathalongtherail,(Fig.7.10).

Fig.7.10.Pathofthewheelsalongthetrack

Thegapbetweentherailheadandthewheelallowsthelattertomovetransversely,afactthatcausesthesinuousmovementoftherailvehicle.Transversewheelmovementsareopposedbycreepforces.

Analysisoftransversemovementsofarailvehiclecanbedonebyassumingasinusoidaltransversemovementwithnoattenuation.Let,(Fig.7.11),(147):

y:thetransversemovementfromequilibriumposition,v:thetrainspeed,s:thetrackgauge,γ:thewheelconicaltread,R:theradiusofcurvatureofthesinusoidalmovement,

r:thewheelradius,x:theabscissa.

Fig.7.11.Analysisoftransversewheelmovement

FromFigure7.11andthesimilartrianglerelationship,itfollowsthat:

TherelationshipbetweenyandRiddeducedfromkinematicsasfollows:

Fromequations(7.7)and(7.8)wededucethedifferentialequationforthesinusoidalwheelmovement:

Giventhelimitcondition

y(0)=0(7.10)

thesolutionforthedifferentialequationbecomes:

withy0theamplitudeandLthewavelength,

Themaximumvalueofthetransverseaccelerationis:

Asanumericalexample,letr=0.45m,s=1.435m,γ=1/20,inwhichcaseL=15.96m.If,however,γ=1/40,thenL=22.57m.

Thefrequencyofthesinusoidalwheelmovementcanbefoundfromtheequation:

Whenfrequencyfisthesameasthefrequencyatwhichtherollingstockresonates,thenwheelmovementbecomesinstable.Thetransverseacceleration,whichisameasureoftheforcesexerted,showstheopposingeffectsgeneratedbyincreasingthespeedanddecreasingthetransversemovementwavelength.Aconicaltreadof1/40insteadof1/20isthereforemoreadvantageousconcerningwheelmovementatthesamespeed.Conversely,asthewheelsgraduallywearoff,conicaltreadincreasesandasaresultwavelengthdecreases.

However,inmodernrailvehiclestherollingstockbodyisnotsupporteddirectlybythewheelaxlesbutbybogies,whichareinturnsupportedbytheaxles.Therefore,themovementofrollingstockonbogiesisclearlymorecomplexthandescribedabove.Therelatedanalysisisgiveninsection19.4.

7.9.Railinclinationonsleeper

Fig.7.12.Railinclinationonsleeper

Duetotheconicaltread,railsaremountedonsleepersataninclination.Asexplainedpreviously,theconicaltreadisgiveninsomerailwaysthevalue1/20.Areductionofthevalueoftheconicaltreadhasbeensuggested,however,

especiallyathighspeeds.Severalrailwaysarealreadymountingtherailsonthesleepersataninclinationof1/40,(149).AccordingtotheEuropeantechnicalspecificationsforinteroperability,railinclinationonthesleepershouldbeintherange1/20÷1/40,(134).

7.10.Loadinggauge

7.10.1.Staticanddynamicloadinggauge

Theloadinggaugeisdefinedastheminimumexternalborderrequiredtoremainfreearoundtherollingstock.Theloadinggaugeisdistinguishedin:staticloadinggauge,whichistheminimumexternalborderrequiredtoremainfreewhilethetrainisnotmoving.Itshouldtakeintoaccountallobstaclestructures,suchaspowersupplyandsignalingequipmentalongthetrack,dynamic(calledalsokinematic)loadinggauge,whichistheminimumexternalborderrequiredtoremainfree,whilethetrainismoving.Theboundaryenclosingtheclearspacesrequiredaroundthedynamicloadinggaugeisthestructuregauge.Thedifferencebetweenthestructuregaugeandtheloadinggaugeiscalledtheclearanceanddependsonthespeedofthetrainandwhetherthetrackisonastraightlineoracurve.Theloadinggaugemainlydependsontwoparameters:–therollingstockwidth(usuallybetween2.60÷3.30m),–thespacingbbetweentheaxesofthetwotracks(usuallybetween3.60÷4.80m).

7.10.2.European,BritishandAmericanloadinggauge

TheInternationalUnionofRailwayshasspecifiedtheloadinggauge,whichisrequiredtoensurethattrainsfromonenetworkcanrunonothernetworktrackswithoutanyproblems,(Fig.7.13).ThedistancebbetweentheaxesofthetwotracksvaryforspeedsV<200km/hbetween3.57mand3.67mforFrenchrailwaysandbetween3.75mand4mforGermanrailways,(142).EvenwiththeUICstandardization,however,significantdifferencesintheloadinggaugeareobservedforstandardgaugetracks,mainlyintheUnitedKingdom,(Fig.7.14),whereloadinggaugehassmallerdimensionsthanincontinentalEurope,(141).Americanloadinggauge(Fig.7.15)alsohassignificantgeometricaldifferencescomparedtotheEuropeanones,(136).

Fig.7.13.Medium-andlow-speedloadinggauge,(136)

Fig.7.14.Britishloadinggauge,(141)

Fig.7.15.Americanloadinggauge,(147)

7.10.3.Loadinggaugeforhigh-speedtracks

Theloadinggaugeisdifferentforhigh-speedtracks,mainlybecauseofthelargespacingbnecessarybetweentheaxesofthetwotracks,aswellasthelargelateraldistances.Thus,forhigh-speedtracks,thedistancebis:•b=4.20minthecaseofFrenchrailways,withVmax:300km/h(lineParis-Lyons),•b=4.70minthecaseofGermanrailways,withVmax:300km/h.AreasonofthisgreatervalueofbinGermanrailways,istheexistenceofmanytunnels,

•b=4.30minthecaseofJapaneserailways,withVmax:320km/h,•b=4.80minthecaseofFrenchrailways,withVmax:350km/h(lineLyons-Marseille),

•b=4.00minthecaseofItalianrailways,withVmax:250km/h.AccordingtotheEuropeantechnicalspecificationsforinteroperability,the

minimumdistancebetweentheaxesoftrackseitherspecificallybuiltorupgradedforhighspeedsshouldbe4.00÷4.50m,(Table7.1),(134).

Table7.1Minimumdistancebetweentrackaxesforhigh-speedtracksaccordingto

theEuropeantechnicalspecificationsforinteroperability,(134)

7.10.4.Loadinggaugeformetrosystems

Thedynamicloadinggaugerequiresspecialattentionwhentrainsarerunningthroughtunnels,aswellasinthecaseofmetropolitanrailways,(Fig.7.16).Eachrailwayandmetroauthoritymusthaveitsownlocalstructuregaugerequirements,whichmustbefollowedineachspecificcase.

Fig.7.16.Dynamicandstaticloadinggaugeofametro(withnarrowrollingstock)oncurvedtrack,(144)

7.10.5.Loadinggaugeformetricgaugetracks

Figure7.17illustratestherollingstockoutlinesforsomemetricgaugerailwaysandthesuggestedrollingstockoutline,(140).Itisrecommendedthatwhenfixedstructuresarebeinginstalled,theyshouldbe250mmoutsidetheextremeofalloftherollingstockgaugesillustratedinFigure7.17.

Concerningdynamicloadinggauge,itshouldallowalateralmovementofthevehicleof±43mmandarotationofthevehicleof±2.00degreesaroundarollcenterthatissituated330mmabovetheraillevel,(138).

7.11.Forcesgeneratedbythemovementofarailvehicle-Staticanddynamicanalysis

7.11.1.Forcesgenerated

Forcesexertedonthetrackduringtherunningofarailvehiclemaybeclassified,dependingontheirdirection,asfollows:

Fig.7.17.Rollingstockoutlineforvariousmetricgaugerailwaysallovertheworld,(140)

–Verticalforces,whicharetheprincipalcauseofthemechanicalstressesinthetrack.Whensubjectedtoverticalforces,thebehaviorofcertainpartsofthetrack(rails,sleepers)iselastic,whilethatoftheballastandthesubgradeiselastoplastic,(148).Verticalforcesarecriticaltothedimensioningofthevariouscomponentsofthetracksystem.

–Transverseforces,whichinfluencetrainsafetyandmay,undercertain

conditions,causetrainderailment.Theeffectsoftransverseforcesareanalyzedinchapter13.

–Longitudinalforces,whichmayhaveasorigin:brakingoraccelerationoftherailvehicle,changesinthelengthofcontinuousweldedrails,duetotemperaturechanges.Theproblemisdiscussedindetailinsection10.13,creepofthetrack,(seesection11.9.5).

Althoughanaccurateanalysisofthevariousphenomenahasshownanon-linearbehavior,theinaccuracyintroducedbytheomissionofthenon-linearityisoftensmallerthantheinaccuracyintroducedbyotherparameters,e.g.thevaluesofthemechanicalcharacteristics,(148),(152).Itiscommonpracticeinrailwayengineeringtoanalyzeseparatelytheeffectsofvertical,transverseandlongitudinalphenomena,generatedduringtrainmotion,andthensumupthevaluesofstressesandsettlementscalculatedseparately.Suchanapproachiscalledsuperposition,whichhoweverimpliesthatthephenomenastudiedareassumedtobelinear.Itisanapproximation,whichtheengineermustbeawareofintheanalysisofthevariouseffects.Theprincipleofsuperpositioncanbewrittenas:

f(a+b)=f(a)+f(b)(7.15)

whereftheeffectanda,bexternalforces.

7.11.2.Staticanddynamicanalysis-Trackdefectsandadditionaldynamicloads

Afrequentassumptioninrailwayengineeringisthatboththewheelandtherailarefreeofdefectsandthatmetal-to-metalcontactofwheeltorailissmooth.Measurementsofthestresseshavefurthermoreshownthattheinfluenceoftimemaybeconsideredasnegligibleinmostcases.Insuchconditions,astaticanalysisofthevariouseffectsisadequate,(137).

Inboththewheelandtherail,however,defectsdooccur,(seesection16.4),causingadditionaldynamicloadstothewheel–railsystem.Theseadditionaldynamicloadsincreaserapidlyastrainspeedincreases.Forcemeasurementshaveshownthatforwheelloadsof10tand200km/hspeeds,theadditionaldynamicloadsmayattainvaluesupto4÷6tons,(152).Therefore,ifatlowspeedstheadditionaldynamicloadscanbeneglected,thisisnotsoatmediumspeedsandevenlesssoathighspeeds(seealsosections8.5and8.6).

Duetotheirrandomnature,anaccurateanalysisoftheadditionaldynamic

loadsispossiblebyspectralanalysis,(135).Withthismethoditwasfoundthatadditionaldynamicloadscanbeclassifiedintotwogroups:•Additionaldynamicloadscausedbysprungmasses(rollingstock)andinfluencedbythetypeandthecharacteristicsoftherollingstock,(Fig.7.18).Oscillationsofsprungmassesincreasewithtrainspeed,butatalowerrate.Theincreaseoftheoscillationsofthesprungmassesisafunctionoftheirverticaloscillationresonancefrequency,(152).

•Additionaldynamicloadscausedbyunsprungmasses(wheels,rails,sleepers),whichareproportionalto:speed,themagnitudeoftrackdefects,thesquarerootoftheunsprungmassesandthesquarerootoftheverticalstiffnessofthetrack.ThestandarddeviationoftheadditionaldynamicloadsΔQcausedbytheunsprungmassesmaybeexpressedbytherelation,(132),(152):

Figure7.18.Sprungandunsprungmassesinarailsystem

where:sdΔQ:standarddeviationofΔQ,V:railvehiclespeed,m:unsprungmassperwheel,h:verticalstiffnessofthetrack,whichasexplainedinsection8.2.2,

isdefinedash=Q/z,withQthewheelloadandztheverticalsettlementattheraillevel,

a:dampingfactor,A:empiricalcoefficientdependingontrackmaintenanceconditions.

7.12.Influenceofforcesonpassengercomfort

Passengercomfortisaffectedbothbythevaluesofverticalandtransverseaccelerationsexertedonthehumanbody,butalsobythefrequencyofvibration.Itwasfoundthatcomfortisminimumatfrequenciesintheorderof5Hz,andthatthehumanbodysupportsmoreeasilyvibrationscorrespondingtofrequencies5÷20Hz,(147).

8MechanicalBehaviorofTrack

8.1.Avarietyofmethodsadjustedtothenatureoftheproblemunderstudy

Anaccurateknowledgeofthemechanicalbehavioroftrack(stress,strain,moments,etc.)isessentialforarationaldimensioningofthevariouscomponentsofthetracksystem,whichshouldsatisfyrequirementsforbothsafetyandeconomy.

Thereisavarietyofmethodswhichcanbeadjustedtothenatureoftheproblemunderstudy.SomemethodsarebasedonBoussinesq’sanalysis(multilayersystemwithelasticbehavior),orconsiderthetracksystemasauni-directionalproblem.Moremodernmethodsusefiniteelementanalysis,whichpermitstherealgeometryandtherealstress-strainrelationtakingintoaccount.Forsomeproblems,boundaryelementmethodsmayalsobeused.Theproblemsoccurringincontactsurfaces(rail-sleeper,sleeper-ballast,etc.)maybeapproachedbyunilateralcontacttheories,which,however,untilnowhavefailedtogiveaccuratenumericalresults.

Inmostcases,satisfactoryresultscanbedrawnfromastaticanalysis,thatiswithouttakingintoaccounteffectsoftime.However,thereareproblems,suchastheanalysisofgroundvibrationsfromrailtraffic,forwhichadynamicanalysis,takingintoaccounttheeffectoftime,isnecessary.

8.2.TrackcoefficientsandBousinesq’sanalysis

8.2.1.Definitions–Symbols

Wewillfirstexamineastaticapproachofthemechanicalbehaviorofthetrack.Let,(Fig.8.1):Q:wheelload,z:verticalsettlementattheraillevel,r:wheelloaduniformlydistributedalongtherail,R:verticalreactionbetweensleeper-rail

l:sleeperspacing,S:sleepingseatingarea,p:averagepressureappliedatthesleeperseatingsurfaceontheballast.

Fig.8.1.Simplifiedapproachofthetracksystem

8.2.2.Trackcoefficients

Wedefinethefollowingtrackcoefficients,(147):

Substitutingequation(8.1)in(8.3),weobtain

andsinceR=ℓ·r(equilibrium’sequation),then

Theballastcoefficientisdefinedas

Substitutingequation(8.3)in(8.6)weobtain

andsince ,wewillhave

Ingeneralterms,thereactioncoefficientofacomponentofthetracksystem

isdefinedaswhereznistheverticalsettlementattheleveloftheexaminedcomponent.Hence,

Equation(8.10)givesthetotalreactioncoefficientofthetrack-subgrademultilayersystem.

Belowaregivenvaluesofthereactioncoefficientρforthevarioustrackcomponents,(152):Rail5,000÷10,000t/mm

Timbersleeper50÷80t/mmConcretesleeper1,200÷1,500t/mmBallast10÷30t/mmRubberpad10÷20t/mm

Trackelasticitydependsonelasticcharacteristics,andthethicknessoftheballast,thesubgradeandtheelasticpadsbetweentherailandthesleeper.Itwasfoundthatalongexistingtrackswithonlyaballastlayer(i.e.withnosubballastlayer),thetotalreactioncoefficientrangesbetween0.15and1.0t/mm,with0.3t/mmasanaveragevalue,(152).

Subgradeelasticitydependsonsoilquality,withthefollowingreactioncoefficientvalues,(152):Siltysubgrade0.5÷1.5t/mm

Claysubgrade1.5÷2t/mmGravelorrockysubgrade2÷8t/mmFrozensubgrade8÷10t/mm

Incivilengineeringstructures(bridges,etc.),thereactioncoefficientvaluesrangefrom10to15t/mm,andthereforeelasticityisfarlowerthaninaconventionaltrack.Therubberpadsusedinthesecasesaresignificantlythicker.

8.2.3.TrackcoefficientsandBousinesq’sanalysis

Anincreaseinthethicknessofballastlayerwillresultinlowerstressesinthesubgradeandincreasedelasticityoftrack.Let:

e:thicknessoftheballastlayerρo:trackreactioncoefficientfore=0

ApplyingBoussinesq’sanalysis(multilayersystemwithelasticbehavior),thevaluesillustratedinTable8.1canbederived,(152).

Adetailedanalysisoftheinfluenceofballastthicknessontrackandsubgradestressandstrainisgiveninsection8.4.7.

Table8.1.Influenceofballastthicknessontrackelasticityandonthereductionof

subgradestresswiththeuseofBousinesq’sanalysis,(152)

8.3.Approximateuni-directionalelasticanalysisofverticaleffects

8.3.1.Assumptionsandformulas

Weconsiderthetrackasauni-directionalsystem,thattherailisofinfinitelength*andliesonahorizontalelasticlayerwithtrackindexk,(Fig.8.2).ThewheelloadissimulatedbyaconcentratedloadQ.ThisanalysisisnamedafterZimmerman,(178).Thefollowingsymbolswillbeused:M:bendingmoment,

T:shearforce,k:trackindex,E:modulusofelasticityofrail,I:momentofinertiaofrail.

Fig.8.2.Uni-directionalsimulationoftrack(railofinfinitelengthonelasticlayer)andmomentsinanelementarysectionABCD

Wewillstartwithequationsofstrengthofmaterials:

whereδ(x)istheDiracfunction,theFouriertransformofwhichisequaltoone,and:

Theequationoftheelasticlineis:

Bysubstitutingequations(8.11)and(8.12)in(8.14),itcanbederivedthat:

LetZ(ω)betheFouriertransform*ofz,andlet

Equation(8.15)istransformedas

and

ApplyingtheinverseFouriertransform,itisderivedthat:

for

and

Therefore,theanalyticalexpressionsofthebendingmoment,theshearforceandtheballastreactionwillbe:

8.3.2.Resultsofthemethod

ThegraphicrepresentationsofbendingmomentM,shearforceTandverticalsettlementz,(Fig.8.3),aresinusoidaldampedcurveswithawavelength

λof:Theamplitudeofthevariouscurvesisdecreasingbyadampingfactorequal

toe-π=0.0432betweenconsecutivewaves.Figure8.3showsthatforx>5·λ/8thebendingmomentMandtheshearforce

Tarepracticallyzero.TheinfluenceofthewheelloadQisthereforenegligible,accordingtouni-directionalanalysis,beyondthedistance5·λ/8fromthepointofapplicationoftheloadQ(around4m),whichhoweverisnotverifiedneitherby

moreaccuratetheoriesnorbymeasurements.

Fig.8.3.Bendingmoment,shearforceandsettlementofthetracksysteminrelationtodistancefromthepointofapplicationofthewheelload,accordingtouni-directionalelastictheory,(178)

ThemaximumvaluesofM,R,z,hare:

Equations(8.26)to(8.29)showthatifthesleeperreactioncoefficientρincreases,M0andz0decreaseandR0increases.Theverticalsettlementz0,however,whichisproportionalto1/ρ3/4decreasesmuchfasterthanthebendingmomentM,whichisproportionalto1/ρ1/4.Therefore,ahighvalueofthesleeperreactioncoefficientisbeneficialfortrackgeometry.Itshouldbenotedthatthesleeperreactioncoefficientismainlyaffectedbythequalityofthesubgrade,

wheremostofthetotalverticalsettlementoccurs.AnincreaseofsleeperspacingℓresultsinanincreaseofM,Randz.

However,verticalsettlementandsleeperreactionincreasefasterthanmoment,sincetheformerisproportionaltoℓ3/4,whilethemomentisproportionaltoℓ1/4.Consequently,areductionofsleeperspacingaffectstrackgeometrymoreandrailmechanicalbehaviorless.

WhenrailstiffnessE·Iincreases,M0increasesandz0andR0decrease.Railstiffnessincreasesmainlyasaresultofanincreaseofrailweightperunitlength.

Fromstrengthofmaterials,railbendingstressescanbecalculatedfromtheequation:

andconsideringthevalueymax,weobtain:

wherey0isthemaximumdistancefromtherailcenterofgravity.Therefore,anincreaseoftherailmomentofinertiainfluencessignificantly

thestressesgeneratedwithintherailandtoalesserdegreethetrackgeometry.Thisiswhytheincreaseoftheaxleloadinrecentyearshasledtoaconsiderableincreaseintherailcross-section.

8.4.Accurateanalysisofthemechanicalbehavioroftrack–Finiteelementmethodandelastoplasticanalysis

8.4.1.Ashortdescriptionofapplicationsofthefiniteelementmethodintrackproblems

Simplifiedmethods(Zimmermann’smethod,Boussinesq’smultilayermethod,etc.)permitanapproximatecalculationofstressandstrainquiteeasily.However,comparingtheresultsofsimplifiedmethodswithactualvalues,asmeasuredbyon-sitemeasurements,mayreachdifferencesasmuchas100%,(148).Suchagapbetweencalculatedandmeasuredvaluescannotbeeasilyaccepted.Itisthereforenecessaryforthemechanicalbehaviorofthetrack-subgradesystem(mainlycalculationsofthestrainandstressesdeveloped,onwhichthedimensioningofthevariouslayerswillbebased)tobeanalyzedby

moreaccuratemethods.Thisisnowrelativelyeasy,withthehelpofnumericalmethodsandpowerfulcomputers.Anaccurateanalysisofthemechanicalbehavioroftrackcanbeachievedwithapplicationsofthefiniteelementmethod.Inthismethod,insteadofthephysicalsystem,(Fig.8.4.a),asystemresultingfromdividingthephysicalsystemintodiscreteparts(finiteelements)isanalyzed,(Fig.8.4.b),(157),(164),(165),(172).

Fig.8.4.Therailwaysystem(a)andthemesh(constitutedoffiniteelements)ofthemodel(b),(164),(165)

Figure8.5illustratesthevariousstages(whichareanalyzedindetailinthefollowingparagraphs)forapplicationofthefiniteelementmethodinrailwayproblems.

Thefiniteelementmethodpermitstostudytheactualphysicalsystemwithoutextremesimplifications,takingintoaccountaccuratelimitconditions(i.e.theconditionsimpartingtostressesorstrainsspecificvaluesatlimitpositions,forinstance,inthesupportsdisplacementiszero)andtheaccurateconstitutivelawofbehavior(i.e.therelationbetweenstressandstrainforeverymaterial),(164),(174).

8.4.2.Constructionofthemeshofthemodel

Forreasonsofsymmetry(alongthelongitudinalandthetransverseaxes),thestudyoftheproblemcanbelimitedto¼oftheinitialsystem,(Fig.8.4.b).Theconstructionofthemeshofthemodelisanessentialpartofthemethodandtheresultingfiniteelementsmustbehomogeneous(i.e.ofaboutthesamesize),otherwisethemethodmaynotconverge,(168).

Fig.8.5.Successivestagesfortheapplicationofthefiniteelementmethodinrailwayproblems

8.4.3.Limitconditions

Thelimitconditionsconsideredareasfollows:conditionsofsymmetry,i.e.transversedisplacementatanyplaneofsymmetryiszero, conditionsatthemostdistantpointsoftheproblem,whereverticaldisplacementtotheplaneconsideredissettozero.Limitconditionsmustbesetinsuchawaythatthefiniteelementmodelwill

haveasimilarbehaviortothephysicalsysteminvestigated.

8.4.4.Stress-strainrelation

Theconstitutivelawofbehavior(stress-strainrelation)mustexpresstherealmechanicalbehaviorofthematerials.Concerningballastandsubgrade,itwasfoundthatthedeformationcausedbypassingloadsoftrainsconsistsoftwocomponents:–anelasticcomponentwhichdisappearsafterthepassageofthe

train,–aplasticcomponentremainingafterthetrainhaspassed,(146).

8.4.4.1.Caseofballastandsubgrade

Thebehaviorofballast,subballastandsubgrade,astestedbyinsituexperiments,(166),isfoundtobeelastoplasticandisgivenbythefollowingequations,(165):

where: :totaldeformation, :elasticdeformation,

:plasticdeformation,E:modulusofelasticity,v:Poisson’sratio,I1=σ11+σ22σ33,δij:Kronecker’sdelta,δij=1fori=j,δij=0fori≠j,f:plasticitycriterion,withadifferentformulaforeachmaterial,λ:ascalarquantity.Theindicesi,jtakethevalues1,2,3.

IthasbeenproventhattheplasticitycriterionbestsuitedforsoilmaterialsandballastistheDrucker-Pragercriterion,definedbytheequation,(167),(169):

where:

Ifthetrackbedisaconcreteslab,theplasticitycriterionisbestrepresentedbytheparaboliccriterion,expressedbytheformula,(169):

whereRc:compressivestrength,RT:tensilestrength.

8.4.4.2.Caseofrailandsleeper

Incontrasttoballastandsubgrade,railsandsleepershaveanalmostelasticbehavior,i.e.plasticdeformationsarenegligibleandneednotbetakenintoaccount.Wheneverplasticityeffectshavetobeconsidered,however,theparaboliccriterionshouldbeusedastheplasticitycriterionforconcretesleepers.Forrails,thevonMisescriterionshouldbeused,whichisgivenbytheequation,

(169):whereq:shearyieldstressofrail.

8.4.5.Numericalcalculations

Infiniteelementanalysis,threecategoriesofmodelshavebeendeveloped,(169),(177):–Strain(orkinematic)models,inwhichthelimitconditionsconcerningstrain(deformations)areintroducedasgivendata,whileequilibriumequationsaswellaslimitconditionsconcerningstressesaretheobjectofsuccessivenumericalcalculations.Strainmodelshaveprovenmoreconvenientbothinbeingconstructedandbeingimplemented.

–Stress(orstatic)models,inwhichequilibriumequationsandlimitconditionsconcerningstressesareintroducedasknowndata,whiledeformationsarecalculatedthroughsuccessivesteps.

–Hybridmodels,inwhichastrainmodelisappliedinageometricpartofthemodelandastressmodelinanotherpart.

Instrainmodels,inparticular,staticfiniteelementanalysisleadstothesolutionofthesystem

where:[K]:thesystem’sstiffnessmatrix,[q]:thedisplacementvectorofthesystem’snodes,[F]:thevectoroftheforcesexertedonsystem’snodes.

Thequantities[K],[q],[F]fortheentiresystemaretheresultoftheassemblyoftheelementaryquantities[Ke],[qe],[Fe]correspondingtoeachfiniteelement,(168),(177).

Theelastoplasticconstitutivelaw,correlatingstressandstrain,maybeimplementednumericallybytwomethods,(169),(177):a.Theinitialstressmethod,whichisslowerinconvergencebuteasiertouse,(Fig.8.6.a).b.Thevariablestiffnessmethod,whichhasthedisadvantagethatthestiffnessmatrixchangesateachsuccessivestep,(Fig.8.6.b).

Fig.8.6.Theinitialstress(a)andvariablestiffness(b)methodstoimplementtheelastoplasticstress-strainrelation,(169),(177)

8.4.6.Determinationofthemechanicalcharacteristicsofthevariousmaterials

Thesubgradecanbeofdifferentclasses(S1,S2,S3,R),(seesection9.5).Table8.2givestheaveragevaluesofthemechanicalcharacteristicsoftrackmaterials,asdeterminedbyaseriesoftestsconductedwithintheframeworkoftheInternationalUnionofRailways,(166),(175).Inotherfiniteelementmethodanalysesofthetracksystem,conductedseparately,similarvaluesofthemechanicalcharacteristicsoftrackmaterialswereintroduced,(157),(172).

Table8.2.Valuesofthemechanicalcharacteristicsofrailwaytrackandsubgrade

materials,(166),(175)

8.4.7.Stressandstraininthetrack-subgradesystem

Finiteelementanalysisallowsallparametersofthetrack-subgradesystemtobetakenintoconsideration,(146),(164),(165): subgradesoilquality(S1,S2,S3,R),(seesection9.5), sleepertype(seesections11.3,11.5,11.6):–twin-blockreinforced-concretesleeper,–monoblockprestressed-concretesleeper,–timbersleeper,trackbedthicknesse(=ballast+subballast).

Figures8.7,8.8,8.9illustratetheverticalstressesatthesubgradelevel,aswellastheverticalsettlementsattherail,sleeperandsubgradelevel,accordingtotheelastoplasticanalysisbythefiniteelementmethod,(146),(164).Itcanbededucedthatthevaluesofstressesareprimarilyaffectedbythesubgradesoilqualityandtoalesserdegreebythetrackbedthicknesse.Indeed,thebetterthesubgradesoilqualityis,thelessertheinfluenceofthicknesse.Inparticularandwithallotherparametersunchanged,animprovementofsubgradequalityfromoneclasstothenext(S1→S2,S2→S3,S3→R)willresultinanincreaseofthestressesdevelopedinthesubgradebyabout50%.

Fig.8.7.Verticalstressesatthesubgradelevelforvarioussubgradeandsleepertypes,asafunctionoftrackbedthicknesse(=ballast+subballast).Elastoplasticfiniteelementanalysis,(146),(164)

Fig.8.8.Verticalsettlementsatthesubgradeandsleeperlevelforvarioussubgradeandsleepertypes,asafunctionoftrackbedthicknesse(=ballast+subballast).Elastoplasticfiniteelementanalysis,(146),(164)

Fig.8.9.Verticalsettlementsatthesleeperandraillevelforvarioussubgradeandsleepertypes,asafunctionoftrackbedthicknesse(=ballast+subballast).Elastolasticfiniteelementanalysis,(146),(164)

Withrespecttotheinfluenceofthesleepertype,itcanbededuced(exceptinthecaseofarockysubgrade)thattimbersleepersandmonoblockprestressed-concretesleepershaveabetterloaddistribution,i.e.theyresultinsmallervaluesofstressesinthesubgrade.Inanycase,theinfluenceofsleepertypeissmallerthantheinfluenceofsubgradequality.

8.4.8.Distributionofwheelloadalongsuccessivesleepers

Railwayengineershavebeenaccustomed,onthebasisofsimplifiedconsiderations,totheassumptionthatwhenawheelloadisappliedaboveasleeper,thenthesleeperbelowtheloadsupports50%ofthewheelloadandeachoftheneighboringsleeperssupportsanother25%.Stressmeasurementsandfiniteelementanalysisapplications,however,haveshownthatwheelloaddistributionalongsuccessivesleepersisasfollows,(Fig.8.10),(146):–sleeperunderwheelload:40%,–firstneighboringsleeper:23%,–secondneighboringsleeper:7%.

Therefore,whenawheelloadisappliedoverasleeper,itseffectisnegligible

beyondthesecondsuccessivesleeper.Theaboveloaddistribution,inconjunctionwiththevalueofthewheelload,affectssleeperdimensioning.

Fig.8.10.Wheelloaddistributionalongsuccessivesleepers,(146).

8.4.9.Elasticlineofsleeper

Theelasticlineisanessentialpartofthemechanicalbehavioroftherailwaysystem.Figure8.11illustratesacomparisonoftheelasticlinefortimberandmonoblockprestressed-concretesleepers.Figure8.12illustratestheelasticlineofatimbersleeperforvariousqualitiesofsubgrade,(146).Thesignificantroleofthesubgradeisagainconfirmed.

8.5.Dynamicanalysisofthetrack-subgradesystem

Asdiscussedinsection7.11.2,anadequatecalculationofthestressandstrainofthetrack-subgradesystemmaybeobtainedbystaticanalysis,thusneglectingdynamiceffects.Acomparisonoftheresultsoffiniteelementstaticanalyseswithstressandstrainmeasurementshasshowndeviationsnotexceeding20%,thusconfirmingthatthestaticapproachcanbeconsideredassatisfactoryforstressandstrainanalysis,(165).

Fig.8.11.Comparativeelasticlinefortimbersleeperandmonoblockprestressed-concretesleeper,(146)

Fig.8.12.Elasticlineoftimbersleeperforvarioussubgradequalities,(146)

Therearephenomena,however,whichcannotbeadequatelysimulatedbythestaticapproach.Theseincludetheproblemofthetransmissionofvibrationsfromthetrainstotheenvironment,theproblemofthemotionandthesuspensionofthevariousrollingstockcomponents,etc.,(158),(170).

AsatisfactorysimulationofdynamiceffectscanberealizedbyaviscoelasticconstitutivelawandisillustratedinFigure8.13,where: thesymbolrepresentselasticbehavior, thesymbol representsviscousbehavior, thesymbol representsviscoelasticbehavior(Kelvin-Voigtmodel), railvehiclesandbogiesaremodelledasnon-deformablesolids, wheelsandsleepersaremodelledasdiscretemasses, theballastandthevarioussubgradelayersaremodelledashorizontallayers, thevarioussystemcomponentsareinterconnectedbyaviscoelasticstress-strainrelation.

Fig.8.13.Modellingofthevehicle–track–subgradesystemforadynamicanalysis,(148)

Inthedynamicanalysis,theproblemisreducibletosolvingthedynamic

equation:

where:[M]:themassmatrix,[C]:theviscosity(damping)matrix,[K]:thestiffnessmatrix,[q]:thedisplacementvector,[ ]:thevelocityvector,[ ]:theaccelerationvector,[F]:theexternalforcesvector,[R]:thevectorofthereactionsexertedbythesleepersontheballast.

Inthedynamicanalysis,thecalculationsaremorecomplexcomparedtothestaticoneandthereforetakealongertime.Forthisreason,theyshouldberestrictedonlytophenomena,whichcannotbeadequatelysimulatedbystaticanalysis,(156),(165).

8.6.Trackdefectsandadditionaldynamicloads

Analysesofthemechanicalbehavioroftherailsystemhaveuntilnowbeenbasedontheassumptionthatbothrailsandwheelsaresmoothandfreeofdefects.However,thisisnotthecase,andasexplainedinsection7.11.2,defectsthatappearstimulatethesystemandcauseadditionaldynamicloadsQdyn,whichmayreachvaluesofupto50%ofthewheelload.

Themechanicalanalysisofthetrack-subgradesystemshouldthereforebeconsiderednotonthebasisofthestaticwheelloadQstat,butbytakingintoaccountthetotalload,(Fig.8.14):Qtot=Qstat+Qdyn(8.44)

Fig.8.14.Trackdefectsandadditionaldynamicloads

Additionaldynamicloadsmaybedividedintothreecategoriesaccordingto

therespectivevibrationfrequency:–Loadsintherange0.5Hz<ν<15Hz.Thesecorrespondtothemovementofsprungmasses(rollingstock),(seesection7.11.2)anddependprincipallyonthecharacteristicsandpeculiaritiesoftherollingstock.

–Loadsintherange20Hz<ν<100Hz.Thesecorrespondtothemovementofunsprungmasses(wheels,rails,sleepers),(seesection7.11.2)anddependmainlyontrackqualityandstiffness.

–Loadsintherange100Hz<ν<2,000Hz.Thesecorrespondtoshort-andlong-pitchcorrugationsoftherailsurface,(seealsosection10.9.4.4).Ifweassumealinearbehavior,thenitispossibletoseparateeachclassof

additionaldynamicloads(correspondingtoaspecificrangeoffrequencies)fromothers.InordertocorrelateaccuratelyandcausallytrackdefectsandtheresultingdynamicloadsQdyn,spectralanalysisisused,sincetrackdefectsmayberecordedaccuratelyandindetailbyspecialrecordingvehicles.Thisanalysisisagainbasedonthedynamicequation(8.43).

8.7.Dynamicimpactfactorcoefficient

Thedesignoftrackcomponentsisusuallyconductedwiththehelpofstaticanalysis.Thequestionarises,however,whatisthedynamicimpactfactorηbywhichthestaticloadshouldbemultipliedinordertotakeintoaccountinthestaticanalysisthedynamiceffects.Figure8.15summarizestheresultsofvarioustheories.

Figure8.15illustratesdifferencesbetweenidealtracktheoreticalcalculation(curve7)andmeasuredvalues(curve6)orvaluessuggestedbyvariousempiricalformulas(curves1÷5).However,curves1÷3arededucedfromoldrollingstockcharacteristicsandarenotvalidformodernrollingstock.Moreclosetorealityarecurves4,5,6,whichillustratethatforthespeed200km/hthedynamicimpactfactorηvariesfrom1.35to1.6.Thus,forspeedsapproaching200km/hadynamicimpactfactorof1.5issuggested.Forspeedsgreaterthan200km/hananalyticalsurveyshouldbeconductedbasedonexperimentaldata.

Fig.8.15.Resultsforthedynamicimpactfactorηaccordingtovarioustheories,(163)

Legend

ValuesmeasuredonvehiclesoftheFrenchhigh-speedTGV001(1981)Valuesoftheoreticalcalculationforidealtrackandvehiclecontactsurfaces

withoutanyirregularities

8.8.Designofthetrack-subgradesystem

Thedesignofthetrack-subgradesystemshouldtakeintoaccountthefollowingtwoprinciples,(146),(164):–loadsmustbeproperlydistributedtothevariouslayers,sothatdevelopedstressesinthesubgrademustbelessthanthevaluescausingfailure

–adequateflexibilityofthesystemshouldbeensured,i.e.trackstiffnessshouldnotbeexcessive.Trackstiffnessismainlydeterminedbysubgradesoilqualityandtrackbedthickness.Rockysubgrades,forinstance(withnoproblemasregardsproperdistributionoftrainloads),havestiffnessmorethantriplethatofclaysubgrades.Accordingly,rockysubgrades,althoughfreeofloaddistributionproblems,mustalwayshaveaballast+subballastlayer,(155),(158).

Figure8.16illustratestheaveragecontributionofeachcomponentofthetracksystemtothetotalelasticityofthetrackinthecasesoftimberandconcretesleepers,(158).

Figure8.16.Contributionofeachcomponentofthetracksystemtothetotalelasticityoftrack,(158)

8.9.Vibrationsandnoisefromrailtraffic

8.9.1.Originsofrailvibrations

Arailvibratingsourceproducesthreetypesofwaves,(160),(171):compressionwaves(7%oftheenergytransmitted),whicharelongitudinalwaveswithparticlemotionbeinganoscillationinthedirectionofpropagation, shearwaves(26%oftheenergytransmitted),withparticlemotionbeinganoscillationinaplanenormaltothedirectionofpropagation,Rayleighwaves(67%oftheenergytransmitted),whicharesurfacewaves,withaparticlemotionellipticalinaverticalplanethroughthedirectionofpropagation.Railvibrationshaveinlowspeedstwoprincipalorigins:

–enginesofrollingstock,–wheel-railinteraction.

Inelectrifiedlines,athirdoriginshouldbeadded,thecatenarynoise,causedbyfrictionfromtheslidingcontactofthepantographalongthetrolleywire.Afourthnoiseoriginisofaerodynamicnature.Noiseofaerodynamicorigincanbeconsideredasminorforlowandmediumspeeds(V<200km/h),asimportantforhighspeeds(200<V<300km/h)andasprevailinginveryhighspeeds(V>300km/h).

8.9.2.Relationofrailnoiseleveltospeed

Fromvariousanalyses,itisfoundthatthereisalogarithmicrelationbetweenthelevelofrailnoiseL(indB(A)*)andtrainspeedV,oftheform,(160),(163):L(dB(A))=a+b·logV(8.46)withcoefficientsa,bdependingontherollingstockandthetrackcharacteristics,typeoftraffic,soilcharacteristics,etc.

8.9.3.Dampingofrailnoiseinrelationtodistance

Figure8.17illustratesthenoiselevel(indB(A))invariousdistances(100m,300m,400m)fromthetrackandforspeedsfrom130km/hto200km/h.Wecannotethat:–thenoiseleveldoesnotdecreaselinearlyforeachdoublingofdistanceaswouldbeexpected,probablyduetogroundimpedance,–noiselevelsareinfluencedmorebydistancethanbychangesinspeed,–noiselevelsarecorrelatedwiththelogarithmofspeed.

Fig.8.17.Railnoiselevelinrelationtodistanceandspeed,(163)

8.9.4.Noiselevelinrelationtoinfrastructuretype

Measurementsofnoiselevelat25mfromthetrackcenterlinehavebeenconductedataspeedof200km/hintheJapaneseShinkansenhigh-speedtrain(with12÷16vehicles)forvariousinfrastructuretypes:bridge,viaduct,embankmentandcut,(Fig.8.18).

Fig.8.18.Noiselevelinrelationtoinfrastructuretype,(163)

Thenoiselevelsincutsubgradesshowtheeffectivenessofthissolutioninreducingthenoisefromrailtraffic.Consequently,geometricaldesignandchoice,whereverpossible,ofcutsectionsinlayoutcanbeusedasawaytoreducetheimpactanddisturbancesfromrailvibrationsandnoise.

8.9.5.Noiselevelsinhighspeeds

Amajorconcerninhigh-speedtrainsistoreducethenoiselevelsemitted.Thusanoiselevelof97dB(A)isreportedfortheFrenchTGVat25mfromthetrackandaspeedof272km/h.FortheGermanICE,noiselevelsof86and93dB(A)havebeenreportedatadistanceof25mfromthetrackforspeedsof200and300km/hrespectively,(162).Table8.3illustratesnoiselevelsinrelationtothetypeofthetrainanddistance.

Table8.3.

NoiselevelsindB(A)inrelationtothetypeoftrainanddistance,(162)

8.9.6.Noiselevelstandards

Ifnoiselevelcannotbereducedotherwise(e.g.bytheappropriatedesignofrollingstockandtrack),theusualmeans(inordertocomplywithnoiselevelstandards)istoconstructnoisebarriersalongthetrack,soastoprotectneighboringsensitivehumanactivities.

Inrecentyears,nationalandinternationalspecificationsrequirestudiesofenvironmentaleffectsincasesofimportantprojects,suchasnewrailwaylines.Standardsfornoiseleveldifferfromonecountrytoanother,(seealsosection22.3).

8.10.Analysisoftheaccuratemechanicalbehaviorofrail

Amodelfortheanalysisofthemechanicalbehaviorofrailcanbeasfollows,(Fig.8.18),(159):–railisrepresentedbytheso-calledbeamofThimosenko(linearbeamsubmittedtoverticalandtransversebendingandtorsion),–supportofrailtosleeperismodelledbysprings,–ballastandsubgradearerepresentedbythree-dimensionalfiniteelements,–twowheelloadsareappliedsymmetrically,(Fig.8.19).

Figure8.20illustratestheresultsofthemodelconcerningverticalsettlementsoftherailalongthelongitudinalaxisandFigure8.21illustratessettlementsofrailinrelationtotime(t=0.0,applicationofwheelload).

Fig.8.19.Amodelfortheanalysisofthemechanicalbehaviorofrail,(159)

Fig.8.20.Verticalsettlementsofrailalongthelongitudinalaxis,(159)

Fig.8.21.Verticalsettlementsofrailinrelationtotime,(159)

8.11.Applicationofunilateralcontacttheoriesinrailwayproblems

8.11.1.Transmissionofforcesthroughcontactsurfaces

Therailwaysystemisbasedonthetransmissionofforcesthroughcontactsurfaces:wheel-rail,rail-sleeper,sleeper-ballastorsleeper-slabtrack,ballast-subballast,subballast-subgrade.Contactsurfacesareusuallysupposedtobecontinuousandperfect,ahypothesis,however,whichiscontradictedbyphysicalobservations.Unilateralcontacttheoriespermitcalculationnotonlyofstressandstrainfieldsbutalsooftheaccuratecontactsurfacesbetweentwosolids,(137).

8.11.2.Unilateralcontacttheories

Letusconsiderthecontactbetweenrailandsleeper,(Fig.8.22),whichisperfectinapartΓ0,whereasinanotherpartΓ2thereisnocontact.Weassumethatthesupportofrailtosleeperismodelledbyspringsofarigidityk.Calculationofstress,strain,surfaceΓ0,surfaceΓ2isbasedontheassumptionofSignorini:wherecontactisperfect,workofexternalforcesiszero;wherethereisnocontact,workofexternalforcesisnegative,(161).

Fig.8.22.Rail-sleepercontact

8.11.3.Equationsoftheunilateralcontactproblem

Weassumeanelasticandstaticbehavior.Then:

8.11.4.Numericalcalculations

Ultimately,theproblemisreducibletotheminimizationofthedynamicenergyofafieldkinematicallyacceptable,(161).Inpracticethismeansthatduringsuccessiveiterations,ifaspringofthemodelledsystemissubjectedtotension,itisremovedandthusconditionsofnocontactarecreated.Ifaspringissubjectedtocompression,thenthereisaperfectcontact.

Theunilateralcontacttheories,describedabove,permittheaccuratecalculationofcontactsurfacesofrailway(andmoregenerallyengineering)problems.However,tothisdate(2013)noaccuratenumericalapplicationofthesetheoriesinrailwayproblemshasbeenreported.

*Thisassumptionisveryclosetopracticewithcontinuousweldedrails,seesection10.13.*TheFouriertransformFfofafunctionf(x)isdefinedbythefollowingrelation:

*AmongthefiniteelementsoftwarewecanmentionSofistik,Adina,Abacus,Cosmos,etc.

*Theaccurateplasticitylawiswrittenas

Ifdeformationsaresmall,thislawcanbesimplifiedas

*Decibel(dB)isaunittomeasurethelevelofnoiseandreferstothepressurereceivedbythehumanear.Amongthevariousmethodsofsimulationofrailnoise(whichiscomposedofsoundsofmanyfrequenciesandintensities),themostcommonlyusedismethodA,whichemphasizesonfrequenciesaround2,000HzandtheresultingmonitoringofnoiseisexpressedasdB(A).

9Subgrade–GeotechnicalandHydrogeologicalAnalysis

9.1.Theimportanceoftherailwaysubgradeontrackqualityanditsfunctions

Railwaysubgradeisparticularlyimportantinensuringthattrackqualityreachesthestandardnecessaryforthesafeandcomfortableoperationoftrains.Railwayauthoritiesmakeseriouseffortstoimprovepassengercomfort.Theseefforts,however,concentrateusuallyontracksuperstructure(rails,sleepers,ballast,subballast)(seeFigure7.1)andoftendisregardthefactthatmanyproblemsappearingatthetracksuperstructurelevelaretraceabletothesubgrade,ratherthantothesuperstructure.

Itshouldbestressedthat,inthepast,studiesconcerningtherailwaysubgradewereinfluencedbyideasprevailinginhighwayengineering.Thishadtheadvantageofusingthetechnicalexperiencesacquiredwithhighways,butthedisadvantage,whenhighwaydesignspecificationswereappliedliterally,thatthetechniquesimplementedwerenotcompatiblewiththepeculiaritiesoftherailwaysystem.

Therailwaysubgradeproblemarisesindifferentwaysinnewandexistingtracklayouts.Accordingly,innewlayoutsthesubgradedesignisafunctionoftrackloading(axleloadandtracktonnage),sleepertypeandballastthickness.Arationalconsiderationoftheproblemrequiresthatthevariousparametersdefiningthesubgradebetakenintoaccount:soiltype,hydrogeologicalconditionsandmechanicalstrengths.

Ontheotherhand,inexistinglayouts,theproblemisdifferent.Thepolicyoftherailwayauthoritiesforhigherspeedsandhigheraxleloadsleadstoincreasedsubgradestresses.Sinceinexistinglayouts,thelowersurfaceofthesubballastandtheuppersurfaceofthesubgradehaveformedacompactzone,whichshouldbedisturbedaslittleaspossible,thereisonlylimitedpossibilityofinterventioninthesubgrade.However,anyinterventioninthesubgradeshouldbelimitedtoareaswhereparticularproblemshavearisenandshouldbe

scheduledasmuchaspossibletobeperformedduringperiodictrackmaintenance.Thedecisionbetweenimprovingthesubgradeorincreasingtheballastlayerthicknessshouldbethesubjectofatechnicalandeconomicstudyandisthereforedifficulttomakeinadvance,(191).

Therailwaysubgradeshouldfulfillthefollowingfunctions:enablepassengerandfreighttrainstorunsafelyatthespecifiedspeed,supportaxleloadsoffreightandpassengertrains,minimizefuturetrackmaintenancecosts.

Thesefunctionscanbeachievedby:•limitingsettlementsoftheoriginalgroundandoftheembankmentfilling,•providingstablemechanicalbehaviorundertrainloadsandearthworks,•facilitatingaquickevacuationofrainandgroundwater,•ensuringthattheconditionofthesubgradedoesnotdeteriorateduringitsworkinglife.

9.2.Analyticalgeotechnicalstudy

9.2.1.Targetsofageotechnicalstudyandsoilinvestigation

Beforeconstructinganewrailwayline,ageotechnicalinvestigationshouldbeconducted.Nonewlinecanbeeitherdesignedcorrectlyorconstructedeconomically,unlessboththenatureofsoilsencounteredandthehydrogeologyoftherouteareknownindetail.

Ageotechnicalinvestigationshouldindicate:–whethermaterialforembankmentconstructionisavailableonsiteorwillhavetobetransported,

–theappropriateslopesforembankmentsandcuts,–whetherlooseningordensificationofsoilmaytakeplace,–whereweakgroundrequirestreatmentbeforefillingcancommence,–wheregroundwaterlevelsmaycauseproblems,–themeasuresnecessarytoensurethestabilityofearthworkslopesinthelongterm,

–wherecutsectionsrequireparticulardrainageorprotectivemeasures,–theappropriatetypeofplanttobeusedoncutorembankmentslopes.

Asageotechnicalinvestigationiscostly,itshouldbeconductedin

successivestageswiththeuseofthemostappropriatetechniques.

9.2.2.Preliminarystudies

Thefirststageofageotechnicalinvestigationisthestudyofavailabledocuments,suchas:topographicmaps,geologicalmaps,hydrogeologicaldata,aerialphotographs,historicalinvestigationrecordsrelatedtothearea,etc.,(186).Sitereconnaissanceshouldalsobeincludedatthisstage.

Thepreliminarygeotechnicalanalysisshouldpermitageneralunderstandingofthegeotechnicalproblemslikelytobeencounteredandprovideabasisforplanningthemaingeotechnicalstudy.

9.2.3.Techniquesandmethodsofexplorationusedinageotechnicalstudy

Ageotechnicalstudyisacomplexprocedurethatusesmanytechniques,suchas,(186):–Geophysicalmethods(seismic,magnetic,gravimetric,resistivity),–Physicalmethods(boreholes,trialpits),–Mechanicalmethods(pressuremeterorpenetrometer,laboratorytests),–Hydrogeologicalmethods(suchaspiezometers,etc.).

Themostwidelyusedmethodofgroundinvestigationisboringholesintotheground,fromwhichsamplesmaybecollectedforeithervisualinspectionorlaboratorytesting.Severalproceduresarecommonlyusedtodrilltheholesandtoobtainthesoilsamples.

Table9.1liststhewidevarietyofinsitutestscurrentlyavailable,(188).Priorto1960thislistwouldhaveincludedonlystandardpenetrationtest,mechanicalconetest,vanesheartestandplateloadtest.FromthelistpresentedinTable9.1,severalchoicesareprovidedinmakinganinsitudeterminationofanyofthenecessaryengineeringparameters,(184).

9.2.4.Planningtheexplorationprogram

Thepurposeoftheexplorationprogramistodeterminethestratificationandengineeringpropertiesofthesoilsunderlyingthesitewherearailwaytrackwillbeconstructed.Themainareasofstudyarestrength,deformationandhydrauliccharacteristics.Theprogramshouldbeplannedsothatthemaximumamountofinformationcanbeobtainedattheminimumcost.

Theplanningofagroundexplorationprogramincludessomeorallofthe

followingsteps:Assemblyofallavailableinformation.Reconnaissanceofthearea,whichincludesthefollowing:–geologicalmaps,–topographicmaps,

Table9.1.Insitusoiltestmethodsandtheirapplicability,(188)

–aerialphotographs,–waterand/oroilwelllogs,–hydrologicaldata,–soilmanualsbystateauthorities.

Apreliminarysiteinvestigation.Inthisphaseafewboringsaremadeoratestpitisopenedtoestablishinageneralmannerthestratification,thetypesofsoilstobeexpectedandthelocationofthegroundwatertable.Adetailedsiteinvestigation

9.2.5.Geotechnicalreportandlongitudinalsection

Theresultsofgeotechnicalinvestigationsaresummarizedinthegeotechnicalreportandthelongitudinalsection.Figure9.1illustratesthegeotechnicalcharacteristicsalongtheChannelTunnel,whichisconstructedalongalayerofbluechalkthatwasprovenresistanttowaterpenetration.

Fig.9.1.GeotechnicalcharacteristicsalongtheChannelTunnel

Thegeotechnicalreportshouldgiveclearandaccuraterecommendationsonthefollowingissues,(186):geotechnicaldescriptionofeachlayer,hydrogeologicaldata:maximumandminimumpiezometriclevels,drainagerequirements,methodsofconstruction,heightofearthworks,suitabilityofsoilsforre-use,valuesofrecommendedslopes,embankmentdesign,eventualspecialtechniquessuchasreinforcedsoil,etc.,calculationofmechanicalcharacteristicsofsoilsandofthebearingcapacityofthesubgrade.

9.3.Geotechnicalclassificationsofsoils

Inexistingrailwaylines,whichwereconstructedmanydecadesago,suchananalyticalgeotechnicalsurveyisnotnecessary.Nevertheless,ageneralknowledgeofthebasicparametersofthemechanicalbehaviorofthesubgradeisessential.Thevariousgeotechnicalclassifications,adoptedmainlyforhighwayengineeringprojects,areahelpfultoolforthispurpose.Theseclassificationsarebasedonthefollowingcharacteristics:granulometricgradingandAtterberglimits(liquiditylimit,plasticitylimit,shrinkagelimit).Occasionally,mechanicalparametersarealsotakenintoconsideration,suchastheCBRindex*,etc.

VariousrailwaynetworkswithinEuropeclassifiedsoilsinthepastinadifferentmanner,asillustratedinthecasesofthefollowingcountries,(191)(199):theUnitedKingdom,France,Germany,SwitzerlandandothersusetheUnifiedsoilclassificationsystem(USCS),alsoknownasCasagrandeclassification,Scandinaviancountriesmainlyrelyongranulometricgradingofthematerials,Italy,GreeceandothersusetheAASHO(Americanassociationofstatehighwayofficials)classification.Ofthese,theUnifiedsoilclassificationisthemostgenerallyapplicableand

mostwidelyused.ItwasdevelopedfromasystemproposedbyCasagrande(1948).Coarse-grainedsoils(sandsandgravels)areclassifiedaccordingtotheirgrading,whereasfine-grainedsoils(siltsandclays)andorganicsoilsareclassifiedaccordingtotheirplasticity.Classificationiscarriedoutusingparticlesizedistributiondataandvaluesoftheliquiditylimitandplasticityindex.

TheAmericanassociationfortestingandmaterials(ASTM)hasadoptedtheUnifiedsoilclassificationasabasisforitssoilclassification,entitled‘Standardtestmethodforclassificationofsoilsforengineeringpurposes’.ThelatterissomewhatdifferentfromthatoftheUnifiedsoilclassificationbutthemethodofclassificationisalmostidentical.ThemaindifferenceisthattheASTMclassificationrequiresclassificationteststobeperformed,whereastheUnifiedsoilclassificationallowsatentativeclassificationbasedonvisualinspectiononly;however,theASTMclassificationprovidesafurthersubdivisionofsoilclasses.

TheBritishstandardclassificationsystem(BS5930)is,liketheUnifiedsoilclassification,basedontheCasagrandeclassification,butthedefinitionsofsandandgravelaredifferent.

TheGermanclassification(DIN4022)ismoreanalyticalandproceedsforsilt,sandandclayatfurthersubdivisions(fine,medium,coarse).

Soilscomposedofmixturesoftwoormoregroupsoffine-grainsizesareusuallyconsideredseparately.Anaccurateclassificationofsuchsoilswithsimilargranulometriccompositionsrequiresthatplasticitycharacteristics(Casagrandediagram)bealsotakenintoconsideration.

Despitethesmalldifferencesofthevariousmethods,thefollowingclassificationiscommonlyacceptableinsoilmechanics,(Fig.9.2):•Rock:low-,medium-,orhigh-variabilityrock,dependingonthedecay-disintegrationithasundergone.

•Gravel(2÷4.76mm<d<20÷76.2mm):Well-orpoorly-gradedgravel,siltygravel,claygravel.

•Sand(0.02÷0.074mm<d<2÷4.76mm):siltysand,claysand.•Fine-grainedsoil(0.0001<d<0.05÷0.074mm):Slightlyplasticsilt,slightlyplasticclay,veryplasticsilt,veryplasticclay.

Fig.9.2.Varioussystemsofgeotechnicalclassificationofsoils

9.4.Hydrogeologicalconditions

Anotherfundamentalparameter,usedindeterminingthesubgradequality,ishydrogeologicalconditions.

Thevariousrailwayauthoritieshavetriedtodetermine,themaximumgroundwaterlevelbeyondwhichhydrogeologicalconditionsareconsideredtobebad.Figure9.3illustratestheminimumdistancesofthegroundwaterlevelfromacertainreferencelevel,forhydrogeologicalconditionstobeconsidered

good,accordingtotheregulationsofvariousrailwaynetworks,(186),(199),(200).

EvenifthegroundwaterlevelisbelowthatshowninFigure9.3,hydrogeologicalconditionsarenotgenerallyconsideredgoodifsuitabledrainagedevicesarenotprovided,(Fig.9.4),orthesubballastdoesnothavetherequiredtransverseslope(3÷5%),(186),(199).

Moreover,areaswithlargegroundwaterlevelfluctuationsovertimeshouldbethesubjectofaseparatestudy.Insuchcases,itisofinteresttoexamine,fromatechnicalandeconomicpointofview,thefeasibilityofinstallingasandfilterorageotextile,(seesection9.15).

Forcountriesexperiencingverycoldwinterswherefrostoccursfrequently,athirdparametertobetakenintoaccountinvolvesthesusceptibilityofthesubgradetothepenetrationoffrost,(201),(seesection9.11).

Fig.9.3.Minimumdistance(inmeters)ofthegroundwaterlevelfromacertainreferencelevel,soashydrogeologicalconditionsbeconsideredgood,accordingtotheregulationsofvariousrailwaynetworks

Fig.9.4.Drainagedevicesalongtherailwaysubgrade

9.5.Classificationoftherailwaysubgrade

InaccordancewiththeUICclassification,thebehaviorofthesubgrademaymacroscopicallybecharacterizedbyandclassifiedasfollows,(186):–Lowsettlementsandverygoodsupportoftrainloads.ThissubgradeishereafterdesignatedasS3.

–Mediumbehaviorinsettlementsandinsupportingtrainloads.ThissubgradeisdesignatedasS2.

–Largesettlementsandnon-satisfactorysupportoftrainloads.ThissubgradeisdesignatedasS1.

–Extensivesettlementsandaverybadperformanceinsupportingloads.ThequalityofsuchasubgradeisdesignatedasS0.

Totheaboveclassesofsubgradeshouldbeaddedthecaseofasubgradecomposedofrockofsatisfactorystrength.ThequalityofsuchsubgradeisdesignatedasR.However,morerecentUICclassificationsincludetheformerlydesignatedrocksubgrade(R)withinthesubgradeofgoodquality(S3).

Thecriteriafortheclassificationintooneoftheabovecategoriesaregeotechnicalcharacteristicsofthesoilandhydrogeologicalconditions.Therefore,accordingtotheUIC,(186),therailwaysubgradeclassificationisshowninTable9.2.Thereferenceparametersusedinthisclassificationincludethepercentageoffinegrains,plasticityindexPI*andtheLosAngelescoefficient(seesection12.4.2).

SoilsofcategoryS0areinprincipleunsuitableforsupportingtrackproperly

forthefollowingreasons:theysettleextensively,theyareinhomogeneous,theircharacteristicsmaychangeovertimeandallowpenetrationofballaststonesdeeplyintothesubgrade.Suchsoilsshouldbeavoidedwheneverpossiblewhenlayingoutthetrack,orreplacedbymoreappropriatesoilmaterial.Shouldthisproveimpossibleandthetrackhavetotraverseareaswithsuchunsuitablesoils,especiallyonhighearthbanks,theriskofsettlementsshouldbeconsideredcarefullyandsoilimprovementsolutionsshouldbeexaminedincombinationwiththeappropriateincreaseintheballastandsubballastthicknessandtheuseofgeotextiles,(190),(196),(197).

Table9.2.Classificationofsubgradequalityasafunctionofgeotechnical

characteristicsandhydrogeologicalconditions,(186)

9.6.Mechanicalcharacteristicsofthesubgrade

Theroleofthesubgradeistowithstandtrainloadswhichhavebeenadequatelyattenuatedbythevarioustrackcomponents.Inordertowithstandloadsproperly,thesubgradeshouldhavetherequiredmechanicalproperties.

OnthebasisofaseriesoftestsconductedwithintheORE*framework,(148),thelimitswithinwhichthemodulusofelasticityrangesweredetermined

foreachofthesubgradecategories,accordingtotheUICclassification(Fig.9.5).Forrockysoils,themodulusofelasticityvariesinaccordancewiththenatureoftherockmaterialandisintheorderof3·104kp/cm2(seesection8.4.6,table8.2).

Inadditiontothemodulusofelasticity,classificationofsubgraderequiresthedeterminationofitscapacitytowithstandtrainloads.Forthispurpose,theCBRindexmaybeused.Figure9.5illustratesvaluesofCBR,whichcorrespondtothevarioussubgradecategories,(186).

Fig.9.5.ModulusofelasticityandCBRindexforvarioussubgradecategories,(186)

9.7.Theformationlayer

9.7.1.Layingofformationlayerinnewtracks

IfthesubgradesubsoilisclassifiedasS1orS2,itisadvisabletoplaceanadditionaltoplayercomposedofabetterqualitysoilmaterial.Thislayerisoftentermedtheformationlayer.

Theformationlayershouldbemorecompactthanthesubsoil.Mostrailwaysrequiretheformationlayertohaveacoefficientof100%bytheStandardProctorCompactiontest,whilethisvalueisroutinely95%forsubsoillayersinthecaseofembankments,(151).

Useoftheformationlayerleadstoasubstantialimprovementinthesubgradebehavioronlyifthefollowingtworequirementsaremet,(151):thesubsoilofthesubgradehasalowwatercontent,otherwisegrainsofthesubsoilmaypenetratetheformationlayeranddeterioratethetransverseslope,theformationlayershouldbehomogeneousandfreeoflocalconcentrationsof

fine-grainedmaterial.Thethicknessoftheformationlayerisdefinedasafunctionofthesubgrade

quality.ValuesofTable9.3werefoundsemi-empirically,(186).

Table9.3.Requiredthicknessoftheformationlayerasafunctionofthequalityof

subsoilofthesubgradeforUIC1÷4grouplines,(186)

9.7.2.Improvementofformationlayerinexistingtracks

Manytrackshavebeenconstructedinthepastwithoutaformationlayer.Insomeoftheseoldtracks,itisnecessarytoincreasespeedandaxleload,whichresultinincreasedstressesinthesubgrade.Themostpracticalsolutionistoincrease,duringmaintenanceworks,thethicknessesoftrackbedstructures,which,however,willbedifficultincaseswheretheheightabovethetrackislimitedormaynotleadtothedesiredvaluesofstressesinthesubgrade.Insuchcases,itwillbenecessarytoimproveorinstallaformationlayerinanexistingtrack,whichisillustratedindetailinTable9.4,(189).

9.8.Impactoftrafficloadonthesubgrade

Whenstudyingtheimpactoftrafficload(linetonnage)andmaintenanceconditions,Dormon’srule,establishedforhighwayengineering,canbeusedwithanaccuracythatcanbeconsideredsufficient.AccordingtoDormon’srule,themechanicalstressesdevelopedinthesubgradeareinverselyproportionaltothenumberoftheloadingcycles,raisedtoapowerλ,(151):

whereσ1,σ2arethestressescorrespondingtoN1,N2loadingcycles,respectively,

andλisanexponentwithameanvalueof0.2,(151).

Table9.4.Variousmethodsforimprovingtheformationlayer,requiredequipmentandmachinery,workingconditionsandestimatedtimeforexecution,(189)

LetPbetheaxleloadandTthedailytrafficload(tonnage),(seesection7.5.2).Fromequation(9.1)itfollowsthat:

Inthecaseofaconstantaxleload,P1=P2,thentheequation(9.2)becomes

9.9.Impactofmaintenanceconditionsonthesubgrade

9.9.1.Themaintenancecoefficient

Inordertoestimatetheextent(andthereforetheexpense)oftrackmaintenance

works,themaintenancecoefficientkisusedasaparameter.Theentirerailwaynetworkisdividedintosectionswithapproximatelythesamenumberofmaintenancesessionsoftrackteamsalongeachsection,maintenancesessionsbeingunderstoodtomeanallsessions,witheithermanuallaboraloneorincludingtheuseofmechanicalequipment,betweentwocompleterenewalsofthetrack.LetIbetheannualnumberofworksessionsalongasectionandImtheaveragenumberofmaintenancesessionsalongtracksofthesameage(i.e.renewedinthesameyear),belongingtothesameUICgroupandcarryingtrainswiththesameaxleload.Themaintenancecoefficientkisdefinedas:

Thevaluek=1correspondstoanaveragemaintenancelevel,whereasthevaluek=0.5correspondstoasatisfactorymaintenancelevel.Itshouldbenotedthatwhensubgradequalityispoor,kmaytakevaluesupto10,(Fig.9.6).

9.9.2.Impactofthemaintenancecoefficientonthebehavioroftrackbedandthesubgrade

Useofthemaintenancecoefficientkmaycontributetoarationalplanningoftrackmaintenanceworks.Figure9.6illustratesmaintenanceexpenses(forUIC1÷3grouplines)asafunctionofthemaintenancecoefficientandthenumberofyearselapsedsincethelastcompleterenewal.Onthebasisofthepointonthecurvesbeyondwhichmaintenanceexpensesincreasedisproportionately,thetimeforthenextcompleterenewalofthetrackisrationallydetermined.

Fig.9.6.Maintenanceexpensesformanualworksessions(inman-hoursHperkmoftrack)andannualnumberofworkmaintenancesessionsI(bothwithmanualandmechanicalmeans)asafunctionofthemaintenancecoefficientkandthenumberNofyearssincethelastcompleterenewal.CaseofUICgroup1÷3lines

WhenindexI(seeFig.9.6)exceedsacertainthresholdvalue,trackgeometrystandardscannolongerbefullyensured.Itisthennecessarytocarryoutothermethodsoftrackimprovement,sincemaintenancehasreacheditslimitsofefficiency,soastotrytoreducethevalueofmaintenancecoefficientk.Suchareductionispossiblethroughanincreaseofthethicknessofthetrackbedlayers.

Basedonthevalueofthemaintenancecoefficientkwecanassesswhethertrackbedlayershavebeenproperlydimensionedornot,(Table9.5).

Table9.5.Assessmentoftheproperdimensioningoftrackbedstructuresinrelationto

themaintenancecoefficientk,(186)

9.9.3.Impactofthemaintenancecoefficientonsubgradestresses

Letusnowconsidertwotracks1and2withdifferentmaintenancecoefficientsk1andk2respectively.ApplicationoftheDormonrulegives:

whereτisthetrafficloadoneachtrackbetweentwoconsecutivemaintenancesessions.StatisticalanalysishasshownthatτisproportionaltothevalueofT/k,(151):

Consideringthecaseoftwotrackswiththesameaxleloadandthesametrafficload,equation(9.6)becomes:

Equation(9.7)allowscalculationoftheimpactofmaintenanceconditionsonthemechanicalstressesofthesubgrade.

Theuseofcoefficientkrequirestheaccuraterecordingofallmaintenanceproblemsandexpenses.

9.10.Fatiguebehaviorofthesubgrade

Fatigueisdefinedasthereductionofthemechanicalstrengthofamaterialundertheinfluenceofrepeatedloads.Inthecaseofmetals,ithasbeenfoundthatthereisalimitstressσ0(calledfatiguelimit),beyondwhich,ifexceededbythestressesdeveloped,fatigueeffectsoccurandmayleadtofailurewithoutbeingprecededbyanymacroscopicallylargedeformations,(seealsosection10.8).

However,forthesoilmaterialswhichconstitutethesubgrade,fatiguedoesnotinvolvethedevelopmentofexcessivestressesbutofplasticdeformationsinrelationtotheloadingcycles.Experimentalresultsofthetriaxialtestunderrepeatedloadingconditionsshowthattheparameter

hasalimitvalueintheorderof0.9,beyondwhichplasticdeformationsincreaseveryrapidly,asapparentfromFigure9.7.

Fortheevolutionofplasticdeformations asafunctionoftheloading

cyclesN,thefollowingrelationhasbeensuggested,(200):

wherea<b<…andtheparametersa,b,c,d,α,βaredeterminedexperimentally.Accordingtoequation(9.9),aslongastheexponentialtermsarenegligible,

plasticdeformationproceedslogarithmicallyandpracticallystabilizesafteracertainnumberofloadingcycles.Onthecontrary,iftheexponentialtermsofequation(9.9)haveadetermininginfluenceontotalplasticdeformation,thenthesubgrademayshowlargeanddangerouslyincreasingdeformationsasafunctionoftheloadingcycles.Suchbehaviorwasobserved,undercertainconditions,incasesofsubgradequalityclassifiedasS0orS1.

Fig.9.7.EvolutionofplasticdeformationsεpinclaysoilsasafunctionoftheparameterRandofthenumberNofloadingcycles

9.11.Frostprotectionofrailwaysubgrades

9.11.1.Frostindex

Railwayauthoritiesmustdecidewhethertheprotectionofthesubgradeagainstfrostshouldbecalculatedaccordingtothecoldestwinterpossible,orwhethertoinstallasubgradewhichwouldbesuitableforaveragewinters,whileacceptingthatfrostpenetrationwouldoccurinextremeconditions.

Frostindexisdefinedastheintegraloftemperaturewithrespecttotimeforallperiodswherethetemperatureisbelowzeroandisexpressedindegrees×hoursorindegrees×days.Table9.6givesthefrostindexinrelationtotheprobabilityoffreezingthroughaswellastheexpectedunderratingsdueto

frostpenetrationinacertainperiod,(198).Siltisverysusceptibletofrost,clayissusceptibletofrost,butsandandgravelarenotsusceptibletofrost.

9.11.2.Frostfoundationthickness

Alayerofmaterialorcombinationofmaterialsisplacedundertheballastlayer(orthesubballast)inordertoprotectthesubgradeagainstfrostheave.Frostfoundationisatermcomprisingseveralkindsoffrost-heavingpreventionmaterialsandmeasures.

Variousmaterials,suchasgravel,cinders,etc.,canbeusedinthefrostfoundationlayer.Figure9.8illustrates,inrelationtothefrostindex,theappropriatethicknessofthefrostfoundationlayerundertheballastandFigure9.9illustratestheappropriatethicknesswhenaninsulationlayeroffoamplasticisused.

Table9.6.Frostindex,probabilityoffreezingthroughandexpectednumberof

underratingsinacertainperiod,(198)

Fig.9.8.Thicknesszfroffrostfoundationlayerunderaballastlayerof35cm,(198)

Fig.9.9.Thicknesszfroffrostfoundationlayerunderaballastlayerof25cm,whenaninsulationlayeroffoamplasticisused,(198)

9.11.3.Frostprotectionmethodsonexistingtracks

Alongexistingrailwaytracks,whichcrossareasoftenfreezinginwinter,many

waysofimprovingthesubgrade(duringtrackrenewal)soastoprotectagainstfrosthavebeensuggested,(Figures9.10to9.13).

Fig.9.10.Frostfoundationofgravelorcinders

Fig.9.11.Frostfoundationofstonewithpeatfilter

Fig.9.12.Frostprotectionwiththeuseoffoamplastic

Fig.9.13.Combinationofinsulationandafroststoragebottomlayer

9.12.Tracksubgradeincutsandonembankments–Valuesofslopes

9.12.1.Subgradeincutsections

Beforeexcavatinganycutsection,particularattentionispaidtostudyingthegeologicalformationsinitspath(especiallyinthecaseofdiaclases),inordertodisturbthegeologicalformationequilibriumaslittleaspossible.Parameterstobeconsideredwhendesigningacutsectionincludesafety,cost,andadaptationtotheaestheticsofthesurroundingenvironment(andnottheotherwayaround).

Theslopesofthecutsectionsaredeterminedaccordingtotheresultsofthegeotechnicalstudy,withcommonlyusedvaluesasfollows,(184):

Protectionbytalusstabilizationisusuallyattainedbycoveringtheslopeswithshrubsorbyplantingtrees,thusatthesametimeachievingthemergingoftheworkswiththesurroundinglandscape.Grounddrainageisalsorequiredalongtheslopes,toavoidsoftening.

9.12.2.Subgradeonembankmentsections

Inthecaseofanembankment,thequalityofgeologicalformationsundertheembankmentshouldbealsoconsidered.Commonlyusedvaluesofslopesare,(184):

Ifthegroundslopeisgreaterthan1:10,itisadvisabletosecuretheembankmentbasebyusingastep-likeconfigurationasshowninFigure9.14.

Fig.9.14.Steppingofthebaseoftheembankmentinthecaseofsteepground

Duetothesubsequentcompactionoftheembankment,itsinitialdimensionsshouldbeaugmentedbothinwidthandinheight,(Fig.9.15).

Finally,inthecaseofverytallembankmentsides,aretainingwallorreinforcedsoil,designedtowithstandthesoilthrustandtrainloads,maybeused,(Fig.9.16).

Fig.9.15.Increaseoftheinitialwidthandheightofanembankment,duetotheexpectedreductioninsizebycompaction

Fig.9.16.Retainingwallinthecaseofverytallembankmentsides

9.13.Thereinforcedsoiltechnique

Reinforcedsoilisaflexibletechniquewhichcan,inmanyinstances,replaceretainingwalls.Reinforcedsoilisanassemblyconsistingof,(Fig.9.17):

theembankmentedge,goodqualitysoilmaterial,metallicbars,concretepanel.

Thereinforcedsoiltechniqueisespeciallyrecommendedformediumandpoorqualitysubgrades(S1,S0)andpermitsverysteepslopesandverticalwallstobesafelyconstructed.Particularattentionisrequiredinsecuringthemetalbarsthroughappropriateanchoringinthesoil.AcomparativeanalysisoftheconstructioncostforrailwayprojectsinFrance,(Fig.9.18),hasshownthatthereinforcedsoilsolutionisbotheconomicallyandtechnicallyadvantageouscomparedtotheconstructionofaretainingwall,especiallyforheightsbetween3mand12m,(193).Thereinforcedsoiltechnique,however,cannotbeusedinelectrifiedlines,sincetheelectriccurrentreturncorrodesthemetalbarsofreinforcedsoil,whichmayleadtofailure.

Fig.9.17.Thereinforcedsoiltechnique,(193)

Fig.9.18.ComparativeconstructioncostofretainingwallandofthereinforcedsoiltechniqueinrailwayprojectsinFrance,(193)

9.14.Hydraulicanalysisandcalculationofflows

9.14.1.Levelofgroundwater

Themechanicalbehaviorofthesubgradeandthestabilityofthetrackarestronglyaffectedbythelevelofgroundwater,whichshouldbeatleast80cmlowerthanthetoplevelofthesubgrade,(186).Ifthisisnotthecaseinsitu,thenthelevelofgroundwatermustbeloweredbyusingditchesordeepdrainagesystems,(195).

9.14.2.Semi-empiricalformulasforthecalculationofrun-offflows

Anyrainwaterlikelytopenetratetothesubgrademustbequicklyevacuated.Thetopsurfaceofthesubgradeshouldbegiventheappropriateslope(3÷5%)towardsdrainagedevices,whichmustbeusedbothtransversallyandlongitudinallyalongthetrack,(seeFig.9.4).

Thedesignofhydraulicdevicesisbasedonsemi-empiricalformulasofhydraulics,whichtrytocalculatethefollowingtworun-offflowsduringamajorstorm:a)run-offflowQpresultingfromthetrackwhichmaybeincutorembankmentandcanbecalculatedbytheformula:

where:i:slopeofthelongestflowpath,c:run-offcoefficientofthesubgrade,whichisequalto0.3or0.4fortheembankmentslopeand0.85forthetrack,A:surfaceofthecatchmentarea,

k,u,v,w:coefficientsdependingontheintensityofthestorm(10-year,50-year,100-year).

b)run-offflowresultingfromthecatchmentarea,whichiscalculatedinrelationtotheeffectivesurfaceAandtheaverageslopeiofthecatchmentareaandtheaveragerun-offcoefficientcofthecatchmentarea.Usualvaluesofcare:0.9÷1.1forimpermeablesurfaces,0.4÷0.8forcultivatedsoils,0.3forsandysoils,0.2forareaswithforests,(186).

Amongthevariousmethodsandformulas,itisworthmentioningthemethodoftheSoilconservationserviceofUSA,basedontheformulaofFuller,whichgivesthemaximumrun-offflowQmax:

where:Q1:maximumflow(inm3/sec)forareturnperiodofTyears,Q1=c·A0.8,c=1.8,A:thecatchmentarea(inkm2).

Asanexample,letusconsideracatchmentareaAof10km2andareturnperiodTof10years.Then:Q1=11.63m3/secandQmax=47.70m3/sec.IfA=15km2andT=20years,then:Q1=15.71m3/secandQmax=69.90m3/sec.

Aspreviousformulasaresemi-empirical,theyshouldbecheckedwithactualdata,otherwisetheycanleadtoerroneousestimations.Forinstance,whenstudyinghydraulicaspectsofthenewhigh-speedline‘TGVMéditerranée’,basedonrainfallmeasurementsandanalyticalformulas,themaximumflowfora100-yearperiodwasgivenvaluesof1÷5m3/sec/km2,whereastheobservedextremevaluesofwaterflowswerearound10m3/sec/km2.Forthisreason,analyticalmethodswereadaptedtoactualobservationsandtheminimaldiameterofhydraulicdevicesunderthetrackwas1.0m,(183).

9.14.3.Therationalmethodforthecalculationofrun-offflows

Anaccuratecalculationofrun-offflowsisfundamentaltothedesignofdrainagedevicesandfacilitiesforrailwayprojects.Eventualerrorsintheestimateswillresultinastructurethatiseitherundersizedandcausesseriousdrainageproblemsoroversizedandcostsmorethannecessary.Therelationshipbetweentheamountofprecipitationinadrainagebasinandtheamountofrun-offfromthebasiniscomplex,andbecomesevenmorecomplexinthechangingclimatesituationofourera.Experienceindicatesthatthedesignofdrainagedevicesshouldbebasedonadequatelydocumentedhydrologicanalysis.Semi-empiricalformulasofthepastdecadesshouldthereforebecomplementedwithrationalanalysis,whichispossibletodaywiththehelpofpowerfulcomputers,providedthatsufficientmeteorologicaldataareavailable.

Althoughinthepast,returnperiodsof50÷100yearswereconsideredtobesatisfactory,theincreaseofprecipitationintensity,asdocumentedbymanystudies,requireshigherreturnperiodsontheorderofevenupto1,000yearsandasabasicrun-offflowtheprobablemaximumflood.Variousmethodshavebeenpresentedtoconvertrainfalldataintoanestimateofpeakflow.Eachmethoddiffersincomplexity,datarequirements,andreliabilityofresults,aswellasitsuserexperienceneeds.Accordingtotherationalmethod,themaximumrun-offflowQpcanbecalculatedfromtheformula:

where:c:run-offcoefficient(dimensionless),I:rainfallintensity,A:thecatchmentarea(inkm2).

InEquation(9.12),therun-offcoefficientcistheleastprecisevariableanditsproperselectionrequiresjudgmentandexperienceonthepartofthe

hydrologistengineer.Thedatarequiredtoapplytherationalformulamaybeobtainedwiththeuseoftherun-offcurvenumberorwithcomputersimulations,suchastheHydrologicmodellingsystemsdevelopedbytheUSArmycorpsofengineers.

9.15.Geotextilesinrailwaysubgrades

9.15.1.Characteristics,typesandpropertiesofgeotextiles

Allrailwaysubgrades,butparticularlythoseofmedium,poor,orverypoorqualitycanbeimprovedthroughtheuseofgeotextiles.Geotextilesarepermeablegeomembranesconsistingofsyntheticpolypropyleneorpolyesterfibers.Theyare0.4÷3mmthickandareweighing70÷350g/moflength.Therearetwolargegeotextiletypes,(190),(197):wovengeotextiles,composedoftwointerwovenperpendicularfiberlayers.Theyarestronglyanisotropic,non-wovengeotextileswithisotropicbehavior;inthistypefibersarelaidrandomly.

Geotextileshavealargedeformabilityandareused:•toseparatetwoconsecutivelayersofgranularmaterials,•toreinforceasoillayerofinsufficientmechanicalstrength,•asfilters,•fordrainage.

9.15.2.Useandapplicationsofgeotextilesintherailwaysubgrade

Geotextilesareextensivelyusedinrailways.Theyarelaidunderthesubballast(neverundertheballast)andtheirpurposeismanifold,(196):i)Tofacilitateproperlayingofthetrackbedstructuresonthesubgrade.The

geotextilelaidontopofthesubgradepreventstheintrusionoffine-grainedelementsintothegravelsubballastandallowsasuitabletransverseslope(3÷5%)tobeimpartedtothesubgradesurface.Figure9.19illustratestheplasticitycharacteristicsofcertainclaysoils,inthecaseofwhichastronginfiltrationoffine-grainedmaterialsintothesuperposedgravellayerwasobserved,(201).

ii)Toincrease(underrepeatedloading)themechanicalresistanceofthetrackbedstructures.Useofgeotextiles,however,shouldnotentailanappreciable

reductionoftheballastandsubballastthickness,becausethiswouldresultinincreasedstressesofthesubgrade,(196).Geotextilescannotreplacetheballastandgravelindistributingverticalloads.Theapplication,bycertainrailways,ofgeotextileswithoutthelayingofsubballastinadditiontothereductionoftheballastthicknesshascausedfailures(perforationofthegeotextilebytheballast,ruiningofthetransverseslope,etc.).Thereinforcingeffectofgeotextilesmaybedeterminedbynumericalmethods,suchasfiniteelementanalysis,(185),(192),(194).Figure9.20illustratesthemeshofafiniteelementanalysisfortheassessmentoftheeffectsofuseofageotextileonthemechanicalstressesofthesubgrade.Thecaseofaslabtrackhasbeenstudiedandtwo-dimensionalanalysiswassatisfactory,(185).Ithasbeencalculatedthatuseofageotextileleadstoareductionofstressesontopofthesubgradebyaround10%,(185).

Fig.9.19.Thecombinationofplasticityindex(PI)andliquiditylimit(LL)atwhichastronginfiltrationoffine-grainedsubgradeelementsintothegravelsubballasthasbeenobserved,(201)

Fig.9.20.Meshofafiniteelementmodelfortheassessmentofthereinforcingeffectsofgeotextilesinrailwaysubgrades,(185)

iii)Theyfunctionasfiltersorasdrains.Inthiscase,thegeotextiletypeisselectedaccordingtotheformulas,(197):

where:kg:requiredgeotextilepermeability(cm/sec),tg:geotextilethickness(mm),ks:soilpermeability(cm/sec),d50:sievediameter(mm)allowingpassageof50%ofthesoilmaterial.

Geotextilescanalsoprotectthesubgradeagainstfrostintrusion.Beforeuse,itshouldbeascertainedthatthespecificgeotextilefulfillsthemechanicalstrengthrequirements:fracturestrength,elongationatfailure,perforationstrength,compressivestrength,waterpermeability,permeabilitytoinfiltrationoffine-grainedsoilmaterials,etc.Thevaluesofthesemechanicalpropertiesaredeterminedbyvarioustestsdescribedinrelatedmanuals,(190),(197).

Useofgeotextilesalongtherailwaysubgradeusuallyfulfillsalltheabove

purposes.Geotextiles,however,arecommonlyusedsimplytoseparatethegravelsubballastfromthesubgradesoilmaterial.

Whenevergeotextileshavebeenused,trackmaintenanceexpenseshavebeenreduced.Therefore,thegeotextileexpenseisamortizedveryquickly,(180).

9.16.Vegetationonthesubgradeandtheballast

9.16.1.Vegetationonthetrackandherbicides

Asthegreatmajorityofrailwaylinesarelaidinthecountryside,vegetationappearsonthesubgradeandtheballast.Railwaysmakeeffortstocontrolthisvegetationbyimplementingeithermechanicalorchemicalmeans(herbicides),thelatterbeingthemostefficientbutwithaharmfuleffectontheenvironment.Properdrainage,however,ofthesubballastlayerandwell-preparedsubgradeareimportantprerequisitesforcreatingconditionswhicharehostiletothegrowthofvegetation.

Sprayingofherbicidesonbothsidesofthetrackisconductedwiththeuseofspecialrailvehiclesandisdoneeitheronce(onSeptember-October)ortwice(inautumnandspring).Themostcommonlyusedherbicideischlorateandstaffworkingonthetrackshouldusespecialandappropriateclothesandundergoyearlymedicalexaminations.Herbicidesmusthavebeentestedandapprovedbytherelevantauthorities.Inurbanareasandwhereprotectionofthewatertableisnecessary,additionalrestrictionsmustbesetbeforedecidingtheuseofherbicides.Theincreasingenvironmentalsensitivityofcitizensexercisespressureonrailwayauthoritiestominimizetheuseofherbicides(asfaraspossibleworkingindaytime,intheabsenceofwindandrain),(187).

Thegrowthofvegetationalongthetrackcanalsobereducedbytheinstallationofanasphaltlayerundertheballastandonthesidepaths.

Inadditiontomechanicalandchemicalmeans,othermethodshavebeenemergedrecently,suchasinfraredorelectromagneticormicrowaveradiation,which,however,arenotyettechnicallyadaptedforrailwaytracks,havealowrateoftreatment,disrupttrainrunningandrequire2÷3treatmentsperyear,(187).

9.16.2.Criteriaanddosageforapplicationofherbicides

Itisnecessarytocontrolvegetationgrowth,especiallyalongthesidesofarailwaytrack,(Fig.9.21).Chemicalcontrolofvegetationgrowthshouldbe

limitedtotheinspectionwalkway(D1),theballastshoulder(C1+C2),theballast(B)andtheinter-trackarea(A).Eachoneoftheabovesectionsmustbetreatedwithdifferenttypesandquantitiesofherbicides.However,theballast(B),thehorizontalsectionoftheballastshoulder(C1)andtheinter-trackarea(A)shouldonlybetreatedwhenabsolutelynecessary,(187).

Fig.9.21.Segmentationoftrackanduseofherbicides,(187)

Herbicidesmustnotbecorrosive,combustible,inflammableorconductingsubstances.Theeffectofherbicidesshouldcorrespondtothetrackclassificationandthedosageshouldbeadaptedtotheexistingvegetation.

Tracksectionswhichareshortlytoberenovatedmustnotbechemicallytreated.Newballastmustnotbetreatedforthefirstfewyears,whenvegetationissparse.Atlevelcrossings,onbridgesandintunnels,asageneralrule,notreatmentshouldbeundertaken.

Environmentalawarenessputssevererestrictionsontheuseofherbicides.Theiruseshouldbelimitedandtheso-calledspreadfactor*mustbegreaterthan150.Theirpersistence(i.e.thetimerequiredfortheherbicidestobetransformed)mustnotexceed9÷12months.Theiracutetoxicity,expressedbymeansoftheLD50index*,mustbegenerallygreaterthan500toavoidoralabsorptionandgreaterthan2,000toavoidskinabsorption,fortheanimalsincontactwiththeherbicides,(187).

Vegetationcontrolalongrailwaylinesshouldnotharmtheenvironment.Thisfactandtheincreasingpressuretocutcostsforvegetationcontrolmotivatedseveralrailwaysandinternationalinstitutions(suchastheUIC)tolaunchresearchprojectsaimingatbalancingenvironmentalprotectionand

vegetationcontrol.

9.17.Earthquakesandthebehavioroftrackandthesubgrade

Manyareasoftheworldsufferfrequentlyfromearthquakes.Itisacrucialproblem,whichhastwoaspects,(179):a)designanddimensioningofstructures(bridges,tunnels,buildings),trackandsubgrade.Structuresmustbestudiedinrelationtothemaximumseismicacceleration(whichcanattainvaluesupto3m/sec2),whichisdecidedineachareaandcountryinrelationtoitsseismicity.Allstructuresmusthavesuchmechanicalstrengths,soastoavoidcollapsingeveninthemostcatastrophicearthquake.Inareaswithveryhighseismicity,themostefficientwayistohavebridgestotallyisolated,whichisachievedthroughdampersbetweenthestructureanditssupports,(Fig.9.22).

b)Protectionoftraintrafficduringanearthquake.Thiscanbeachievedbyinstallingasystemofseismicsensorsalongthetrack,whichareconnectedtoanalarmcenter.Eachsensorcontainsanaccelerometerandisinstalledinamechanicallyprotectedbox.Ifalevelofaccelerationgreaterthan0.65m/sec2isregistered,trafficmustbeimmediatelystopped.Forvaluesofaccelerationbetween0.40m/sec2and0.65m/sec2,areductionofpermittedspeedsissuggested.Analarmorderisgivenifthreeconsecutivesensorshavesentanalarmmessagewithin5seconds.Allsystemsmusthaveahighreliability:afalsealarmisconsideredastolerableonlyoncewithinaspanof30years,(182).

Fig.9.22.Railwayconcretebridgetotallyisolated,inaregionofhighseismicity

*CBR(CaliforniaBearingRatio)istheratioofthevalueofload,inordertoachievesettlementof0.1inch(2.54cm)ofasampleofthematerialunderstudytothevalueofload,whichresultsinthesamesettlementofasimilarsampleofareferencematerial.

*Plasticityindex(PI)isthedifferencebetweenliquidityandplasticitylimits,whereliquiditylimit(LL)isthewatercontentofthesoilatthetransitionbetweenliquidandplasticstateandplasticitylimit(PL)isthewatercontentofthesoilatthetransitionbetweenplasticandsolidstate.

*FormerinitialsoftheFrenchnameoftheResearchDepartment(“OrganismedesRechercesetd’Essais”),actuallynamedERRI(EuropeanRailResearchInstitute),oftheInternationalUnionofRailways(UIC).

1TechnicaldescriptionofthisequipmentcanbefoundinTechnicalSpecificationofUICunderCode722R,(189).

*Spreadfactorisdefinedas:

whereKd:thequantityofactivesubstanceinanherbicidewhichisabsorbedinμgpergofsoilwater,balancedwith1μgofactivesubstancepermlofwater

c:thepercentageoforganiccarboncontentofthesoil*LD50(lethaldosein50%ofcases)indexmeasurestheacutetoxicityofanherbicideandisexpressedinμgofactivesubstanceperkgofbodyweightforresearchcarriedoutinanimalsexposedtotheherbicide.

10TheRail

10.1.Railprofiles

Railssupportandguidethewheelsofthetrainvehicles.Theirprofilehasbeentheobjectofcontinuousimprovementsincetheappearanceofrailways.

Ofthefirstrailprofiles,theonlyonesurvivingtothisdayisthegroovedrail,(Fig.10.1),whichisstillinusealongtrackswheretherailtopandthepavementsurfaceareatthesamelevel.Theseincludetracksintramwaylines,inlevelcrossingsandinportfacilities.

Fig.10.1.Groovedrail

Thedouble-headedorbullheadrail,(Fig.10.2),waswidelyusedinthe19thcentury,withtheexpectationthatwhentheuppersectionwaswornout,therailcouldbereversed;inthiswayitwasexpectedthatthelowerpartcouldbeused.Factsdidnotvindicatethisassumption,however,andthedouble-headedrailwasabandonedinmanycountriesatthebeginningofthe20thcentury,althoughitisstillinuseonsomerailwaysandmetros(e.g.intheUnitedKingdomandelsewhere).

Fig.10.2.Double-headed(orbullheadrail)

Therailprofile,whichfinallyprevailedandiscurrentlywidelyused,istherailwithbase,(Fig.10.3),alsoknownastheflatbottomrail,orVignoles-typerail,namedaftertheAustralianengineerwhodesignedit.Thisrailconsistsofthehead,thewebandthebase(foot),(Fig.10.3).Theprincipalcharacteristicsofitscross-sectionaretheweightwperunitlengthandthemomentofinertiaI.AconstantgoalhasbeentomakeanyincreasesofwcontingentonaproportionallygreaterincreaseofI,toensurethattheI/mratioincreasesfasterthanw.Thishasledtoaconstantincreaseoftheheightoftherail.

Fig.10.3.FlatbottomorVignoles-typerail;U36section(withaweightof50kg/m)

TheflatbottomorVignoles-typerailcross-sectionwasformulatedonthebasisoftheneedtojoinraillengthstogether,whichcanberealizedwithfishplates(seesection10.12).Theextensiveuseofcontinuousweldedrails(seesection10.13),however,islikelytoleadinthefuturetoachangeintherailprofile.

Theincreaseofaxleloadandtrainspeedhasincreasedrailloading.Thecross-sectionsofstandardgaugerailshavebeenstandardizedbytheUIC,withmaintypesUIC50(weight:50.18kg/m),UIC54(weight:54.43kg/m),UIC60(weight:60.34kg/m)andUIC71(weight71.19kg/m).Figure10.5(section10.4),illustratescross-sectionsofrailprofilesUIC50,54,60and71.

ThisoldstandardizationofUIChasbeenmodifiedbytheEuropeanstandardEN13674-1,accordingtowhichrailprofilesareidentifiedbytheirweightpermeteroflengthfollowedbytheletterEandaserialnumber.Forinstance,theUIC50railprofile,accordingtotheEuropeanstandardization,isreferredtoas50E1.

10.2.Manufacturingofrailsteel

Thesteelindustrymanufacturesrailsfollowingeithertheoxygenprocessortheelectricarcfurnacetechnique.Inthepast,Ingotcastinghasbeenalsoused.

Thetechniqueofcontinuouscasting,(Fig.10.4),hasbeenusedforsomeyearsandcanguaranteearailproductionmorehomogeneousthaninthepast,(159).

Manysteelmanufacturershaveequipmentforthecontinuousqualitycontrolofrails,bymeansofFoucaultcurrents,inordertodetectsurfacedefects.

10.3.Mechanicalstrengthandchemicalcompositionofrailsteel

10.3.1.Mechanicalstrength

Theincreaseoftrainspeedandaxleloadnecessitatedtheimprovementofthemechanicalstrengthofsteelusedforrails.Thegreatesttensilestrengthwas50kg/mm2in1882,whiletodayitis70÷120kg/mm2.Alargeincreaseinrailsteelmechanicalstrength,however,maycausebrittlefailureandforthisreasonafurtherincreaseofthetensilestrengthisnotdesirable.

Fig.10.4.Continuouscastingmachineformanufacturingrailsteel

Therailsteelqualitymaybedistinguishedintwocategories:–normalsteelquality,withanultimatetensilestrengthof70÷90kg/mm2,–hardsteelquality,usedmainlyoncurves,levelcrossings,etc.,withanultimatetensilestrengthof90÷120kg/mm2.

10.3.2.Chemicalcomposition

Concerningtheirchemicalcomposition,railspresentagreatvariety,(214):

10.3.2.1.Carbon

Increasedcarboncontentincreaseshardnessandresistancetowearbutattheexpenseofductility.Railsteelscontain0.40÷0.80%ofcarbon.

10.3.2.2.Manganese

Allcommercialsteelscontainasmallquantityofmanganeseatapercentageof0.80÷1.70%.Manganeseinexcessofthisquantityleadstoahigherhardness.Increasingmanganeseandreducingcarboncanresultinanequivalenttensilestrength,butinhigherductility.

10.3.2.3.ChromiumandSilicon

Chromiumincreaseshardnessandwearresistance.Steelscontaining2.0÷2.5%ofchromiumand0.30÷0.80%ofcarbonareveryhardandhaveahighvalueoftensilestrength,ofhardnessandofresistancetowear.Thecontentofchromiuminrailsteeldoesnotexceedusually1%.Siliconreducesresilienceandrailshaveamediansiliconcontentbetween0.05÷1.30%.

10.3.2.4.Chromium-Manganese

Thedeleteriouseffectofincreasedcarbononthefatiguestrengthofsteelcanbemoderatedbyusingmoremanganeseandchromium.

10.3.2.5.Equivalentcarbonpercentage

Therelatedeffectsofcarbon,manganeseandchromiumcanbeconsideredtogethertoproduceanequivalentcarbonpercentage,givenbytheformula

Itisfoundthatanincreaseof0.1%inequivalentcarbonraisestensilestrengthby7kg/mm2,(147).

Asfarastherelatedeffectsofcarbon,manganeseandchromiumonwearresistanceareconcerned,ithasbeenrecordedthatanincreaseof0.1%inequivalentcarbonreducesverticalheadwear(seesection10.10below)by4.5÷7.5%,(214).

10.3.3.Railgrades

10.3.3.1.RailgradesaccordingtoUIC

Thesteelindustryhasavarietyofproductsforrailprofiles,whichareclassifiedeitheraccordingtoUIC(basedontensilestrength)oraccordingtoEuropeanstandardEN13674-1(basedonhardness).

RailgradeUIC700wasusedextensivelyuntiltwodecadesago,andhasaminimumtensilestrengthof68kg/mm2.RailgradeUIC900A(orgradeR260accordingtoEuropeanstandard)hasaminimumtensilestrengthof88kg/mm2

andahardnessof300HB.AvariationofthisisUICgrade900B,withamaximumtensilestrengthof103kg/mm2.ThereisalsorailgradeUIC1100withamaximumtensilestrengthof108kg/mm2andgrades1,200,1,200HH,1,400.Table10.1givesthechemicalcompositionandmechanicalcharacteristicsforthevariousrailgradesaccordingtoUIC.

Table10.1.Chemicalcompositionandmechanicalcharacteristicsforthevariousrail

gradesaccordingtoUIC,(207)

10.3.3.2.RailgradesaccordingtoEuropeanstandard

RailgradesaccordingtotheEuropeanstandardEN13674-1areillustratedinTable10.2,inwhichchemicalcomposition,mechanicalresistancesandhardnessaregiven,(205).

Table10.2.Chemicalcompositionandmechanicalcharacteristicsforthevariousrail

gradesaccordingtotheEuropeanstandardEN13674-1,(205)

10.3.3.3.Choiceofrailgrade

Thechoiceoftheappropriaterailgradeforatrackmusttakeintoaccounttheannualtrafficloadandtheradiusofcurvatureofthetrack.Guidelinesconcerningrailgrades,ofUICandofvariousEuropeanrailways,areillustratedinTable10.3.However,accordingtotheEuropeantechnicalspecificationsforinteroperability,theminimumhardnessofrailshouldbe200HB,(134),(205),(207).

Table10.3.GuidelinesofUICandofvariousEuropeanrailwaysforthechoiceofrailgrade(inrelationtotheradiusofcurvatureR)ofatrackwithamaximumaxleloadof22.5tandanannualtrafficloadofatleast20·106t,(205),(207)

Americanrailwaysusesteelqualitieswithaminimumtensilestrengthof90kg/mm2andahardnessof250HB.

Forrailssupportingheavyaxleloads,itmaybenecessarytouserailgradeswithahighertensilestrength(110÷120kg/mm2)andhardness(340÷380HB),whichareproducedfollowingaprocedurecalledthermichardening,(159).

10.4.Choiceofrailprofile

10.4.1.Standardgaugetracks

Thechoiceofrailprofiledependsmainlyonthetrafficloadaswellasontheexpectedlifetimeoftherail.Forastandardgaugetrack,itiscustomarytouseUIC54railforalowtrafficloadtrackandUIC60railformediumandheavytrafficloadtracks.UIC71profilewasintroducedsomeyearsago,buthasnotbeenusedextensivelyuntiltoday,(Fig.10.5,p.232).

Thechoiceofrailprofileshouldtakeintoaccountthefollowingparameters:speed,axleload,trafficofthetrack,sleeperspacing,lifetimeandeventualreuse.However,railwayauthoritieshaveestablishedpracticalandeasytouseguidelines.Thus,ithasbeencustomaryinEuropeforstandardgaugetrackstouseforlowtraffic(withadailytrafficloadnotexceeding25,000t)arailprofileUIC54.Forheavytrafficloads(>35,000t),arailprofileUIC60issuggested.Fordailytrafficloadsfrom25,000tto35,000t,iftimbersleepersareused,thenarailprofileUIC54issufficient;ifconcretesleepersareused,thenarailprofileUIC60issuggested,(147).

However,accordingtotheEuropeantechnicalspecificationsforinteroperability,railprofileshouldbeofthetype60E2(whichisprofileUIC60slightlymodified),withaweightof60.18kg/m,aminimummomentofinertiaof1,600cm4andaminimumhardnessof200HB,(134).

10.4.2.Metricgaugetracks

Thereisavarietyofrailprofilesformetricgaugetracks,whichhaveaweightrangingfrom30kgtoeven60kgpermeteroflength.ThemostcommonlyusedrailprofileformediumandhightrafficvolumemetricgaugetracksisS49(weighing49.05kg/moflength),(Fig.10.6),whereasformetricgaugetrackswithalowtraffic,railprofileS33(weighing33.47kg/moflength)canbeused.

Thechoiceoftheappropriaterailprofileformetricgaugetracksisdonebytakingintoaccountvaluesofspeedandaxleload.Table10.3aillustratesrecommendationsofUICforsuggestedrailprofilesformetricgaugetracks,(140).

Table10.3a.Choiceofrailprofileformetricgaugetracks,(140)

10.4.3.Broadgaugetracks

Broadgaugetrackssupportgreateraxleloadscomparedtostandardgauge

tracks.Forthisreason,heavierrailsareusedinbroadgaugetracks.Figure10.6illustratesarailprofileextensivelyusedinRussia(withaweightof65kgpermeteroflength).

Fig.10.5.RailprofilesUIC50(50E1*),UIC54(54E1),UIC60(60E1)andUIC71(71E1)forstandardgaugetracks,(206)

Fig.10.6.Railprofilesformetricgaugeandbroadgaugetracks,(206)

10.4.4.Geometricalcharacteristicsofvariousrailprofiles

Table10.4(nextpage)presentsapanoramaofrailprofilesforstandardgaugetracksinusebyvariousrailwayauthoritiesallovertheworld.

10.5.Transportofrails

Thetransportofrailstotheirfinaldestinationshouldbeperformedwhiletakingallmeasurestoreduceverticaldeflections.Figure10.7illustratesforarailof36mlongpointsofsuspensionduringitstransport.

Fig.10.7.Transportofarailof36mlong

10.6.Analysisofstressesintherail

Thetotalstressesdevelopedintherailarethesumof:

stressesatthewheel-railcontact(calledalsoHertzstresses),stressesresultingfromrailbendingontheballast,stressesresultingfrombendingoftherailheadontheweb,stressesresultingfromthermaleffects,plasticstresses,remainingintherailaftertheremovalofexternalloads.Withtheexceptionofthelastcategory,allotherstresseswillbecalculated

withtheassumptionofanelasticbehavior.Asdiscussedinsection8.4.4.2,boththeoryandexperimentsshowthatinmostcasesrailhasanelasticbehavior.

10.6.1.Stressesatwheel-railcontact

Theproblemofstressesdevelopedatthewheel-railcontactwasexaminedbyDangVan,(219),inaccordancewithHertz’sassumptionthatthecontactsurfacebetweentwocurvedelasticbodies(wheel-rail,seeFigure10.8)isellipticalandthestressdistributionalongthecontactsurfaceissemi-elliptical.Measurementshaveshown,however,thatforwheeldiametersattherangebetween60cmand120cm(coveringthemajorityofcases),thefollowingtwo-dimensionalsimplifiedsimulationgivessatisfactoryresults(Eisenmann’stheory).

Fig.10.8.Wheel-railcontact

Table10.4.Geometricalcharacteristicsofvariousprofilesofrail,(206)

Assumingthatallradiiofcurvature(withtheexceptionofthewheelradiusR(inmm))areinfiniteandthatthewheelloadQ(inNt)isuniformlydistributed,

themeanHertzstressσμisgiven,accordingtotheEisenmannanalysis,bytheformula,(222):

SubstitutingtheusualvaluesofE=2.1·106kp/cm2,ν=0.3,b=6mm,thefollowingformulaisderived:

TheEisenmann’ssimplifiedsimulation,givesfortheshearstressthedistributionofFigure10.9withamaximumvalue:

Themaximumshearstressatthewheel-railcontactoccursatadepthof4÷6mmfromtherollingsurface(wheeltread),(222).

Fig.10.9.Shearstressesatthewheel-railcontact

10.6.2.Bendingstressesoftherailontheballast

Therailissimulatedasacontinuousbeamonelasticsupports,(209),(211).Thegeneralequationofmechanics:

givesthefollowinganalyticalformulaforthebendingstressesσb:

Fig.10.10.Simulationofrailforthecalculationofbendingstresses

where:Q :thewheelload,Ir :themomentofinertiaofrailintheverticaldirection,

hr :thedistancebetweenrollingsurfaceandneutralaxisoftherail,

k :thetrackindex(seesection8.2.2)u :displacement,γr :

10.6.3.Bendingstressesoftherailheadontherailweb

Therailheadissimulatedasabeamlyingonanelasticsub-base.Theresultingstressesσharegivenbytheanalyticalformula,(225):

where:hc:thedistancebetweenrollingsurfaceandneutralaxisoftherailhead,Ic:themomentofinertiaoftherailhead,γc:

10.6.4.Stressescausedbytemperaturechanges

Stressescausedbytemperaturechangesaregivenbytheequation:

where:α:therailthermalexpansioncoefficient,Δθ:thetemperaturedifference.

10.6.5.Plasticstresses

Nosatisfactoryelastoplasticanalysiswithspecificnumericalresultsforplasticstresseswithintherailhasbeenconducteduntiltoday.Thisisduetothedifficultyinsimulatinglimitconditionsbetweentherailandthesleeper,(204).

Fig.10.11.Longitudinalplasticstresses attheplaneofsymmentryoftherail

MeasurementshaveyieldedaplasticstressdistributionasillustratedinFigures10.11and10.12.

LaboratorytestsconductedbytheJapaneserailwayson50T-profilerails(weighing53kg/m),havegivenastressdistributionasillustratedinFigure10.13,(224).SimilarresultswereobtainedbytheGermanrailwaysforrailprofileS49(weighing53kg/m),(215).

Fig.10.12.Transverseplasticstresses attheplaneofsymmetryoftherail,(224)

Fig.10.13.Plasticstressesinrailprofile50T(weighing53kg/m),(224)

10.7.Analysisofthemechanicalbehaviorofrailbythefiniteelementandthephotoelasticitymethods

Themechanicalbehaviorofrailmayalsobesimulatedbythefiniteelementmethod,(Fig.10.14),(146),(204).Insuchasimulation,however,itisstillverydifficulttoaccuratelystudythelimitconditionsattherail-sleepercontact.Therefore,itiscustomarytoincludeboththerailandthesleeperinthefiniteelementanalysis.

Unilateralcontactandinequalitymechanicstheories(presentedinsection8.11)canbeimplementedfortheaccuratestudyoftherail-sleepercontact,butrecentresearchdidnotconcludewithspecificnumericalresults,(137),(161).

Finally,inordertoinvestigatestressdistributionintherail,methodsofphotoelasticitymaybealsoused.Figure10.15illustratescurvesofequalshearstressbasedonmethodsofphotoelasticity.

Fig.10.14.Analysisoftherailwiththeuseofthefiniteelementmethod,(146)

Fig.10.15.Analysisofstressesintherailwiththeuseofthephotoelasticitymethod,(147)

10.8.Railfatigue

10.8.1.Fatiguecurveandraillifetimedetermination

Fatiguecanbedefinedasthegradualdecreaseofmechanicalstrengthinamaterialundertheinfluenceofrepeatedloading,aslongasthedevelopedstressexceedsaminimumvalueσo,knownasthefatiguelimit.Forstressesbelowthefatiguelimit(σ<σo),fatiguephenomenadonotoccur.

Fig.10.16.Fatiguecurve

Ifstressesexceedthefatiguelimit(σ>σo),thenthemechanicalstrengthgraduallydecreases,leadingtofailureofthematerialforstressvalueslowerthanvaluescausingfractureduringthefirstloadingcycle.

Theoreticalandexperimentalresearchofthefatiguephenomenonmainlycenterontwotopics:a.Determinationofthefatiguecurve(alsoknownastheWöhlercurve,afterthe

nameoftheGermanengineerwhofirstanalyzedrailfatigue).Thefatiguephenomenonoccursforstressesσ>σο,(Fig.10.16).

b.Forastresshistorywithinthefatiguearea,determinationofthestrengthreservesofthematerial.Letσ1bealoadinghistory,σ1>σο,forwhichthelifetime,attheendofwhichmaterialfailurewilloccur,isN1loadingcycles.Thematerialissubjectedton1loadingcycles,andn1<N1.Letσ2beasecondloadinghistory,σ2>σo,which,intheabsenceoftheσ1loading,wouldhavemadethelifetimeN2loadingcycles.Unknownisthenumbern2ofloadingcycleswhichwillleadtofailureofthematerial.TheanswerisgivenbytheMiner’srulewiththeapproximateformula,(148):

Inthecaseofmoreloadinghistories,theMiner’sruleisgeneralizedasfollows:

Theoriginofthefatiguephenomenoninmetalsinvolvesinternaldiscontinuities,whicharepresentfromthebeginning(phaseofproductionofsteel).Ifthedevelopedstressesaresufficientlysmall,theseinternaldiscontinuitiesdonotpropagateandthusthestateofequilibriumismaintained.However,whenstressesexceedthefatiguelimit,theninternaldiscontinuitiespropagate,expand,mergeandmaycausefractureofthematerialbecauseoffatiguewithoutanyvisiblemacroscopicdeformation.

10.8.2.Railfatiguecriterion

Therailfatiguephenomenonhasbeenextensivelyresearched,bothattheexperimental,(221),andatthetheoreticallevel,(219),soastoinvestigatetheconditionsleadingtothecommencementofinstabilityduetoaninternaldiscontinuity.Onthebasisofthefindingthatinternaldiscontinuitiestendtopropagatetowardsgrainswithcrystallographicplaneslesswellorientedtoresistexternalloads,andtakingintoconsiderationaseriesoflaboratorytestresults,DangVanformulatedacriterion,namedafterhim,accordingtowhichrailfatiguedevelopsintwophases,(219):1.Afirsthardeningphase,duringwhichstressesdevelopundertheinfluenceofcyclicplasticstrainsandtendtoanequilibriumstate.Assumingisotropic

hardeningofsteel,itwasdeducedthatlocalstressesσij(t)arerelatedtomacroscopicstressesΣij(t)(thoseresultingfromthecontinuummechanicstheory)bytheequation:

where:αij:thegrainorientationtensorm:theslidingdirectionn:perpendiculartotheslidingplaneTo:themeanshear,definedforthen-cycleas:

2.Asecondphaseduringwhichthepropagationofinternaldiscontinuitiesstartsingrainsthatarealreadyinaplasticstate,whilesurroundinggrainsareinanelasticstate.Sincethenumberofmoleculesremainsconstant,thecreationofinternalvoidsresultsinanincreaseinvolume,afactjustifyingtheinvestigationoftheroleofthespherical(orhydrostatic)tensor(σκκ/3)*inthestudyoftherailfatiguephenomenon,

where:sij:thedeviatortensor,δij:theKronecker’sdelta(δij=0fori≠jandδij=1fori=j).

MacroscopicstressesΣij(t)resultfromthecontinuummechanicstheory,whileexperimentalfindingsdeterminen,m,andthereforethetensorαij.

Localshearτ(t)ingrainswiththeworstorientationwillbe:

where:T:themacroscopicshearTo:themeanshear

Analysisoftherailfatiguephenomenonhasshownthat,(219):Maximumshearstressdevelops10÷15mmbelowtherollingsurface,(Fig.

10.17).Itshouldbenotedthatthisconclusionhasbeenconfirmedbyaseriesoflaboratorytests,(221),(223).Maximumstressesoccurinplanesinclined30°tothevertical.Anincreaseinwheeldiametercausesanincreaseofinternaldiscontinuities.InternaldiscontinuitiescausingfatigueareproportionaltoaxleloadQraisedtoapowerawithavaluebetween3and4andcloserto4.Thus,railfatigueisarelationtoQa.

Fig.10.17.Shearstresseswithinarail,(221)

Fig.10.18.Characteristicsofaninternaldiscontinuity

10.8.3.Evolutionofaninternaldiscontinuity

Theevolutionofaninternaldiscontinuity,ellipticalinform,withmajoraxis2αc,isafunctionofthestressintensityΔσexertedonthediscontinuityperimeter.ForvaluesΔσ<Δσcrit,discontinuitydimensionsremainunaffectedbyexternalloading.TheregionII,(Fig.10.18),iswherethediscontinuitypresentsalargeincrease,calculatedbytheequation,(210),(220):

wherecandncarecoefficientsresultingfromlaboratorytests.Finiteelementanalysisenablesthecalculationofthenumberofloadingcyclesmakinganinitialdiscontinuityreachaparticularvalueasafunctionofcyclesofwheelload,(215).

AmoreempiricalrelationgivingtheevolutionofaninternaldiscontinuityYo

asafunctionoftrafficloadTofthelinehasbeenderivedfromresearchconductedwithintheORE,(221):

where:Y:valueofthediscontinuityafterpassageoftrafficloadTYo:initialvalueofthediscontinuityT:trafficloadoftheline(inmilliontonsperyear)

Arailrunsaseriousriskoffracturewhentheexpandingandmergingofinternaldiscontinuitiescovermorethan55%ofthesurfaceoftheheadoftherail.

10.9.Raildefects

10.9.1.Definitionofraildefects

Internaldiscontinuitiesofrailwhichmaygiverisetorailfatiguearecalledraildefects.Railalterationsofamechanicalnatureoccurringundertheinfluenceofpassingtrainsarealsoconsidereddefects.Raildefectsshouldbeclearlydistinguishedfromtrackdefects,thelatterbeingdefinedasthedeviationsofactualfromtheoreticalvaluesofthegeometricalcharacteristicsofthetrack.Trackdefectsareexclusivelytheconsequenceoftraintraffic,theyareofamacroscopicandgeometricnatureandusuallytheyarerectifiedbytrackmaintenance,(seesection16.4).Onthecontrary,raildefectsareduetoinitialmanufacturingimperfectionsoftherail,areofamechanicalandmicroscopicnature,andinmostcasesarenon-reversible.

Railsmaybecomedefectiveinthetrackinanyoneofthefollowingways,(218):•Brokenrail:anyrailwhichisseparatedintotwoormorepiecesorarailfromwhichapieceofmetalbecomesdetached,causingagapofmorethan50mminlengthandmorethan10mmindepthintherunningsurface.

•Crackedrail:anyrailwhichshowsanywherealongitsspanandirrespectiveoftheprofilesectioninvolvedoneormoregapsofnosetpattern,apparentornot,theprogressionofwhichcouldleadtobreakageoftherailfairlyrapidly.

•Damagedrail:anyrailwhichisneithercrackednorbroken,butwhichusuallyshowsotherdefectsgenerallyontherailsurface.Raildefectsmaybelocatedatrailends,awayfromrailendsorinwelding

zones.

10.9.2.Codificationofraildefects

Raildefectshavebeenstudied,classifiedandcodifiedbytheInternationalUnionofRailways.Thus,broken,crackedanddamagedrailsaretheobjectofacodethatmaycompriseasmanyasfourdigits,(Table10.5),(208),(218):Thefirstdigitindicates:1.defectsinrailends,2.defectsawayfromrailends,3.defectsresultingfromdamagetotherail,4.weldandresurfacingdefects.Theseconddigitindicates:–theplace,intherailsection,wherethedefectoriginated,–thetypeofweldingwheneverweldorresurfacingdefectsareinvolved.Thethirddigitindicates:–thepatternofthedefectinthecaseofabrokenorcrackedrail,–thenatureofthedefectinthecaseofadamagedrail,–thecauseofthedefectinthecaseofadamagedrail.

Thefourthdigitmakesitpossible,asandwhenrequired,forafurtherclassificationtobemadebytypeofdefect.Theprincipalraildefects,whicharethecauseofthemostseriousrisksof

railfatigueandcanprovokefailure,aredescribedbelow,(218).

Table10.5.CodificationofraildefectsaccordingtotheUIC,(218)

10.9.3.Defectsinrailends

10.9.3.1.Longitudinalverticalcracking(Raildefect,accordingtotheUIC,113,Fig.10.19),causingverticalcracks,whichmayexpandandsplittherailheadintwo.Thisisarailmanufacturedefect.Itisdetectedbyultrasonicequipment,andtheaffectedrailshouldbeimmediatelyreplaced.

Fig.10.19.Longitudinalverticalcracking,(218)

10.9.4.Defectsawayfromrailends

10.9.4.1.Tacheovale(RaildefectUIC211,Fig.10.20).Thiscorrespondstoaninitialinternalovaldiscontinuity,causedbythermaleffectsduringrailmanufacture.Itexpandstoreachtherailsurface.Itthenbecomesvisibleonthewebfaces.Breakageoftherailisimminentatthisstage.Thisdefectmaybetheoriginofveryseriousproblemsandevenreachepidemicproportionsinrailsofthesamemanufacture.Itisdetectedwiththeaidofultrasonicequipment.Mostresearchworkonrailfatiguecentersonthisdefect.

Fig.10.20.Tacheovale(expansionofaninitialinternaldiscontinuity),(218)

10.9.4.2.Horizontalcracking(RaildefectUIC212,Fig.10.21),referringtohorizontalcracksoftherollingsurfaceoftherail.Itoriginatesatthemanufacturingstage(initialinternaldiscontinuities)andmaycauselocaldepressionoftherunningsurface.Itisdetectedeithervisuallyorbyultrasonicequipment.

10.9.4.3.Rolling(running)surfacedisintegration(RaildefectUIC221,Fig.10.22),correspondingtoagradualdisintegrationoftherollingsurfaceoftherail.Surfacedefectsareofmetallurgicaloriginandcanbedetectedduringtrackmaintenanceinspections;affectedrailsarereplacedatscheduledmaintenancesessions.

Fig.10.21.Horizontalcracking,(218)

Fig.10.22.Rollingsurfacedisintegration,(218)

10.9.4.4.Short-pitchcorrugations(RaildefectUIC2201,Fig.10.23).Theircauseistraintrafficandtheyconsistofcorrugationswithawavelengthλ=3÷8cm.Theycanprovokemanyadverseeffects:highfrequencyoscillationofthetrackleadingtohigherrailstresses,concretesleeperfatiguewithcrackingintherailseatarea,looseningoffastenings,acceleratedwearofpadsandclips,prematurefailureofballastandthesubgrade,anincreaseby5÷15dB(A)innoiselevel.Thisdefectisdetectedeithervisuallyorbyappropriaterecordingequipment.Itisrepairedbypassageofspecialequipment,whichgrindsandsmoothstherail.

10.9.4.5.Long-pitchcorrugations(RaildefectUIC2202).Thesehavewavelengthsλ=8÷30cmandoccurmainlyontheinnerrailsofcurveshavingaradiusof600mandsmaller.Thisformofwearismostcommononsuburbanandundergroundrailwayscarryingalargevolumeoftraffic.Detectionandrepairareconductedasinthecaseofshort-pitchcorrugations.

10.9.4.6.Lateralwear(RaildefectUIC2203,Fig.10.24).Thisaffectsouterrailsincurvesandresultsfromrollingstockstresses.Ittakesasinusoidalformwithaminimumvalueattherightanglewiththefishplatedjoints.Lateralwearbecomesdangerousbeyondacertainpoint,asitaffectsthetrackgauge.Thevariousrailwayauthoritiesspecifythepermissiblevalueoflateralwearoftherailhead,(seesection10.10).

10.9.4.7.Shellingoftherunningsurface(RaildefectUIC2221).Irregulardeformationoftherunningsurfaceisobservedpriortotheformationofshells,severalmillimetersdeepinthemetal.Thecross-sectionoftheseshellsisextremelyvariable.Shellingisnotanisolateddefect.Italwaysoccursoverawidearea.Detectionisdoneeithervisuallyorbyultrasonictesting.

Fig.10.23.Short-pitchcorrugations

Fig.10.24.Lateralwear,(218)

10.9.4.8.Gauge-cornershelling(RaildefectUIC2222,Fig.10.25).Therailsfirstshowlongdarkspotsrandomlyspacedoutoverthegaugecorneroftherailhead.Thesespotsareearlysignsofmetaldisintegrationwhich,afteraperiodofevolution,arecharacterizedbytheformationoflipsonthesideface,ofcracks

andlastlyofshellinginthegaugecorner,whichcansometimesbequiteextensive.Thisformofshellingusuallyoccursalongtheouterrailsincurveslubricatedtoavoidlateralwear.Itcanbedetectedbyvisualinspection.

Fig.10.25.Gauge-cornershelling,(218)

10.9.5.Defectscausedbyraildamage

10.9.5.1.Bruising(RaildefectUIC301,Fig.10.26).Thisdefectisduetotrafficloadandmaybetheresultofvariouscauses:derailments,draggingparts,damagedtires,handlingoperation,arcing,ortheimproperuseoftools.Crackedandbrokenrailsmustbereplacedattheearliestopportunity.

10.9.5.2.Faultymachining(RaildefectUIC302,Fig.10.27).Thisisduetotrafficloadandmayhaveasoriginthefollowing:improperin-trackdrillingoffootorwebofrail,faultycutting,etc.Itisinspectedvisuallyandmayleadtocrackingandbreakageoftherail,whichshouldbereplacedsoonaftertheproblemhasoccurred.

Fig.10.26.Bruising,(218)

Fig.10.27.Faultymachining,(218)

10.9.6.Weldingandresurfacingdefects

10.9.6.1.Electricflash-buttwelding(transverseandhorizontalcrackingdefects).Defectscomingfromelectricflash-buttweldingmaybeeithertransversecrackingofprofile(defectUIC411)orhorizontalcrackingofweb(defectUIC412).Transversecrackingmayleadeithertoaninternaldefectofthehead(Fig.10.28)ortoadefectlocatedinthefootoftherail(Fig.10.29).Horizontalcrackingdevelopsinacurvedshapeintheweb.Bothtransverseandhorizontalcrackingareinspectedvisually(withaconfirmationbyultrasonicexamination)andmayleadtheaffectedrailtocompletebreakage.Fishplatingshouldbeurgentlycarriedoutanddefectiverailshouldbereplacedwithanewone.

Fig.10.28.Transversecrackingofrailheadduetoaweldingdefect,(218)

Fig.10.29.Transversecrackingofrailfootduetoaweldingdefect,(218)

10.9.6.2.Thermitwelding(transverseandhorizontalcracking)andelectricarcwelding(transverseandhorizontal)defects.Defectsduetothermitwelding(transversecracking(defectUIC421)andhorizontalcrackingofweb(defectUIC422))aresimilar,bothinbehaviorandintreatment,todefectsoccurringinthecaseofelectricflash-buttwelding.Defectsduetoelectricarcwelding(transversecracking(defectUIC431)andhorizontalcrackingofrailweb(defectUIC432))arealsosimilartootherweldingdefects.

10.10.Permissiblerailwear

10.10.1.Verticalwear

Themaximumpermissibleverticalwearoftherailisafunctionofthemaximumtrainspeedandoftrafficload.Tables10.5and10.6giveformedium-speedtracksthemaximumpermissiblewearvaluesoftherailheadaccordingtoBritishandGermanregulations,(214).

Itshouldbenotedthatrailwearcausedbylocomotivewheelsisabout6timesgreaterthanthatcausedbythewheelsofhauledrollingstock.

Table10.5.Maximumpermissibleverticalwearofrail(159mmhigh)accordingto

Britishregulations,(214)

Table10.6.Maximumpermissibleverticalwearofrail(154mmhigh)accordingto

Germanregulations,(214)

10.10.2.Lateralwear

ThemaximumpermissiblelateralwearaccordingtoBritishregulationsisdefinedinrelationtoareferencepointlocated3mmabovethelowestpointoftherailheadandata26°angletotherailaxis(Fig.10.30).

Germanregulationsmeasurewearat45°totherailaxisonalinethroughthecenteroftherailshoulderofthefullcross-section,(Fig.10.31).OnmaintracksandforUIC60railprofiles,lateralwearshouldnotexceed16÷18mm.Thesumoftheverticalandthelateralwearoftherailhead,however,shouldnotexceed25mm,(214).

Fig.10.30.Maximumpermissiblelateralwearofrail,accordingtoBritishregulations

Fig.10.31.Maximumpermissiblelateralwearofrail,accordingtoGermanregulations

10.11.Optimumlifetimeofrail

Determiningtheoptimumlifetimeofarailisnotapurelytechnicalproblem,butshouldtakeintoaccounteconomicaspects.Beyondtheserviceperiodoftherail,thetotalcostincreasessharply,(Fig.10.32).Itisthereforeadvisabletoreplace

therailbeforealltechnicalstrengthmarginsareexhausted.OptimallifetimeofrailisdeterminedbypointK(seeFigure10.32),correspondingtoaminimumoftotalcost,(202),(216).However,arailremovedfromaprincipallinecanbeusedforacertainperiodonsecondarylines.

ForaUIC60railprofile,theGermanrailwaysassumealifetimeofaround40yearsforprincipallinesandaround80÷100yearsforsecondarylines,(142).

Fig.10.32.Calculationoftheoptimumlifetimeofrail

Frenchrailwaysachieveanaveragelifetimeof50÷60yearsandtheBritishrailwaysaround45years.Onceagain,thebestoftheserviceablerailrecoverediscropped,weldedandre-usedforlowercategorylines(seealsoTable5.4).

Fig.10.33.Fishplatesjoiningrails

10.12.Fishplates

Untilabout50yearsago,trackswerelaidinallrailnetworks(andarestilllaidinsomeofthem)byleavinggapsbetweenconsecutiverails,andthenjoiningtherailswithfishplates(Fig.10.33).Thebasicpurposeofthegapswastoabsorblengthvariationsduetotemperaturevariations.

Thefishplatetechniquewasdetrimentaltorailtransportationinseveralways:itsignificantlyreducedpassengercomfort,itcausedconsiderablewheelandrailfatigueandwear,itgreatlyincreasedmaintenanceexpenses,ontheonehandduetothenecessaryinspectionstoensureproperconditionofallfishplatesparts,andontheotherbecauseoftheheightirregularitiesarisinginthefishplateregion.

Instandardgaugetracks,fishplatesareusuallyinstalledevery36or54m,afterpriorweldingoftherailsof18mingroupsoftwoorthree.Acharacteristicoffishplate-joinedrailsistheircapabilityforcontraction-expansion,depending

ontemperaturefluctuations.Everyrailprofilehasacorrespondingfishplatetype,aswellasaparticularformofbolt.

10.13.Thecontinuousweldedrail

10.13.1.Thecontinuousweldingtechnique

Fromthetimewhenrailwayswerefirstintroduced,effortsweremadetoincreasethelengthofrails,theultimategoalbeingacontinuoustrack.Thecontinuousweldedrail(cwr)istheresultofweldingtogetherdiscretepiecesofrailasobtainedfromthemanufacturerinvariouslengths,commonly18m,24m,30mor36mforstandardgaugetracks.Theusualmaximumlengthfortheproductionofrailsisnowadays36m(UnitedKingdom,France,Italy,etc.),butmayattaingreatervaluesinsomecountries(60minGermany,upto108minAustriaandevenupto120melsewhereetc.),(159).Incontrasttofishplate-joinedrails,cwrarecharacterizedbyarailregionwherenotemperature-inducedlengthchangeoccurs.Continuousweldingdoesawaywithfishplates,withalltheobviousbeneficiaryconsequencesthisentails.

Althoughitisatechnicallysimpleconcept,continuousweldingtookalongtimetobeadoptedinrailwaytechnology.Thisdelaywasduetothefollowingreasons,(141),(212):Aspreviouslymentioned,acharacteristicofthecontinuousweldedrailistheabsenceoflengthvariation.Thisisaresultofthefrictionforcesbetweensleeperandballastaswellasbetweenrailandsleeper.Theseforces,however,cannotbeensuredunlesstherail-sleeperconnectionisstable.Thishasbeenenabledoverthelast50yearsbyelasticfastenings(seesection11.9.2.2).Thefatiguebehaviorofwelds,whichundergorepeatedstressesbythepassageoftrains,wasnotadequatelyknown.Researchonweldshasshedlightonthisaspectandtherearenoreservationsconcerningthismatter.Finally,theriskofbucklingwasalsoconsidered,duetothegreatlengthofthecwr.Researchonthemechanicalresistanceoftheballast,whichopposesbuckling,combinedwithatrackweightincrease,hasaddressedtheprobleminasatisfactorymanner.

Inthecaseoftramwaylines,whicharefullyrestrainedbybeingembeddedintheroad,theproblemoflongitudinalforcesdoesnotoccurandlongerrailscouldbeimplemented.

10.13.2.Mechanicalbehaviorofcontinuousweldedrail

10.13.2.1.Assumptions

Inrecentyears,thedevelopmentofnon-linearconstitutivelawsandnumericalmodels,aswellastheknowledgeoffatiguemechanismshavecontributedtoamoreaccurateanalysisofthemechanicalbehaviorofthecwr,attheprice,however,ofcomplexandtimeconsumingcalculations,(203).Forthisreason,railwaysstilluseasimplifiedanalysis,whichgivesasatisfactoryqualitativerepresentationofphenomena,inadditiontorenderingsafety-orientedresults.

10.13.2.2.Simplifiedmechanicalanalysisofcontinuousweldedrail

Itisassumedthatthebehaviorofallmaterialsiselasticandthatballastresistanceisuniformandconstant.ThecontinuousweldedrailissimulatedbyabarofalengthLandacross-sectionalareaS,(Fig.10.34).UndertheinfluenceofatemperaturevariationΔθ,thelengthchangeofthebarwillbe:

Fig.10.34.Simplifiedsimulationofthecontinuousweldedrail

whereαisthethermalexpansioncoefficientofsteel.

Theballastresiststhechangeoflength(resultingfromtemperaturevariations)byaforceF.ThelengthchangeduetoFwillbe:

Totalstressandstrainwillresultfromthesuperpositionoftheeffectsofthetwoforces(ofoppositedirection)previouslymentionedandtherefore:

WearelookingforavalueofFsuchthatthechangeinlength willbezero.Fromequation(10.19)itfollowsthat:

arelationshowingthatforceFisindependentofraillengthbutproportionaltothecross-sectionalarea,thereforedependingontherailprofile.

Fromtheaforementionedequationitcanbecalculatedthataforceof1.85tonsperdegreecentigradeisgeneratedinthecaseofUIC60profileandof1.60tonsforUIC54profile.

10.13.2.3.Distributionofforcesalongacontinuousweldedrail

Forcesgeneratedalongacwrbytemperaturevariationsaretransmittedthroughthefasteningsandsleeperstotheballast.Letrdenotetheballastresistancewithvaluesrangingfrom0.5to1.0tonpermeteroftrack.Thisresistanceisobviouslyzeroattheendofthecwrand,cumulativelyincreasingoveralengthℓA,(Fig.10.35),itgeneratesaforceequaltoF.Therefore,accordingtoequation(10.20)itwillbe:

Fig.10.35.Diagramofforcesdevelopedwithincwr(O=cwrleftend;O’=cwrrightend)

Equation(10.21)gives:

ThelengthℓAcorrespondstowhatisoftenreferredtoastheexpansionzone.Beyondthislength,theforceFduetotheballastresistancecompletelybalancesouttheforcedevelopedbytemperaturevariationsalongthecwr.Therefore,beyondthelengthℓA,nolengthchangetakesplace.

Consideringanaveragevaluer=0.75t/mfortheballastresistanceandthecaseofUIC60rail(S=76.87cm2),wewillhaveforΔθ=35°C:

whicheveninextremecasescannotexceedalimitvalueintheorderof150m.

Sincethelengthofthecwrcannotbesmallerthan2·ℓA(becauseifitwere,nopointofthecwrwouldremainimmobileduringtemperaturevariations),itfollowsfromtheforegoingthattheminimumlengthofacwris2·150m=300m.

10.13.2.4.Lengthchangesintheexpansionzone

ThecwrundergoesachangeinlengthduetotemperaturevariationsonlyintheexpansionzoneℓA,beyondwhicheverycwrpointremainsimmobile.ThedisplacementofthepointO,(seeFig10.35),causedbythesuperpositionofstraingeneratedbytemperaturevariationandballastresistance,iscalculatedasfollows:i.DuetoatemperaturevariationΔθ,alengthchange willoccur:

ii.Duetoballastresistance,thevalueofwhichiszeroatpointOandr·AatpointA,alengthchange willoccur.Assumingalineardistribution,therewillbearesultantforceequaltor·ℓA/2,producingadisplacement

iii.Combiningequations(10.24)and(10.25),weobtain:

wherek=(α2·E·S)/(2·r)isconstantforaspecificqualityofballast.

10.13.2.5.Railwelding

Railweldingisgenerallyachievedbyflash-buttorelectricarcwelding,usuallyindepots,andfollowedbyinsituweldingintotrackusingoneofthethermitweldingprocesses.

10.13.2.5.1.Flash-buttwelding

Theflash-buttweldingprocessisamethodofjoiningmetalsinwhichtheheat

generated,necessarytoforgethejoint,iscreatedbytheresistanceoftherailsbeingweldedtothepassageofanelectriccurrent.Unlikethethermitweldingprocess,noadditionalchemicalsormetalsarerequiredtomaketheweld.Inflash-buttweldingtheparentmetalisconsumedduringtheweldingcycle,thuscreatingthenecessaryheatalongtherailendsinordertoaccomplishthemergingactionandconsolidatethejoint.Atotallengthofapproximately25÷35mm,dependingupontherailsection,isconsumedperweld.

Flash-buttweldingcanbecarriedoutat:•fixedsitedepots,•mobiledepots,•intrack.

10.13.2.5.2.Thermitwelding

Thethermitweldingprocessisbasedonthereductionofheavymetalsfromtheiroxideswiththeaidofaluminium.Thisreactionisstronglyexothermic,sinceaverylargequantityofheatisgenerated,andisbroughtaboutbythestrongaffinitywhichaluminiumexhibitstowardsoxygen.

ManyEuropeanrailwaysusetheGermanthermitprocesscalledSKV,aweldingprocesswithshortpreheating,(142).

Ineveryweldingprocedure,theappropriatecontrolofweldsiscriticalforthelongevityofthecwr,(203).

10.13.2.5.3.Electricarcwelding

Electricarcwelding(withtheuseofelectrodes)isusedonlywhenthermitweldingisnotpossible.

10.13.2.6.Distressingofacontinuousweldedrail

Itisdesirablethatcwrweldingandlayingbecarriedoutatatemperaturerangingbetweentheupperandlowerextremes,soastominimizecwrstresses.

Regardlessofthecwrlayingtemperature,however,thereductionofstressesprovokedbytemperaturevariationsissought.Thisisachievedbydistressingthecwrandcreatingfreeexpansion(orcontraction)conditions.Distressingisdoneafteranelapseoftimefromthecwrlaying,dependinguponthetrafficloadnecessarytostabilizethetrack.Thisloadisusually100,000tonsinthecaseoftimbersleepersand20,000tonsforconcretesleepers.

Distressingshouldbedonegraduallyalong800÷1,000mandexceptionallyon1,200mtracklengths.Thefollowingprocedurecanbeimplemented,(212):i.Ifthecwrislongerthan1,200m,distressingisdoneinsections.Therailsare

cutattheendofeachsectionandtheendsaredivertedtoenablefreerailchangeoflength.

ii.Fasteningsareloosened.iii.Railsareplacedonrollers(ofadiameterof20mm(ϕ20),every10÷20

sleepers),soastoreducefrictionasmuchaspossible.iv.Furtherreductionoffrictionisachievedbylateralblowsalongtherailby

woodenorplasticsledgehammers.v.Ifatthetimeofdistressing,railtemperatureislessthanthemeantemperature

ofthearea,therailisheated(bypropaneheaters)toreachtheoptimummeantemperature,inordertominimizestressesatextremetemperatures.Obviously,iftherailtemperatureexceedsthemeantemperature,noadditionalheatingisrequired.

vi.Therollersareremovedandthefasteningsaretightened.vii.Distressingshouldtakeplaceonbothrails.Oneachtracksection,distressing

worksshouldbeperformedduringtraffic-freeintervals.

10.13.3.Expansiondevices

Thelengthchangeattheendofacwrwascalculatedinsection10.13.2.4.Inordertoensurethatthislengthchangewillnotbeaccompaniedbyexcessivestressesatcertainsensitivepartsalongthetrack(e.g.theendsofsteelbridges,stationentrances-exits,etc.),expansiondevicesareinstalledatthesepoints.

Figure10.36illustratesthedetailsofanexpansiondeviceforUIC54rail.Thereisagreatvarietyofsuchexpansiondevicetypesamongtherailwaynetworks.

Expansiondevicesshouldnotbeusedinthefollowingcases:•ontransitioncurvesbetweenstraightandcurvedtrack,•oncurveswithsmallradiusofcurvature(lessthan800m),•onlargebridgeswithoutballast:–ifthebridgeismorethan30mlong,expansiondevicesarerequiredateachend–ifthebridgeislessthan30mlong,cwrmaybelaidwithnoexpansiondevices.

Fig.10.36.ExpansiondeviceforUIC54rail(alldimensionsinmm)

10.13.4.Advantagesofthecontinuousweldedrail

Althoughthecostofinstallingcwrishigherthanthatoffishplatedtrack,anadequatereturnofcapitalfortheinitialinvestmentisprovidedbythereducedmaintenancecostofthetrack,improvedtrackstability,higherrunningspeeds,lowerpowerconsumption,andimprovedpassengercomfort.Inparticular:cwrofferamuchhighercomfortlevel,evolutionoftrackdefectsismuchslowerwithcwr,fatigueofthevariouscomponentsofthetrackissmaller,stressesdevelopedinwheelsandintherollingstockaregenerallymuchlower.

*EquivalentsymboltoUIC50,accordingtotheEuropeanstandardization.*Itisworthrememberingthatarepeatingsubscriptmeansthesumatallpossiblevaluesofthesubscript(Einstein’snotation):

11Sleepers–Fastenings

11.1.Thevarioustypesofsleepersandtheirfunctions

Sleepers(whicharecalledtiesinNorthAmericaandelsewhere)arethetrackcomponentspositionedbetweentherailsandtheballast.Therailsofthefirstrailwaylinesweremountedonblocksplaceddirectlyontheground.Theneedforbetterloaddistributionledtotheadditionofsleepersandballast.

Sleepersmustensurethefollowingfunctions:•appropriatetransferanddistributionofloadsfromtherailstotheballast,•constantrailspacing,asspecifiedbythetrackgauge,•mountingoftherailsonthesleepersataninclinationfrom1/20to1/40,•adequatemechanicalstrengthbothintheverticalandinthehorizontaldirection.

Alongelectrifiedlines,sleepersshouldmoreoverensure(eitherbythem-selvesorwithaddedaccessories)theelectricalinsulationofeachrailfromtheother.

Thefirstmaterialusedforsleeperswaswood.Itsscarcityandsensitivityledtotheintroductionofsteelsleepersaround1880,whichwerewidelyusedforalongtime.Since1950,advancesinconcretetechnologyhaveledtotheuseofconcretesleepers,whichcanbe:–twin-blockreinforced-concretesleepers,–monoblockprestressed-concretesleepers.

Sleeperspresentlyinstalledalongnewtracksoroverhauledoldonesaremostlymadeofconcrete.However,timbersleepersarealsousedinseveralinstances.Theuseofsteelsleepersisdiminishingandconcreteortimbersleepersusuallyreplacethemattrackrenewals.

Thechoiceofthemostappropriatetypeofsleepershouldbemadeforeachtrackbyafeasibilityanalysis,whichincludesanevaluationandassessmentofthefollowingeconomicandtechnicalfactors:

11.2.Steelsleepers

11.2.1.Formandproperties

Thesteelsleeperisanindustrialproductofsimpleconstruction.Itconsistsofaprofileintheformof∩.Itsendsareforgedtoprovideanchoringintheballast,soastoensuretransversetrackstability(Fig.11.1).

Fig.11.1.Steelsleeper

Therailismountedontothesteelsleeperbyrailspikesfixedbyrailspikeboltsinholesdrilledontothesleepertop.Elasticfasteningsmayalsobeused.

11.2.2.Dimensions,weightandchemicalcomposition

Steelsleepersaremadefromlowcarbonsteelofanultimatetensilestrengthof

40÷60kg/mm2.Generally,sophisticatedsteelshavenotbeenused,andthereforetheyieldstrengthisnear50%oftheultimatestrength.Thechemicalcompositionofsteelsleepersis,accordingtoBritishspecifications:0.15%÷0.19%C,0.55%÷0.75%Mn,0.20%÷0.30%Si,0÷0.035%S,0÷0.035P,(238).

Thefiniteelementmethodandcomputersoftwarehavehelpedinrecentyearstooptimizethecross-sectionofsteelsleeperandincreaseitsmomentofinertia.Figure11.2illustratesthegeometricalcharacteristicsofasteelsleeper(usedintracksforlowspeeds,V<120km/h),weighing70÷80kg.Intheareaoftherailjoints,whereagreatersteelresistanceisneeded,atwin-typesteelsleepercanbeused,weighing130÷140kg.

Fig.11.2.Geometricalcharacteristicsofasteelsleeper

11.2.3.Advantagesanddisadvantages

Steelsleepersareeasilymanufactured,installed,andmaintained.Theykeepthetrackgaugeadequatelyconstantforalongtime.Theirlifetimeisrelativelylong(usually50years)andafterreplacementtheyhavestillacertainvalueasscrapiron.

However,steelsleepershavemanydisadvantages.Theyhavealowtransverseresistance(seesection13.5),afactprohibitingincreasedspeedsontrackswithsteelsleepers.Theirformmakeslongitudinalandtransversetrackpositioningdifficult.Steelsleepersarenoisy,theyrequirespecialinsulatingdevicesforsignaling,andtheirmaintenanceisdifficult.Furthermore,steelsleepersaresensitivetochemicalattacksandparticularlyvulnerableinlines

closetoindustrialandcoastalareas.Alltheabovedisadvantageshaveledtotheeconomicdevaluationandtothegradualwithdrawalofsteelsleepers,particularlyinEurope.

11.2.4.Lifetime

Steelsleeperlifetimerangesfrom30to60yearswithameanvalueof50years,(238).

11.3.Timbersleepers

11.3.1.Form,propertiesandtimbertypes

Engineershavetraditionallytriedtomaketheutmostuseofanyrawmaterialsneartheworkinprogress.Theobviouschoiceforsleeperswastimberandforover100yearstimberwas(withsteel)theprincipalrailsupportusedthroughouttheworld.

Timbersleepersdistributeloadsbetterthanothersleepertypes.Theyareaccordinglyrecommendedfortrackslaidonfairorpoorqualitysubgrade,whereconcretesleeperswouldrequireacomparativelygreaterthicknessfortheballastlayer(seesection12.5.1).Becauseoftheirhighercostandshorterlifetime,theiruseinEuropeispresentlylimitedtoinstanceswhereconcretesleepersarenotused.However,theyarestillextensivelyusedinNorthAmericaandelsewhere.

ThekindsofwoodpresentlyusedfortimbersleepersincludebeechandoakfromEuropeantrees,andazobéfromtropicalones.Pinetreetimberhasalsobeenusedinthepast.Timbersleepersinusebythevariousrailwaystodayaremostlyofazobétropicaltimber,whichisstrongerandmoredurable.Inundergroundtunnels,Australianjarrahhardwoodsleepershavebeenusedextensively.

Timbersleeperssufferfromtheeffectsofthefollowing:–chemicalandphysicaldisintegrationofwoodthroughexposuretoalternatewetanddryconditions,heatanddust,

–attacksbyfungiandinsects.

Thereareseveralmethodsforthetreatmentoftimbersleepers,themostcommonofwhichinvolvesimpregnationunderpressure.Thesubstancesmainlyusedare:–100%creosote,

–creosote/furnaceoil,mixedinvariousproportions,–anumberofotherchemicals,aloneorincombination.

Inordertopreventthetimbersleeperfromsplinteringorslippingontheballast,itisnecessarytocontainthewoodfiberswithintheballast.Thisisachievedbysuitableconfigurationofthesleeperends,whichareeitherbracedwithasteelstrapsurroundingthesleeperendorhavespecialmetalplatesdrivenintotheverticalsectionofthesleeperends.

Timbersleepersareparticularlysensitiveandtheirstrengthdecreaseswithtimeasaresultof:•deteriorationoftheirmechanicalcharacteristics,•influencesofachemicalnature,•influencesofabiologicalnature.

11.3.2.Geometricalcharacteristics

ThegeometricalcharacteristicsoftimbersleepersarespecifiedbyUIC,(239).TimbersleepersinstandardgaugetrackshavetypicaldimensionsasshowninFigure11.3,(239).ThefollowingtolerancesareallowedtothedimensionsillustratedinFigure11.3:

Fig.11.3.Geometricalcharacteristics(dimensionsinmm)oftimbersleepersforstandardgaugetracks,(239)

Length:+40mm,-30mm,Width:-10mm,Height:-5mmInmetricgaugetracks,timbersleepershavethedimensionsillustratedin

Figure11.4,(239).Theallowedtolerancesareproportionatetothoseforstandardgaugetracks.

Fig.11.4.Geometricalcharacteristics(dimensionsinmm)oftimbersleepersformetricgaugetracks,(239)

11.3.3.Advantagesanddisadvantages

Theprincipaladvantageoftimbersleepersisflexibilityandtheresultingbetterloaddistribution.Timbersleepersareaccordinglyrecommendedinthecaseofpoorqualitysubgrades(classifiedasS1).Timbersleepersmoreoverprovidegoodinsulationanddoawaywiththeneedforspecialdevicesforsignalingandelectrictraction.Finally,comparedtoconcretesleepers,timbersleepersareshorterinheight.

Thedisadvantagesoftimbersleepersincludetheirrelativelyshortlifetime,theircomparativelyhighercostinEurope,(thoughthesituationisinverseinotherpartsoftheworld),andtheirlowtransverseresistance(aresultoftheirlowweight),thusprecludinghighspeedsontheirtracks.

11.3.4.Lifetime

Thelifetimeoftimbersleepersdependsonthetimbertypeusedandis:–25yearsforoaktimber(impregnated),–30yearsforbeechtimber(impregnated),–40yearsforazobétropicaltimber(non-impregnated),–45yearsforazobétropicaltimber(impregnated),–50yearsforjarrahorsimilarhardwoodusedintunnels.

11.3.5.Deformabilityoftimbersleepers

Finiteelementanalysisprovidesanaccurateanddetailedcalculationofdeformabilityoftimbersleeperforvarioussubgradequalitiesandhasalreadybeenpresentedinsection8.4.9,Figure8.12.Itcanbeobservedthatthepoorerthesubgradesoilquality,themoreuniformthetimbersleepersettlement,(228).

11.4.Concretesleepers

11.4.1.Inherentweaknessesofconcretesleepers

Monoblockreinforced-concretesleepers,whenfirstintroduced,presentedthefollowingseriousintrinsicweaknesses:apropensityforbrittlefractureundertheinfluenceofdynamictrainloadsandforextensivecracking,leadingtofailure,verylittleresistancetofatigueresultinginhightensilestressesinthecentralpartofthesleeper,which,ifexceedingthetensilestrength,ledtoslippageofthereinforcingbars.

Overcomingthesetwoweaknessesrequired:•layingtherailssothattheydonothavedirectcontactwiththesleepers,byinterposinganabsorbingmaterialtobluntloadimpact.Suchmaterialincludesrubberpads,whichinturnnecessitatetheuseofelasticfastenings,

•usingreinforcingbarswiththesamelifetimeasconcrete.

11.4.2.Thetwotypesofconcretesleepers

Intandemwiththereinforced-concreteandtheprestressed-concretetechnologies,twoconcretesleepertypesweredeveloped:–thetwin-blockreinforced-concretesleeper,consistingoftwotrapezoidalreinforced-concretesectionsjoinedbyaconnectingbar(Fig.11.5),

–themonoblockprestressed-concretesleeper,whichcanbepre-tensionedorpost-tensioned(Figs11.7and11.8).

Stressdistributionunderthesleeper(seesection11.8)hasshownthatinthecentralsectionthedevelopingstressesareverysmall,thereforelessmaterialcanbesafelyusedinthispartofthesleeper.Asaresult,inthecentralpartofthetwin-blocksleeper,theconcretewasreplacedbyaconnectingbar(whichprincipallyservestomaintainthetrackgauge),whileinthemonoblocksleeper(wheretheabovesolutioncannotbeapplied)thecross-sectionatthecentralpartofthesleeperwasreduced.

Thetwin-blocksleeperwasdevelopedinFranceandtheprincipalusersare:Algeria,Belgium,Brazil,Denmark,Greece,Mexico,Netherlands,Portugal,Spain,andTunisia.

Themonoblockpre-tensionedsleeperwasdevelopedintheUnitedKingdomandtheprincipalusersare:Australia,Canada,Hungary,Iraq,Japan,Norway,Poland,SouthAfrica,Sweden,USA,andRussia.

Themonoblockpost-tensionedsleeperwasdevelopedinGermanyandtheprincipalusersare:Austria,Finland,India,Italy,Greece,Mexico,andTurkey.

Ofallnewconcretesleepers,twin-blockaccountforlittlelessthan20%andmonoblockforlittlemorethan80%,(233).

Theuseofconcretesleepersoncurvedtracksisacontroversialissue.Intheirmetricgaugetracks,SouthAfricanrailwaysdonotuseconcretesleepersincurvesofradiuslessthan300m.Ontheotherhand,Canadianrailways,whichexperienceveryextremetemperatures(-40°Cto+30°C),installconcretesleepersinallcurvesofradiuslessthan870m,includingmanycurvesofradiuslessthan200m,withcontinuousweldedrailsandnogaugeextension.Tosomeextentthedifferentapproachesmayarisefromshortcomingsincertainfastenings,(233).

11.5.Thetwin-blockreinforced-concretesleeper

11.5.1.Geometricalcharacteristicsandmechanicalstrength

Figure11.5illustratesthegeometricalcharacteristicsofthetwin-blockreinforced-concretesleeperU41oftheFrenchrailways,whichweighs260kgandhasbeenusedforthreedecadesattheTGVtracks,whicharerunataspeedof300km/h,(232).TheU41sleeperisslightlymodifiedandisusedtodayunderthenameB450,(232).SleepertypeU41issuitablefortrackswithahightraffic

load(UIC1,2groups)andhighspeeds.TheconnectingbarhasaYorLshapedcross-section.Formediumloadtracks(UIC3,4groups)andspeedslowerthan200km/h,ashortertypeofsleeper(namedformerlyU31andtodayB440)withalengthof2.245mandaweightof180kgcanbeused,(Fig.11.6.a).

Fig.11.5.Twin-blockreinforced-concretesleeperU41oftheFrenchrailways(forgroupsUIC1and2andspeedsupto300÷350km/h),(232)

Twin-blocksleepersrequireballastthicknessandstrengthgreaterthanthatrequiredbytimbersleepers.Wheneverthisrequirementismet,thetracklaidontwin-blocksleepershasasatisfactorybehavior.

Particularcareshouldbetakenwhenthesubgradeisofpoorquality.Inthiscasetheballastthicknessshouldbefurtherincreased.

Becauseoftheflexibleconnectingbar,twin-blocksleepersrequireextramaintenance,soastoensurethatthetwoblocksdonottiltdifferentiallyanddonotloosen.

AccordingtotheEuropeanstandardfortwin-blockreinforced-concretesleepers,thesteelconnectingbarmustfulfillthefollowingrequirements,(229):–chemicalcomposition:0.28%<C<0.80%,0.45%<Mn<1.40%,P<0.08%,S<0.08%,Si<0.50%,–mechanicalcharacteristics:Tensilestrengthmustrangebetween550÷1,030MPa.Forsteelyieldstrength≥400MPa,minimumelongationcanbe≥8%,whereasforyieldstrengthbetween350÷400MPa,minimumelongationcan

be≥14%,–Brinellhardnessmustbe160÷300.

11.5.2.Advantagesanddisadvantages

Duetoitsgreatweight,thetwin-blocksleeperprovidesverysatisfactorytransversetrackresistanceandallowsforhighspeeds.Itkeepstrackgaugewithinsatisfactorytolerancesandhasalonglifetime.Itcanbemanufacturedinanycountryandinmanycountriesislessexpensivethanthetimbersleeper.

Themechanicalbehavioroftwin-blocksleeperislesssatisfactorywhentheballastdoesnothavethesuitablethicknessandmechanicalcharacteristics.Loaddistributionandflexibilityarelesssatisfactorywithtwin-blockthanwithtimberormonoblocksleepers.Inaddition,twin-blocksleepersrequireelasticfasteningsand,duetotheirgreatweight,handlingisdifficult.Thetwin-blocksleeper(incontrasttothetimbersleeper)requiresspecialaccessories,soastoensurethenecessaryinsulationforsignalingandelectrictraction.Specialattentionshouldbegiventothebehavioroftheconnectingbar.Ifthelatterisnotappropriatelyplacedandanchored,itmayproduceamaintenancehazardtostaffworkingonthetrack.

11.5.3.Lifetime

Thetwin-blocksleeperhasalifetimeof50years.

11.5.4.Deformabilityoftwin-blocksleepers

Figure11.6illustratesthedeformabilityoftheU31andU41twin-blocksleepersforvariousqualitiesofthesubgrade(S1,S2,S3,R),(228).Itisobservedthatdeformabilityismuchlowerthanthatoftimbersleepers.Accordingly,inthecaseofapoorqualitysubgrade,theuseoftwin-blocksleepersshouldbeaccompaniedbyanincreaseofballastthickness,whichshouldhaveadequatemechanicalstrength.

Fig.11.6.Deformabilityoftwotypesoftwin-blocksleeperforvarioussubgradequalities,(228)

11.5.5.Twinblocksleepersinhigh-speedtracks

Thetwin-blocksleeperU41(Fig.11.5)hasbeenusedinmostofthehigh-speedtracksofFrenchrailways(withVmax:300÷350km/h).However,intheParis-Strasburghigh-speedtrack(withVmax:350km/h),Frenchrailwaysusemonoblocksleepers.

11.6.Themonoblockprestressed-concretesleeper

11.6.1.Geometricalcharacteristicsandmechanicalstrength

Themonoblocksleeperhasthefollowingcharacteristics,(240):•withstandsalternatingstressesbetter,sincethestressontheconcreteisalwayscompressive,

•offersareducedsleeperheightatthecentralpart,sincethesteelbarsdonothavetobelocated,asinreinforced-concrete,asfarawayfromtheneutralaxis

aspossible,•allowsreductionofthesteelused,incomparisontothetwin-blocksleeper,•generallyislighter,comparedtothetwin-blocksleeper;thisisafact,however,whichalsoreducestransverseresistance.

Monoblocksleeperscomeinalargevarietyofgeometricalconfigurations.All,however,arecharacterizedbyareductionofthecross-sectionatthecentralpart.Figure11.7illustratesthegeometricalcharacteristicsofthemonoblocksleeperoftheBritishrailways(withinitialprestressingforce38.9tandresidualprestressingforce32.1t)andFigure11.8oftheGermanrailways(withaweightof280kg,initialprestressingforce32.5tandresidualprestressingforce27.0t),(236).Table11.1givesthegeometricalcharacteristicsofmonoblocksleepers,whichhavebeenusedinconventionaltracksbyseveralrailwaysallovertheworldandTable11.2presentsthemechanicalcharacteristicsofthemonoblocksleepersofvariousrailways,(233).AcriticalelementinmonoblocksleeperdesignistheratioλofthecriticalmomentMcr,whichthesleepercanwithstand,tothemaximummomentMmaxdevelopinginthesleeper.Thefactorinquestiontakesvaluesbetween0.7and1.8.Variationinthevalueofratioλreflectsdifferencesinthedemandsfromvariousrailways,whichinturnaredependentonthevariousconditionsofthetrackandtherollingstocktogetherwiththegeneralphilosophyofsafetyinvariouscountries.

Fig.11.7.MonoblocksleeperoftheBritishrailways,(236)

Fig.11.8.MonoblocksleeperoftheGermanrailways,(236)

Table11.1.Geometricalcharacteristicsofmonoblockprestressed-concretesleepers

usedbyvariousrailways,(233)

Table11.2.Mechanicalcharacteristicsofmonoblockprestressed-concretesleepers,

usedbyvariousrailways,(233)

ConcretemusthaveaminimumqualityC50/50,whichmeansacompressivestrengthwithin50daysof50MPa.However,forhigh-speedtracks,concretequalityrecommendedisC50/60,(230).

Steelmusthaveattheminimumatensilestrengthof1,600MPa,aleakagelimitof1,400MPa,andarelaxationlessthan3%within1,000h,(230).

Normallythebendingmomentcapacityofmonoblocksleepersiscalculatedconsideringtheprestressingforceafteralllosses(20÷25%,duetoelasticshortening,shrinkage,creepandrelaxation).Theallowableconcretetensilestressis2÷3Nt/mm2(withextremevalues0and6÷9Nt/mm2)andtheallowableconcretecompressivestressis20÷30Nt/mm2,(230).

Assleepersaresubjectedtocyclicloads,specialcaremustbetakentoensureresistanceinfatigueofallmaterialsinvolved,includingprestressedsteel.Engineersshouldaimatcrack-freesleepers,sincecracksintheconcretecausedbybendingmomentsleadtoalargeincreaseinstressvaluesoftheprestressingsteel,whichcouldcausefailureduetofatigue.Asahighqualityprestressingwireorstrandisapttowithstandastressvariationofonly5÷10%ofitsultimatestrength,mostrailwaysareconservativeintakingintoaccountconcretetensilestressesasthebasisforthemomentcapacities,andafewofthemevenexcludeanytensilestresses,(233).

11.6.2.Advantagesanddisadvantages

Monoblocksleepershaveabehaviorsimilartothatofthetwin-blocks.Theymaintainthetrackgaugeinasatisfactorymannerandhavealonglifetime.Theyrequireelasticfasteningsandspecialaccessoriesforsignaling.

However,monoblocksleepersdistributeloadsbetterthantwin-blocks,butnotaswellastimbersleepers.Theirtransverseresistanceislowerthanthatoftwin-blocks,buthighercomparedtotimbersleepers;monoblocksleepersprovidealsoagoodsurfaceforthemaintenanceinspectionstaffinchargeofinspection.

11.6.3.Lifetime

Thelifetimeofmonoblocksleepersis50years.

11.6.4.Deformabilityofmono-

blocksleepersFigure11.9illustratesthedeformabilityofamonoblocksleeperforvarioussubgradequalities(S1,S2,S3,R),(228).Itisobservedthatthemonoblocksleeperhasadeformabilitysimilartothatofthetimbersleeper,butlessflexibility.Monoblocksleepersshouldthereforebelaidonballastofsuitablethicknessandmechanicalstrength.

Fig.11.9Deformabilityofmonoblocksleeperforvariousqualitiesofthesubgrade,(228)

11.6.5.Monoblocksleepersinhigh-speedtracks

ThemonoblocksleeperillustratedinFig.11.8(knownalsoasB70)hasbeenusedinhigh-speedtracksinGermany(withVmax:250km/h).Variationsofthistypeofsleepercanwithstandhigheraxleloads(upto25tforsleepertypeB90)andhigherspeeds(upto350km/hforthetypesAl-99,Al-04usedinSpain).

However,manyhigh-speedlinesinGermany,Japan,Taiwan,Chinaandelsewherearelaidonaslabtrack(seesection17).

11.7.Manufacturing,qualitycontrolandtestingofconcrete

sleepers

Themanufacturingofbothtwin-blockandmonoblocksleepershasspecialrequirements,(233):–demandingtolerances,typically±3mmforoveralldimensionsandreinforcementlocationand±0.8mmforthepositionofcast-infasteningcomponents,

–forpre-tensionedsleepers,thedevelopmentofhighstrengthof35÷40MPainearlyages(14÷15h),

–concreteofhighdurability.Manufacturingmethodscanbeclassifiedintothreecategories,(233):

longline,forpre-tensioned,fullbondedmonoblocksleepers,shortline,forpre-tensioned,fullbondedandend-anchoredmonoblocksleepers,instantdemolding,fortwin-blockreinforcedconcreteandpost-tensionedmonoblocksleepers.

Cementshouldbeofahighqualityandaggregateswell-gradedwithaprovendurability.

Aninherentproblemofanyconstructionistoensurethatitismadefollowingthequalitiesandstrengthsspecified.Inconcretesleepers,thisrequiresaninspectionandtestingprocedurefromtheselectionandcontrolofmaterials,duringthemanufacturingprocessanduntilthepointofdelivery,(230).

Testingofconcretematerialsincludesthreestepstoconfirmacceptability:basicdesign,materialsandfinishedproduct.

TheEuropeanstandarddescribesindetailthestepsfortestingconcretesleepers:testarrangementsandprocedures,acceptancecriteria,designapprovaltests,androutinetests.

Themanufacturingrulesformonoblockconcretesleepersinclude,(230):–water/cementratio(andtolerances),–weightofeachcomponent(andtolerances),–gradingcurvesforeachaggregate,–characteristiccompressiveandtensilestrengthofconcretesamplesafter7and28days,

–maximumrelaxationforprestressingtendonsafter1,000hours,–descriptionoftheprestressingsystem,includingprestressingforceandtolerancesoneachtendon,

–methodsofconcretevibration,–curingtimeandtemperaturecycle,–methodusedforreleasingprestressingforce,–stockingandstackingrulesaftermanufacturing,–minimumconcretecompressivestrengthbeforereleasingprestressingtendons,–thepositionofthecentroidoftheprestressingtendonsshouldbewithin3mmofthetheoreticalpositionrelativetotherailseatand±6mmforeachindividualprestressingtendon.Concerningthetolerancesoftheprestressingforce,theyshouldbewithin5%ofthespecifiedforce.

Themanufacturingrulesfortwin-blockconcretesleepersinclude,(229):•water/cementratio(andtolerances),•weightofeachcomponentoftheconcrete(andtolerances),•gradingcurvesforeachaggregate,•characteristiccompressiveandtensileconcretestrength,•methodsofconcretevibration,•methodsofdemoldingandcuring,•stockingandstackingrulesaftermanufacturing.

11.8.Stressesdevelopingbeneaththesleeper

ThestressesdevelopingbeneaththesleepermaybestudiedbythesimplifiedsimulationofFigure11.10,where:

Fig.11.10.Simplifiedsleepermodel

thesleeperissimulatedasabeamprotrudingatbothends,wheelloadisassumedtobeappliedatapoint,

stressesbetweenballastandsleeperareconsidereduniformoveralength2·ℓexcbeloweachrail.However,thelastassumptionisnotaccurate.Analysisoftheeffects

occurringatthesleeper-ballastinterfaceisespeciallycomplex;itbelongstotheunilateralcontactproblemsofmechanicsandatpresentnoanalyticalresultscanbeobtained,(137),(161).

On-sitestressmeasurementsunderthesleeperhaveyieldedthestressdistributionillustratedinFigure11.11,withamaximumstressσ,givenbytheempiricalformula,(241),(242):

Fig.11.11.Stressdistributionunderthesleeper,(241)

where:α:widthofsleeper,L:lengthofsleeper,ℓexc:distancebetweensleeperend–wheelloadapplicationpoint,P:axleload,P=2·Q.

11.9.Fastenings

11.9.1.Functionalcharacteristics

Thesetofpartsandmaterialsensuringtherail-sleeperconnectionaretermedfasteningsandtheyshouldprovidethefollowingproperties:•keeptrackgaugeascloseaspossibletoitsnominalvalue,•keeptheinclinationoftherailonthesleeperconstant,•transferloadsfromtherailtothesleeper,•attenuateanddampenvibrationscausedbytraintraffic,•easyinstallationandmaintenance,•electricalinsulation,•resilienceandadequatedeflection,•avoidanceofabrasionbetweencomponentsandofover-stressing,•adequateresistancetocorrosion,•reasonablecost,•lifetimecompatibletothatofthesleeper,•resistancetovandalism.

11.9.2.Typesoffastenings

Fasteningsaredistinguishedintorigidandelasticfastenings.

11.9.2.1.Rigidfastenings

Rigidfasteningsareusedonlywithtimberorsteelsleepers.Inrigidfastenings,therailisconnectedtothesleeperwithboltsornails.Duringtrainpassagetherailcompressesthesleeperandpartofthestrainisplastic(i.e.itdoesnotdisappearwhentheloaddisappears),resultinginthecreationofagapbetweennailheadandrail.Withsuccessivetrainpassagesthegapsgrow,causingagradualslackeningofthefastening,whichaffectssafetyandmaybetheoriginofaderailment.Inadditiontoplasticstrain,highfrequencyvibrationsmayalsocontributetothewideningofthegapsandtheslackeningofthefastening.

Rigidfasteningsmaybeinstalledeitherwithorwithoutaseatingplate(Fig.11.12,11.13),thelatterbeingthepreferablesolution.

Fig.11.12.Rigidfasteningwithoutaseatingplate

Fig.11.13.Rigidfasteningwithaseatingplate

11.9.2.2.Elasticfastenings

Theuseofelasticfasteningsismandatorywithconcretesleepersandoptionalwithtimberandsteelsleepers.Twotypesofelasticfasteningsmaybedistinguished:–Screw-typeelasticfastenings,(Fig.11.14).Thesehavetheadvantageofgreatfasteningstrengthandeasymaintenanceandreplacement.Theyhavethedisadvantagethatcorrectinstallationisaffectedbylocalconditions.Screw-typesareRN,Vossloh,Nablaandotherfastenings,(Figs.11.15and11.16),(226).Thecommonelementsinallthesedesignsare,(Fig.11.14):

•athreadedelement(a),whichisusedtoapplyaforcetoaspringsteelelement,thisthreadedelementbeingremovablefromthesleeper,

•thespringsteelelement(b),whichcanbeabaroraplate,

•apad(c)betweenrailandsleepertoabsorbvibrations,toprovideasuitablelayerbetweenrailandsleeperandalsoelectricinsulation,

•insulatingelements(d)toelectricallyisolatetherailfromanymetallicpathintothesleeper.

Fig.11.14.Screw-typeelasticfastening

Fig.11.15.Vosslohfastening,(226)

Fig.11.16.Nablafastening

–Spring-typeelasticfastenings(Fig.11.17).Thesearelessadaptablethanscrew-typefastenings,butlessaffectedbyinstallationconditions,andanyerroriseasilylocatedvisually.Pandrol(Fig.11.18),Lineloc,etc.,arefasteningsofthespring-type.Thecommonelementsinspring-typefastenings(whichshouldnotrequireanysubsequentmaintenance)are,(Fig11.17):

Fig.11.17.Spring-typeelasticfastening

•someformofanchorage(a)inthesleeper,generallyatthetimethesleeperismanufactured,

•aspringsteelelement(b)togenerateclampingforcesontherailfoot,•arailpad(c)betweenrailandsleepertoattenuateforcesandstressesandtoprovideelectricalinsulation,whichisnecessaryforthesignalingsystem,

•insulatorsoralayerofinsulatingmaterials(d),toprovideelectricalinsulationbetweentherailandanymetallicpath,suchasvia(a)and(b),tothesleeper.

Fig.11.18.Pandrolfastening,(226)

11.9.2.3.Typesofelasticfastenings

Thereisagreatvarietyofelasticfastenings,Nabla,Vossloh,andPandrolbeingonlysomeofthem.Sometypesofelasticfasteningshaveaseatingplate,whereasothersdonot.Thus,elasticfasteningscanbecategorizedasfollows:–fasteningswithdirectmountingwithoutaseatingplate,–fasteningswithindirectmountingwithoutaseatingplate,–fasteningswithdirectmountingwithaseatingplate,–fasteningswithindirectmountingwithaseatingplate.

11.9.2.4.Operatingprinciplesofelasticfastenings

Duringoperation,elasticfasteningsshouldensurethefollowingprinciples,(235):•Therail-sleeperfasteningforceshouldbesufficienttomaketherail-sleeperslippageresistancemuchgreaterthantheresistancetolongitudinalmotionofthesleeperoncompletelystabilizedballast.

•Thefasteningresonancefrequencyshouldbedistinctlyhigherthantherailresonancefrequency.

•Fasteningsshouldretainsufficientclampingforceovertheyears.•Fasteningtightnessshouldbeeasilycheckedonthetrackwithoutdisassembly.•Fasteningsshouldretaintheirelasticcharacteristicsforalongtimeafterinstallation.

•Theratiooftheforceappliedontherailbase(foot)totheforcetransmittedbythefasteningstothesleepershouldbeashighaspossible.

11.9.3.Forcesandstressesinrigidandinelasticfastenings

Thedifferencebetweenrigidandelasticfasteningsbecomesapparentmainlyinthediagramofthetensileforcedevelopedinthefasteningasafunctionoftime,(Fig.11.19).Thebetterbehaviorofelasticfasteningsistherebyconfirmed.Figures11.20and11.21illustratetheforce-elongationcurvesforscrew-typeandspring-typefastenings,respectively.

Fig.11.19.Forcedevelopedinrigidandinelasticfasteningsasafunctionoftime

Fig.11.20.Force-elongationcurveforscrew-typefastenings,(226)

Fig.11.21.Force-elongationcurveforspring-typefastenings,(226)

11.9.4.Designcriteria,anchorageandinsulationofafastening

Clampingforcesvarydependingonthefasteningsystem,(Figs.11.20,11.21),andtherequirementsoftherailwayauthority.Mostfasteningsystemsofferaclampingforcewithintherange750÷1,250kgforcorrespondingelongationsof5÷15mm.Spring-typefasteningshaveagreaterelongation(forthesameforce)thanscrew-typeones.However,itisimportantforthespringtohavealargeloadcapacitybeyonditsworkingrange,asthisincreasesthelifeexpectancyofthefastening.Therailclampingforcerequirementsarecalculatedinrelationtorailprofile,permittedspeed,vehicleweight,stiffnessofthetrack,radiusofcurvature,externaltemperature,etc.

Specificcareshouldbetakenwiththeappropriateanchorageofthefastening.Forscrew-types,anchorsaremadeofnylonorpolypropyleneplastic.Forspring-types,anchorsaremadeofcastironorforgedsteel.Inadditiontoverticalforces,theanchorageshouldbedesignedtotransmitsafelysideforcesontheconcrete,(235).

Wheretrackcircuitingisusedforsignaling,insulationisanimportantrequirementforthefastening.Theinsulationrequirementsofthetrackdependonthecharacteristicsofthesignalingsystemused.Adryassemblyshouldhaveaninfiniteresistanceandawetonenotsignificantlymorethan20,000Ωperassembly.Theinsulatorshouldberesistanttowear,todegradationbyultravioletlight,andtoattacksfromtrackchemicals,(235).

11.9.5.Railcreepandanti-creepanchors

Alongfishplatedtracks(i.e.,notcontinuouswelded),ithasbeenobservedthattherails(oreventheentiretrack)aresubjectedtolongitudinalcreep.Creepusuallyoccursinthetrain’srunningdirection.Onhigh-gradienttracks,however,railstendtomovedownwards,regardlessofthedirectionoftraffic.Topreventthisslippage,specialdevices,calledanti-creepdevicesoranchors,areinstalledalongthetrack,(Fig.11.22).

Fig.11.22.Railanti-creepdevice

11.10.Resilientpads

11.10.1.Padswithorwithoutabaseplate

Asexplainedinsection7.2,Figure7.2,resilientpadsareusedbetweenrailandsleeperorbetweenrailandconcreteslab.Whenabaseplateisused(bothinballastedandnon-ballastedtracks),padsareusedbetweenbaseplateandsleeperorbetweenbaseplateandconcreteslabandarecalledbaseplatepads.

11.10.2.Functionsandpropertiesofpads

Padsmustfulfillanumberoffunctionsandproperties,(231),(237):–loaddistribution.Thepadshouldprovideloaddistributionbetweentherailfootandthesleepersoastoaccommodateirregularitiesonbothcomponents,

–vibrationattenuation.Thepadshouldattenuatethetransmittedvibrations,createdbywheelloadsandtrackirregularities,

–resilience.Thepadshouldbedesignedtoprovideoptimumdeflectioncompatiblewiththefasteningsystem,sothatthefasteningisabletoprovidethenecessaryresistancetothelongitudinalandlateralrailforcesatalltimes,

–resistancetocreep.Thepad,togetherwiththerailfasteningsystem,shouldprovideadequatecreepandtorsonialresistance,whichshouldnotchangesignificantlywithrespecttoageortonnagetransported,

–electricalinsulation.Thepadshouldhavegoodelectricalinsulationpropertiessoastoisolatetherailsfromthesleeper,thusenablingtrackcircuitingtobeusedforsignalingandcontrolpurposes,

–durability.Thepadshouldhavealifetimeofatleastaslongastherail.Theidealconditionistoinstallpadsduringrailreplacement.Furthermore,padsshouldhavepropertieswhichresistcontaminationbydirt,water,oilandchemicals,andbeabletoperformwithsimilarcharacteristicsregardlessofambienttemperaturesandweatherconditions.TheJapaneserailwayshaveexperiencedafter10yearsofoperationoftheirShinkansenhigh-speedtrainanincreaseinthepadstiffnessof66%,(237).

11.10.3.Dimensions,materialsanddesign

Thethicknessofthepad(whichvariesfrom5mmto10mm)ischosentosuittheparticularinstallationsanddependsonseveralfactors:•thewidthoftheflat-bottomedrailfoot,•thetypeofelasticfasteningused,•thesizeofthesleeperandbaseplate,ifany,•thetypeoftraffic,e.g.slow-speedheavyfreighttrafficorhigh-speedpassengertraffic.Threemaintypesofmaterialshavebeenusedforpads:

–rubber(bothnaturalandsynthetic),–plastic,–rubberbondedcork.

Thus,Frenchrailwaysuserubberpads,whilstGermanrailwaysuseaharderplasticpad.However,certainpadsareprovidedwitharoughsurfacetomoreefficientlyabsorbthedynamicandvibrationeffectsoftrainloads.

11.10.4.Force-elongationcurves

Figure11.23illustratestheforce-elongationcurveforafoamedpolyurethanepadofathicknessof7mm.

Fig.11.23.Force-elongationcurveforapadconstitutedoffoamedpolyurethaneofathicknessof7mm

11.11.RequirementsoftheEuropeanspecificationsforthesleeper-fasteningsystem

Sleepersandfastenings(togetherwithrailpads)constituteadiscretesub-systemwhichtransfersanddistributesloadsfromtherailtotheballastortheconcreteslab.AccordingtotheEuropeantechnicalspecificationsforinteroperability,(134):–sleepersshouldensuretrackgauge,equivalentconicityandtransverseresistanceofthetracktobesafelyrunatthespecificspeed,

–fasteningsshouldresistapplicationof3,000,000cyclesatthemaximumaxleloadinsuchawaythattheinitialverticalstiffnessofthetrackisnotdegradedbymorethan25%andlongitudinalrestraintbymorethan20%.Inaddition,thelongitudinalforcerequiredtocauserailslipshouldbeatleast7KN,

–forfasteningsonconcretesleepers,thedynamicstiffnessoftherailpadshouldnotexceed600MN/m,

–theminimumelectricalresistanceshouldbe5kΩ;itispermissible,however,torequirehighervaluesfortheelectricalresistanceincasesofparticularcontrol-commandandsignalingsystems.

11.12.Numericalapplicationforthedesignofthevarioustrackcomponents

Astandardgaugecontinuousweldedrailwaylinehasadailytrafficloadof30,000tons,amaximumaxleloadof20tons,amaximumspeedof140km/h,andislaidonmediumqualitysubgrade(S2).Wewillchoose:–themostsuitablerailtype,–themostsuitablesleepertype.Wewillexaminethecasesoftimber,twin-blockandmonoblocksleeper,

andfinallywewillstudy:–themostsuitabletypeoffastening,–thestressdistributionunderthesleeper.a.Therailcross-sectionwillbechosenonthebasisoftheaveragedailytrafficloadof30,000tons,accordingtoanalysisofsection10.4.1.FortimbersleeperswechooseUIC54rail,whilefortwin-blockormonoblockconcretesleeperswechooseUIC60rail.

b.Sincewehaveastandardgaugetrack,thetimbersleeperswillhavethegeometricdimensionsofFigure11.3.Iftwin-blockconcretesleepersarechosen,giventhatthisisaUIC4mediumloadlinewitharelativelylowmaximumspeed,wewillchoosethesleepertypewiththegeometricalcharacteristicsofFigure11.6.a.Wereitalinewithahighertrafficload(UICgroup1,2)andhigherspeed(V>200km/h),however,wewouldhaveselectedtwin-blocksleeperswiththegeometricalcharacteristicsofFigure11.5.Inthecaseofmonoblocksleepers,achoiceofgeometricalcharacteristicscanbemadebasedonTables11.1,11.2andFigures11.7and11.8.

c.StressdistributionunderthesleeperisillustratedinFigure11.11.Wewillcalculatethemaximumstressinthecase,forinstance,oftimbersleepers2.60mlongand0.15mwide,(Fig.11.3).Inordertotakeintoaccountthedynamiceffects(seesection8.7),thenominalstaticaxleloadwillbemultipliedbyadynamicimpactfactorof1.3,derivedfromFigure8.15forV=140km/h.Giventhatthesleeperunderloadingsupportsonly40%oftheaxleload(section8.4.8),theactualtotalloadexertedonthesleeperwillbe:20t·1.3·0.4=10.4t

Theformula(11.1),(section11.8),gives:

TheorderofmagnitudeofstressσisalsoconfirmedbyvaluesgiveninFigure7.3(section7.3).

d.Inthecaseoftimbersleepers,rigidorelasticfasteningswillbechosen,whileinthecaseoftwin-blockandmonoblocksleepers,elasticfasteningsaremandatory.Eachsleepertypehasusuallyitsappropriatetypeoffastening.Thus,fortwin-blocksleepers,Nablafasteningswillbeselected,whereasformonoblocksleeperstheVosslohorPandrol,oranothertypecompatiblewiththecharacteristicsofthesleeperwillbeselected.

12Ballast

12.1.Functionsofballastandsubballast

12.1.1.Functionsofballast

Thetermballastdenotesthelayerofcrushedstone(andonlyinexceptionalcasesofgravel)onwhichthesleepersrest.Furthermore,theballastfillsthespacebetweensleepersaswellasatsomedistance(calledballastshoulder)beyondthesleeperends.

Therailwayballast(seealsosection7.2,Figure7.1)performsseveralfunctions,suchasthefollowing:furtherdistributingstressestransmittedbythesleepers,attenuatingthegreatestpartoftrainvibrations,resistingtrackshifting(transverseandlongitudinal),facilitatingrainwaterdrainage,allowingtrackgeometrytoberathereasilyrestoredandcorrectingtrackdefects(withtheuseoftrackmaintenanceequipment,seesection16.8).Theabovefunctionsareclearlycontradictoryinsomeaspects,thusthe

ballastcannotcompletelyfulfillallofthem.Itcouldbearguedthatforgoodloadbearingcharacteristicsandaddedtrackstability,theballastneedstobewellgradedandcompactwhich,inturn,however,makesdispersalofwatermoredifficult,togetherwithassociatedmaintenance.Abalance,therefore,amongthevariousfunctionsthatballastisrequiredtoperformisaimedat.

12.1.2.Functionsofsubballast

Thegravelsubballastislaidundertheballastandhasthefollowingfunctions:–protectionoftheuppersurfaceofthesubgradefromtheintrusionofballaststones,

–furtherdistributionofstresses,

–quickrunoffofrainwater,–impartatransverseslope(commonly3÷5%)totheuppersurfaceofthesubgradeforproperrunoff.Theusualthicknessofthegravelsubballastlayeris15cm.However,some

railwaysdonotuseasubballastlayer;theysimplyuseagreaterthicknessoftheformationlayer,whichisplacedontopofthesubgrade.

12.2.Geometricalcharacteristicsofballast

12.2.1.Granulometriccomposition

Tofulfilltheabovefunctions,theballastmustbeofgoodhardstone,angularinshape(cubicorpolyhedral),withhardcorners;itmustalsohaveallitsdimensionsnearlyequalandbecleanandfreefromdust.

Theballastconsistsofamixtureofsizes,expressedaspercentagebyweight,whichshouldbeevenlygraded.

Figure12.1illustratesatypicalgranulometriccompositionofballastaccordingtoFrenchregulations.Pieceslargerthan63mmandsmallerthan16mmareacceptableupto3%aboveand2%belowthelimitvalues.ThegranulometriccompositionofballastaccordingtoBritishregulations1(14mm÷50mm)isgiveninTable12.1.

Fig.12.1.AtypicaldiagramofthegranulometriccompositionofanormalballastaccordingtoFrench

regulations,(252)

Table12.1.BallastsizeaccordingtoBritishregulations,(250)

Figure12.2illustratesthegranulometriccompositionofballastaccordingtoGermanregulations1.Piecessmallerthan22.5mmmustnotexceed3%ofweightandpiecessmallerthan31.5mm25%ofweight,(158).

Fig.12.2.GranulometriccompositionofballastaccordingtoGermanregulations,(158)

AccordingtotheEuropeanstandardforrailwayballast,(246),ballastisdesignatedbyapairofsievesizes,with31.5mmbeingthelowerlimitand50mmor63mmtheupperlimit,(Table12.2).

Table12.2.GranulometriccompositionofballastaccordingtotheEuropeanstandard,

(246)

12.2.2.Fineparticles

AccordingtotheEuropeanstandard,(246),fineparticlesaredefinedastheballastgrainspassingfromasievesizeof0.5mm.Basedonthecontentoffineparticles,variouscategoriesofballastcanbedeclared,(Table12.3),(246).

Table12.3.Categoriesofballastinrelationtofineparticlescontentaccordingtothe

Europeanstandard,(246)

12.2.3.Fines

AccordingtotheEuropeanstandard,(246),finesaredefinedastheballastgrainspassingfromasievesizeof0.063mm.Basedonthecontentoffines,variouscategoriesofballastcanbedeclared,(Table12.4),(246).

12.2.4.Particleshape

12.2.4.1.Flakinessindex

Theshapeofrailwayballastisdeterminedinrelationtotheflakinessindex,whichisdefinedasthepercentage(byweight)ofparticles,whoseleastdimensionislessthan3/5oftheirmeandimension.Basedonthevalueoftheflakinessindex,variouscategoriesofballastcanbedeclared,(Table12.5),(246).

Table12.4.CategoriesofballastinrelationtofinescontentaccordingtotheEuropean

standard,(246)

Table12.5.Categoriesofballastinrelationtotheflakinessindexaccordingtothe

Europeanstandard,(246)

12.2.4.2.Shapeindex

Theshapeofrailwayballastisdeterminedinrelationtotheshapeindex,whichisdefinedforasurfacewithLitslongestaxistobeequalto1.274·L2.Basedonthevalueoftheshapeindex,variouscategoriesofballastcanbedeclared,(Table12.6),(246).

12.2.4.3.Particlelength

Basedonthevalueofparticlelength,variouscategoriesofballastcanbedeclared,(Table12.7),(246).

Table12.6.Categoriesofballastinrelationtotheshapeindexaccordingtothe

Europeanstandard,(246)

Table12.7.Categoriesofballastinrelationtothevalueoftheparticlelengthaccording

totheEuropeanstandard,(246)

12.3.Mechanicalbehaviorofballastandsubbalast

12.3.1.Elastoplasticbehavior

On-sitemeasurementsofsettlementsandstressesatthetimeofthepassageoftrainloadshaveshownthatthemechanicalbehaviorofballastandsubballastiselastoplastic,withasmostsuitablecriterionofplasticitythecriterionofDrucker-Prager(seealsosection8.4.4.1),(148),(175).

12.3.2.Fatiguebehavior

12.3.2.1.Ballast

Bothlaboratorytestsandon-sitemeasurementshaveshownthatoninitialloading,theballastundergoesaconsiderablepermanent(plastic)deformation.Inviewofitspeculiargranulometriccomposition,theprobablecauseofthisphenomenonistherearrangementofthestonestoattainastateofequilibrium,(244),(249).Insubsequentloadings,thecontributionoftheplasticcomponenttothetotaldeformationissmaller.Triaxialtestshaveshownthattheplastic

deformation ofballastatthen-thloadingcyclemaybeexpressedasafunctionoftheplasticdeformationatthefirstloadingcycle bythefollowingformula,(253),(256):

ResearchinOREandtheBritishrailwayshassuggestedforcthevalue0.2,(256),(257).However,researchconductedbyAmericanrailwayshassuggestedforcvaluesbetween0.25and0.40,(251),(254).

Mostofthelaboratoryresultsfitwiththelinearformofequation(12.1).However,inaverysmallnumberoftests,datahaverevealedanon-linearcharacterfortheevolutionofplasticdeformationofballast,(243),(251).

Accordingtoequation(12.1)andtakingintoaccounttheaforementionedvaluesofc,itwouldtake100,000÷300,000loadingcyclestodoubletheplasticdeformationcausedinthefirstloadingcycle.

LaboratorytestsunderconstantstressconductedbytheBritishrailwayshaveyieldedthefollowingsemi-empiricalformulafortheplasticdeformation ofballastafterNloadingcycles,(257):

where:n:ballastporosity,a:coefficientdependingonthelevelofthestressapplied.Ittakesvaluesbetween1and2forlowstresses,butmayreachthevalue3forhighstresses.

12.3.2.2.Subballast

ForgravelsubballastthefollowingformulahasbeensuggestedforthetotaldeformationafterNloadingcycles,

where::deformationattheN-thloadingcycle,:deformationatthefirstloadingcycle,

α:aparameterdependingonthecharacteristicsofgravel.

12.3.3.Modulusofelasticity

12.3.3.1.Ballast

Withrespecttothemodulusofelasticity,triaxialtestshaveshownittochangeduringthefirst1,000loadingcyclesandthereaftertoremainaboutconstant,(Fig.12.3).Thisissimilarlyexplainedaswiththeappearanceofimportantplasticdeformationsduringthefirstloadingcycle.Themodulusofelasticityattheone-thousandthloadingcyclewasfoundtobeaboutdoublethatatthefirstcycle,E1,0002·E1,(249),(255).

Fig.12.3.Evolutionofelasticdeformationofballastinrelationtothenumberofloadingcycles,(149)

12.3.3.2.Subballast

Concerninggravelsubballast,aseriesoftestshavesuggestedthatthemodulusofelasticitydoesnotchangeinrelationtothenumberofloadingcycles,(256).

12.4.Ballasthardness

Ballastmusthaveadequatehardness,otherwiseitdisintegratesandcannotfulfillitsfunctions.BallasthardnessisdeterminedbytheDeval,theLosAngelesandtheMicrodevallaboratorytests.

12.4.1.TheDevaltest

Thisistheoldestofthetestsstillinuse.Itwasdesignedin1896,atatimewhenroadtrafficwascomposedofcarriageswithwheelssurroundedbysteelhoops(tires).

Theweightofthetestsample(asclosetocubicshapeaspossible)is5kg.InthecaseoftheDevalstandardtest,knownalsoasDevaldrytest,thesamplepiecesarewashedanddriedbeforebeingweighed.TheyarethereafterplacedinthecylindersoftheDevalmachine,whichhaveaninternaldiameterof20cm,aninternallengthof34cm,areinclinedby30°,andareconnectedtoahorizontal

axle,(Fig.12.3).Themachineisthenstarted(2,000revolutionsperhour)andtheentiretesttakesabout5hours(atotalof10,000revolutions).

LetAbetheinitialweightofthesampleandBtheweightofthesamplematerialretainedafterthetestbyasieveofadiameterd(mm).ThevalueofdisaccordingtoFrenchregulations1.6mmandaccordingtoBritishregulations2.36mm,(250),(252).Hence,thepercentageofattritionwillbe:

TheDevalcoefficientQisderivedfromtheformula:

Fig.12.4.Devalattritionmachine

SomeregulationsspecifythattheballastshouldhaveaDevalcoefficientgreaterthan14inthecaseofhardrockandgreaterthan12inthecaseoflimestonerock.However,otherregulationsrequireagreaterhardnessforballast

andtheyspecifythattheDevalcoefficientbegraterthan16.Ifthisvalueistakenintoaccount,ballastfromlimestonerockmayproveinappropriateandrailwayauthoritiesshouldlookforaballastcomingfromgraniterock.

TheattritionactionduringthecourseoftheDevaltest(thesamplecompletes10,000revolutionsattheendofthetest)ismuchstrongerthanthevibratingaction.Therefore,onlyverysoftrockisbrokentoaconsiderableextent.Pieceswithsharpcornersinparticularareroundedoff.

AnothervariationoftheDevalstandardtestistocarryoutthewholeprocedureinthepresenceofwater,inwhichcasetheresultistermedasthewetDevalcoefficient.

12.4.2.TheLosAngelestest

IntheLosAngelestest(designedin1926),thetestequipmentconsistsofasteelcylinderwithaninternaldiameterof71.1cmandaninternallengthof50.8cm.A5kgsampleisplacedinsidethecylindertogetherwith12steelballs,eachoneweighing420gr.Thecylinderisthensetinrotation(30÷33roundsperminute)until500revolutionsarecompleted(durationofthetestisabout15minutes).

LetAbetheinitialweightofthesampleandBtheweightofthesamplematerialretainedafterthetestbyasieveofadiameterd(mm)(d=1.6mmaccordingtoFrenchregulationsandd=2.36mmaccordingtoBritishregulations).ThepercentageofattritioniscalledtheLosAngelescoefficientandis:

ManyregulationsspecifythattheballastmusthaveaLosAngelescoefficientsmallerthan25.

TheLosAngelestesthasthefollowingcharacteristics:–actionontheinertmaterialissufficientlystrongtobringoutanyweaknesses,–itisequallysuitablefortestinginertmaterials,crushedrockandgravel,–thetimerequiredtocompletethetestisshort,–theresultsofthetestagreetoasatisfactorydegreewiththebehaviorofthecrushedandinertmaterialsinvariousconstructionprojects.

ManycurrenttechnicalregulationsarebasedontheLosAngelestest.SeveralvariationsoftheLosAngelestestareinuse.

AccordingtotheEuropeanstandardforballast,theLosAngelestestmethodshouldbethereferencetestforthedeterminationofballasthardness,(246).

BasedonthevalueofLosAngelescoefficient,variouscategoriesofballast

canbedeclared,(Table12.8),(246).

Table12.8.CategoriesofballastinrelationtotheLosAngelescoefficient,accordingto

theEuropeanstandard,(246)

However,itshouldbeemphasizedthataccordingtotheEuropeanstandard,thesampleintheLosAngelestestis10kgandthemachineisrotatedfor1,000revolutionsataspeedof31÷33roundsperminute.

12.4.3.TheMicrodevaltest

TheMicrodevaltestisusedprincipallytodeterminethehardnessofgravelsubballast.Thetestequipmentconsistsofacylinderofalengthof154mmwithaninternaldiameterof200mm.Thesampleconsistsof500grofgravelwithgrainsrangingbetweensievediameters10mmand14mm.Asteelballweighing5kgand2.5litersofwaterareputinthecylindertogetherwiththesample.Thecylinderperforms12,000revolutionsataspeedof100revolutions/minute.Letbemthemass(ingr),afterthetest,ofgrainssmallerthanthe1.6mmsieve.TheMicrodevalcoefficientMDEisdefinedas

TheEuropeanstandardsuggestsuseoftheMicrodevaltestwhenrequired.BasedonthevalueoftheMicrodevaltest,variouscategoriesofballastcanbedeclared,(Table12.9),(246).

However,itshouldbeemphasizedthataccordingtotheEuropeanstandard,thesampleintheMicrodevaltestis10kgandthemachineisrotatedfor14,000revolutions.

12.4.4.Requiredstrengthandhardnessofballast

Therequiredstrengthandhardnessofballastdependuponthelinetraffic,thefrequencyofrenewalofballast(usuallyevery15÷20years),thematerialofthecrushedstone,etc.FrenchregulationsmandatethattheLosAngelesandDevalcoefficientsintersectatapointlyingwithinthebandspecifiedinFigure12.5,(252).

Table12.9.CategoriesofballastinrelationtotheMicrodevalcoefficient,accordingto

theEuropeanstandard,(246)

Fig.12.5.CombinationoftheLosAngelesandDevalcoefficientsforballastaccordingtoFrenchregulations,(252)

12.5.Determinationoftheappropriatethicknessofballast

12.5.1.Determinationoftheappropriatethicknessoftrackbed

Untilthemid-1980s,ballastthicknesswascalculatedbasedontheBoussinesqequations.However,amoreaccurateanalysis,byusingthefiniteelementmethod,hasallowedallrailwayparametersconcerningballastdimensioningtobetakenintoaccount:•qualityofsoilandbearingcapacityofthesubgrade,•typeofsleeper,•trafficcharacteristics(trafficloadandaxleload),•volumeofmaintenanceworks,•trainspeed,

•useornotofageotextile.

Thicknesseoftrackbedstructures(e=ballast+subballast)willbederivedfromstressanalysisgiveninFigure8.7ofsection8.4.7andiscalculatedbythefollowingformula,whichissuggestedbytheUIC,(146),(186):

where:N(parameterdependingonsubgradequality):–0.70mforsubgradeofbadquality(S1),–0.55mforsubgradeofmediumquality(S2),–0.45mforsubgradeofgoodquality(S3).a(parameterdependingontrafficload):–0forUICgroups1and2orfortrackswithV>160km/hirrespectiveoftheUICgroup,–-0.05mforUICgroups3and4,–-0.10mforUICgroup5,–-0.15mforUICgroup6,b(parameterdependingonsleepertype):–0fortimbersleeper(withalengthL=2.60m),–(2.50-L(m))/2forconcretesleepersoflengthL(bmaybenegativeforL>2.50m),c(parameterdependingonthevolumeoftrackmaintenanceworks):–0foramediumvolumeoftrackmaintenanceworks,–-0.10mforahighvolumeoftrackmaintenanceworksandgroupsUICfrom1to5,–-0.05mforahighvolumeoftrackmaintenanceworksandgroupUIC6,d(parameterdependingonthevalueofaxleloadQ):–0forQ=20.0tons,–0.05mforQ=22.5tons,–0.12mforQ=25.0tons,–0.25mforQ=30.0tons,f(parameterdependingontrainspeed):–0forV<160km/handsubgradequalitiesS1,S2,–0forhigh-speedtracksonsubgradequalityS3,

–0.05mforhigh-speedtracksonsubgradequalityS2,–0.10mforhigh-speedtracksonsubgradequalityS1,g(parameterdependingontheuseofageotextile):–geotextilethickness,–0whenageotextileisnotused.

12.5.2.Requiredthicknessoftrackbed(ballast+subballast)toavoidfrostpenetration

ThechartofFigure12.6wascompiledfromboththeoreticalandexperimentalstudies,whichenabledthecalculationofthethicknessofballast+subballastinrelationtothefrostindex,(seesection9.11),inordertoavoidfrostpenetrationinthesubgrade.TheshadedareaofFigure12.6representsconditionsencounteredinnorthernEuropeorinareaswithdifficultandlastingwinters.

12.5.3.Thicknessofballastandsubballast

Gravelsubballastusuallyhasathicknessof15cm.Itshouldbewell-gradedandhavethefollowingmechanicalcharacteristics:Microdevalcoefficient<15or20LosAngelescoefficient<20or25

dependingontheimportanceoftheline.

However,somerailwaysrequire,particularlyonnewlines,thegravelsubballasttocontainatleast30%ofcrushedstone,(186).

Thethicknessofballastiscalculatedbysubtractingthethicknessofthesubballast(usually15cm)fromthethicknessofthetrackbed,ascalculatedpreviously.

12.5.4.CalculationofthicknessofballastaccordingtotheBritishregulations

ThethicknessofballastiscalculatedaccordingtoBritishregulationsinrelationtothespeedandtonnageoftheline,asshowninTable12.10.

Fig.12.6.Requiredthicknessofballast+subballasttoavoidfrostpenetrationinthesubgrade,(186)

Table12.10.ThicknessofballastaccordingtoBritishregulations,(141),(250)

12.5.5.Numericalapplication

WewillconsideratrackofUICgroup4,withadailytrafficrangingfrom20to40thousandtons,whichisrepresentativeofagreatnumberoftracksalloverthe

world.Thetrackislaidonmonoblockprestressed-concretesleeperswithalengthL=2.60m.Subgradesoilisofmediumquality(S2),axleloadis20tonsandthevolumeofmaintenanceworksisconsideredalsoofmediumlevel.Maximumtrainspeedis200km/handageotextileofathicknessof5mmisplacedontopofthesubgrade.

Thicknesseoftrackbedstructureswillbecalculatedaccordingtoformula(12.8),

e(m)=N(m)+a(m)+b(m)+c(m)+d(m)+f(m)+g(m)

withthevariousparameterstakingthefollowingvalues:N=0.55m(subgradequality:S2),a=-0.05m(trackofUICgroup4),b=(2.50m-2.60m)/2=-0.05m(sleeperswithalengthL=2.60m),c=0(trackwithamediumlevelofmaintenanceworks),d=0(axleload:20tons),f=0.05m(high-speedtrackonsubgradequalityS2),g=0.005m(thicknessofgeotextile).

Substitutingthesevaluesintheaboveformula,wecalculatethethicknesseofthetrackbed(ballast+subballast):

e(m)=0.55-0.05-0.05+0.0+0.0+0.05+0.005=0.505m

Subballastwillbegiventheusualthicknessof0.15m,thusthethicknessofballastwillbe:e-0.15m=0.355m.

Itistonotethatthisvalueofballastthickness(calculatedaccordingtoformula(12.8))isveryclosetothevaluessuggestedbyBritishregulations(=0.38m).

Ifthetrackislaidinareaswithcoldwhether,thethicknessofthetrackbedshouldbecalculatedtoensurefrostprotectionofthesubgrade.Supposeanaverageannualtemperatureof6°Candthatfor100daysperyearnegativetemperatureis-3°C.Thus,thefrostindexwillbe:100×3=300degrees×days.

FromFigure12.5wededucethat,inordertoavoidfrostpenetration,thethicknesse(ballast+subballast)shallbe0.80m,fargreaterthanthevaluecalculatedaccordingtothemechanicalrequirementsofthetrack.Itisobviousthatinthiscasethegreatervalueofballast+subballastwillfinallybetakenintoaccountforthedimensioningofthetrackbed.

12.5.6.Appropriatethicknessofballastformetricgaugetracks

Formetricgaugetracks,recommendedvalues,accordingtoUIC,fortheappropriatethicknessoftheballastaregiveninTable12.11,(140).

Table12.11.Appropriatethicknessofballastformetricgaugetracks,(140)

12.6.Trackcross-sections

Inthepresentandpreviouschaptersweanalyzedhowdimensioningandmechanicalcharacteristicsofthevariouscomponentsofthetrackshouldbecalculated.Alltheseanalysesareusuallyreflectedinsummaryinthetrackcross-section,whichillustratesdimensionsofallcomponentsofthetracksystem.

Designofatrackcross-sectiondependsonthefollowing:whethertrackissingleordouble,thedistancebbetweenthetwotracks,whichdependsontrainspeed.Asexplainedinsection7.10.3,thedistancebrangesbetween3.60m÷4.00mforV<200km/h,between4.00m÷4.70mforV=200÷300km/handcantakethevalueb=4.80mforV=350km/h.Infigurespresentedbelow(Figs.12.7to12.15),wecanremarkthatforthesamevalueofb,variousrailwaysapplydifferentvaluesofthepermittedmaximumspeed.Thisisprincipallyrelatedtowhetherornotthereisagreatnumberoftunnelsinthespecifictrack,thelengthoftheballastshoulder,whetherasuperelevationoftheballastshoulderisgivenornot,whetherthetrackiselectrifiedornot,whetherwiresofsignalingsystemsareplacedwithinoroutsidethetrack,onthewidthofrollingstock.

Somerepresentativecross-sectionsoftracksareillustratedbelow:•singletrackwithsteelortimbersleepers,(Fig.12.7),•singletrackwithtwin-blockreinforced-concretesleepers,(Fig.12.8),

•doubletrackwithmonoblockprestressed-concretesleepersandadistancebetweentracksb=4.20m(trackappropriateforspeedsupto250km/h).Casesofstraighttrack(Fig.12.9)andcurvedtrack(Fig.12.10)aregiven,

•high-speedParis-LyonstrackofFrenchrailways(Vmax=300km/h),(Fig.12.11),

•high-speedParis-MarseilletrackofFrenchrailways(Vmax=350km/h),(Fig.12.12),

•high-speedtrackofGermanrailways(Vmax=300km/h),(Fig.12.13),•high-speedtrackofItalianrailways(Vmax=250km/h),(Fig.12.14),•high-speedtrackofJapaneserailways(Vmax=300km/h),(Fig.12.15).

Fig.12.7.Cross-sectionofasingletrackwithsteelsleepers

Fig.12.8.Cross-sectionofasingletrackwithtwin-blocksleepers

Fig.12.9.Cross-sectionofadoubletrackwithmonoblockprestressed-concretesleepers(Vmax=250km/h),(straighttrack)

Fig.12.10.Cross-sectionofadoubletrackwithmonoblockprestressed-concretesleepers(Vmax=250km/h),(curvedtrack)

Fig.12.11.Cross-sectionofthehigh-speedParis-LyonstrackofFrenchrailways(Vmax=300km/h)

Fig.12.12.Cross-sectionofthehigh-speedParis-MarseilletrackofFrenchrailways(Vmax=350km/h)

Fig.12.13.Cross-sectionofahigh-speedtrackofGermanrailways(Vmax=300km/h)

Fig.12.14.Cross-sectionofahigh-speedtrackofItalianrailways(Vmax=250km/h)

Fig.12.15.Cross-sectionofahigh-speedtrackofJapaneserailways(Vmax=320km/h)

12.7.Lifetimeandre-useofballast

Itissuggestedthatthelifetimeofballast,sleepersandrailsshouldbecombined,sothattheyareallreplacedduringthesamerenewalofthetrack.Inhigh-speedtracks,ballastrenewalisdoneonceper15÷20years,whereasconcretesleepersandrailshavealifetimeofapproximately50years.

However,andduetofatigue,ballaststonescansupportonlyalimitednumberofmaintenancesessions,duringwhichballastreceivesforcesofhigh

intensity.Thelifetimeofballastcanbeincreasedbyusingstonesofgreaterhardness,

bymakingthewidthofballastlayergreaterandbyrealizingamorehomogeneouscompactingoftheballastlayer.SuchmeasureshaveresultedinSwitzerlandinanincreaseofthetimebetweensuccessivemaintenancesessionsfrom4to7yearsandinadecreaseofmaintenanceexpensesof40%within10years,(247).

Ballasttakenfromatrackduringmaintenanceisapollutedmaterial(particularlyinthecaseoftimbersleepers(whichareimpregnatedwithspecialfluids),withamassof1.7t/m3,insteadofamassof1.5t/m3foranewballast.Ifthisballasthassufficientremainingmechanicalresistances,thenitcanbewashedandre-usedassubballastorasformationlayerduringtherenewalofsecondarylines.

Iftheremainingresistancesofballastareevenhigher,thenafteramechanicaltreatmentandwashing,itcanbeusedasballastforsecondarylines(V<140km/h).Agreatpartofballast(900,000tonsofballastperyeararetakenoutoftracksduringmaintenanceinFrance)isinthiswayre-usedinFrance,Germanyandelsewhere,(247).

Re-useofballastisnotapurelytechnicalproblem;theenvironmentalandeconomicaspectsshouldalsobetakenintoaccount.Thecostofthere-useofballastshouldbecomparedtothecostofnewballast(around10€/toninWesternEurope)andtothecostoftransportofneworre-usedballasttoitsfinalareaofuse.However,costsofdisposaloftheusedballast(whichmaybeashighas60€/ton,dependingonthecountry)mayrenderthere-useoftheballastcostbeneficial.

1Britishrailwaysoperatedasaunifiedrailwayenterpriseresponsibleforbothinfrastructureandoperationuntilthemid-1990s.SincethattimeresponsibilityforinfrastructurehasbeengiventoRailtrackandlatertoRailNetwork.WheneverthetermBritishregulationsisusedinthisbook,itincludesregulationsnotonlyofformerBritishrailwaysbutofRailtrackandRailNetworkalso.

1Toavoidanyconfusion,itisworthrememberingthedifferencebetweenregulations,specifications,codes,standardsandguidelines.Regulationsandspecificationsarerulesissuedbygovernmentalorinter-governmentalbodiesthatimposespecificinstructionsormethods.Codesareaformoflegislationwhichdefinesaprocedureorperformancetobefollowed.Standardsareuniformcriteriaandmethodsdevelopedbyanationalorinternationalregulatorybodyandrepresentsuggested(butnotobligatory)requirements.Guidelinesarenon-mandatorysuggestionsandrecommendations.

13TransverseEffects–Derailment

13.1.Transverseeffects

Whenarailvehiclerunsonthetrack,vertical,transverseandlongitudinalforcesaredevelopedontherailwaysystem,(seesection7.11.1).Uptothischapter,wehavefocusedontheeffectsofverticalforces,whichdeterminethedimensioningofthevariouscomponentsoftherailwaytrackandthesubgrade.Transverseforcesaffectbothpassengercomfortandtrainsafety.Exceedingthelimitsoftransversetrackresistancemaycausetrackshiftingandeventualderailment.Derailmentmayalsobetheresultofeitherwheelclimbingontherailorofvehicleoverturning,(261).Speedincreasesinrecentyearshavemandatedadditionalstrictprotectivemeasurestoincreaseandensuresafety.Itshouldbestressedthatcomparedtoothermeansoftransportation,railwaysarethesafest,(seesection1.2.3).

13.2.Transversetrackforces

Letusfirstinvestigatewhattransverseforcesareappliedduringtrainmotiononthetrackasawhole.Transverseforcesarecomposedofonestaticandonedynamiccomponent.

13.2.1.Transversestaticforce

Thisisdefinedastheforceduetothenon-compensatedcentrifugalaccelerationandtodrivingforcesoncurves.TransversestaticforceHs(t)willbecalculatedbythefollowingsemi-empiricalformula,(269):

where:P:axleload,NT:transversedefect,(seesection16.4.2),ifthetrainisonastraighttrack

orcantdeficiencyhdmax,(seesection14.2.2),ifthetrainisonacurve.

13.2.2.Transversedynamicforce

Thisisdefinedastheforcecausedbythevariousformsoftrackdefectsandbyrollingstockdefects.ThetransversedynamicforceHd(t)willbecalculatedbythefollowingsemi-empiricalformula,(269):

where:P:axleload,V:trainspeed.

13.3.Transversetrackresistance

Transverseresistanceofthetrackdependsonthesleepertypeandontrackmaintenance.Wewillconsidertheworstcase,i.e.atrackimmediatelyaftermaintenance,whichdestabilizesthetrack.Undertheinfluenceofrailtraffic,theballastiscompacted,thusresultinginanincreaseofthetransverseresistance.

Onatrackwithtimbersleepers,forwhichmaintenanceisperformedbynon-mechanical(manual)means,thetransverseresistanceiscalculatedbytheformula,(267):

Ontrackswithtimbersleepers,forwhichmaintenanceisperformedmechanically,thetransverseresistanceiscalculatedbytheformula:

Ontrackswithtwin-blockreinforced-concretesleepers,forwhichmaintenancebymechanicalmeansismandatory,thetransverseresistanceis:

Fortrackswithmonoblockprestressed-concretesleepers,suchananalyticalformulaisnotavailable;however,testshaveshownthattheconstanttermofequations(13.4)and(13.5)hasinthecaseofmonoblockprestressed-concrete

sleepersvaluesbetween1.0and1.5,(269).Theaboveformulasaresemi-empiricalandaretheresultofaseriesoftests

conductedbytheFrenchandGermanrailways,(267),(269).Mostrailwayauthoritiesarecurrentlyusingthemandnoobjectionsorreservationshavebeenexpressed.

Researchontheeffectsofspeedontransversetrackresistancehasshownthatthelatterisnotaffectedbyanincreaseofspeed,(267).

Theaboveformulasareapplicableprovidedthatadditionaldynamicloads(seesection8.6)arenotgreaterthan20%ofnominalstaticload.If,however,theadditionaldynamicloadsexceed20%ofstaticload,theaboveformulasshouldbemultipliedbyacorrectionfactorintheorderof0.9.Thisappliesalsototracksofmediumorbadquality,(265).

13.4.Influenceofballastcharacteristicsontransversetrackresistance

13.4.1.Influenceofthegeometricalcharacteristicsoftheballastcross-section

Transversetrackresistanceistheresultantofthefollowingthreecomponents:Acomponentgeneratedbyfrictiononthelowersurfaceofthesleeper,proportionaltosleeperweight.Acomponentresultingfromfrictionbetweenthesleepersidesandtheballastfillingthespacebetweenconsecutivesleepers.Thiscomponentdependsonthedegreetowhichthespacesbetweensleepersarefilled,(Fig.13.1),aswellasonthedegreeofballastcompacting.Thislateralcomponentamountstoabout40÷50%ofthetotalresistanceinthecaseoftimbersleepers,15÷25%inthecaseoftwin-blockreinforced-concretesleepers,and30%inthecaseofmonoblockprestressed-concretesleepers,(268).Acomponentdevelopedatthetwoendsofthesleeperanddependingbothonthewidthofballastshouldercandwhethertheballastissuperelevatedornot,(Fig.13.2).

Fig.13.1.Influenceontransversetrackresistanceofthedegreeofballastfillingbetweensleepers,(268)

Fig.13.2.Sleeperend,ballastshoulderwidthcandballastsuperelevationh

Figure13.3illustratestheincreaseoftransverseresistancecausedbyanincreaseofballastwidthbeyondsleeperendsaswellasbyasuperelevationoftheballastsection.Therefore,anincreaseoftheballastwidthcombinedwithasimultaneoussuperelevationispreferabletoasimpleincreaseofwidth.

Theeffectoftheslopeoftheballastcross-sectiontotransverseresistanceissecondary,(268).

Fig.13.3.Correlationoftransversetrackresistancewiththegeometricalcharacteristicsoftheballastcross-section,(268)

13.4.2.Influenceofthegranulometriccompositionofballast

Theshapeandsizeoftheballaststones,theirgranulometriccomposition,andthehardnessofthematerialallhaveaconsiderableinfluenceontransversetrackresistance,(Fig.13.4).

13.4.3.Influenceofthedegreeofballastcompacting

Aftertrackmaintenanceworks*,thetracklosesitstransverseresistancetoaconsiderabledegree,(Fig.13.5).Inordertorecovertransverseresistance,itisnecessarytocompacttheballast.

Transversetrackresistanceisalmostfullyrecoveredafterthepassageofacertainamountoftraffic,inparticularafterthepassageof2milliontons,(Fig.13.6).

Fig.13.4.Influenceofthegranulometriccompositionofballastontransversetrackresistance,(268)

Fig.13.5.Trackstabilizationforvariousformsofcompacting,(268)

Fig.13.6.Recoveryoftransversetrackresistance,aftermaintenance,asafunctionoftrafficload,(261)

13.5.Influenceofsleepertypeontransversetrackresistance

Aseriesofexperimentaltestsonfullystabilizedtrackshaveshowntheunquestionablesuperiorityofconcretesleepers,especiallytwin-block,(262).Figure13.7illustratesthetransverseresistanceforvarioussleepertypes.Therelativelylargespreadisattributabletomanufacturingvariations(dimensions,weight,sleeperform,etc.)aswellastoballastqualityandproperties.

Thehightransverseresistanceoftwin-blocksleepers,morethandoublethatoftimbersleepers,ismainlyduetothefollowingtwofactors,(258):Duetothegreaterweightoftwin-blocksleepers,thetransverseresistancecomponentcorrespondingtothefrictionbetweenthelowersurfaceofthesleeperandtheballastisgreater.Thetransverseresistancecomponentgeneratedatthesleeperendsismuchgreater.

Fig.13.7.Influenceofsleepertypeontransversetrackresistance,(262)

Comparedtotwin-blocksleepers,thetransverseresistanceoftrackswithmonoblocksleepersissmaller,butclearlyhigherthanthatwithtimbersleepers.Thisisduetothegreaterweight,thegreaterheightandthelargercontactsurfaceofmonoblocksleepers.

Theincreaseofsleeperlengthfrom2.40mto2.60mintheGermanrailwayshasresultedinanincreaseoftransverseresistanceby15÷20%,(268).

Thetransverseresistanceofsteelsleepersdependstoacertaindegreeuponthesleepershape(curvatureattheends,ballastcontainedinthesleeper,etc.).However,thetransverseresistanceofsteelsleepershasvaluessimilartothoseoftimbersleepers,(Fig.13.7).

Concerningtimbersleepers,acomparisonbetweenthevariousqualitiesoftimberleadstothefollowing:–Differencesbetweensleepersmadeofhardtimber(e.g.oak)andthosemadeofsofttimber(e.g.pine)areminor.Sleepersplacedalongtimeago,withsurfacesroughenedbytheballast,especiallyifthelatterhasbeensubjectedtocompaction,presentatransverseresistanceslightlyhigherthannew(unused)sleepers.

–Sleepersmadeoftropicaltimber,duetotheirgreathardnessandsmoothsurfaces,haveatransverseresistancereducedby15%,comparedtootherqualitiesoftimber,(268).

–Areductionofsleeperspacingleadstoaslightreductioninthevalueofthetransverseresistancepersleeper,which,however,ismorethanoffsetbythegreaternumberofsleepersperkilometer.Overall,transversetrackresistanceincreaseswhensleeperspacingdecreases,(Fig.13.8).

Fig.13.8.Transversetrackresistanceasafunctionofsleeperspacing,(268)

13.6.Additionalmeasuresandspecialequipmentusedtoincreasetransversetrackresistance

Incertaincases(e.g.smallradiusofcurvature,turnouts,bridges,etc.),itisnecessarytoincreaselocallytransversetrackresistancebyspecialmeasures,whichdonotentailalargeexpense,suchasaspecialsleepershape,roughenedseatingsurfaces,transverseanchors,etc.

Theproblemisencounteredincertainmountainousrailwaytracks,whichhaveverysmallradiusofcurvatureandneedahightransversetrackresistancetoovercomehighcentrifugalforcesandinternalstressesinrails.Rougheningthesideandbottomsurfacesoftimbersleepersincreasestransverseresistanceonlyslightly.Incontrast,cuttinggroovesintotheseatingsurfaceoftropicalorigintimbersleepersresultsinanincreaseoftransverseresistanceby20÷25%,(268).

Thegrooves,however,shouldhavesufficientwidthanddepthsoastoensurethatthesleepersgriptheballastwell,(Fig.13.9).

Fig.13.9.Groovescutintotheseatingsurfaceoftimbersleepersinordertoincreasetransverseresistance,(261)

Aconsiderableincreaseoftransverseresistance(20÷80%)maybeachievedbyso-calledtransverseanchors,(Fig.13.10),(261).Anevengreaterincrease(intheorderof170%)isattainedbyplacingconcretepostsagainstsleeperends.Thisisanexpensivesolution,whichinadditioninterfereswithtrackmaintenanceconductedwiththeuseofmechanicalequipment,(268)

Fig.13.10.Anchorsforincreaseoftransversetrackresistance,(261)

13.7.Derailment

Thederailmentofarailvehiclemayoccurasaresultofoneofthefollowing,(261),(266):trackshifting,wheelclimbingontherail,vehicleoverturning.

Wewilldiscusseachcaseseparately.

13.7.1.Derailmentcausedbytrackshifting

Undertheinfluenceofconsiderabletransverseforces,thetrackshiftsasawholeandcausesderailmentofthevehicle.Thisformofderailmentmainlyoccursathighspeeds.TheconditionforderailmentbytrackshiftingisthatthetransverseforceH,(Fig.13.11),whichmaycausetrackshifting,exceedsthetransversetrackresistanceL,givenbyformulas(13.3)to(13.5),(section13.3):

Fig.13.11.Verticalandtransverseforcesonawheel

where

13.7.2.Derailmentcausedbywheelclimbingontherail

WhenthetransverseforceYdevelopedbetweenwheelandrailexceedsacertainvalue,thenthewheelclimbsontherailandcausesderailment.ThisformofderailmentoccursmainlyatlowspeedsandtheconditiontoavoidderailmentisgivenbyNadal’sformula,(Fig.13.12):

where:β:therail-wheel(flange)angle,f:therail-wheelfrictioncoefficient.

Fig.13.12.Verticalandtransverseforcesbetweenwheelandrail

Studiesofvariouscasesofderailmenthaveshownthatequation(13.8)canbesimplifiedasfollows,(147),(269):

vehicleonaxles: ,vehicleonbogies:

Inequations(13.9),YandQarethetotalexertedforces.TothestaticloadQshouldthereforebeaddedthedynamicloads(seesection7.11.2andsection8.6),whichmayaugmentthenominalvalueofQ(e.g.10t/wheel)byupto50%.WithrespecttothetransverseforceYbetweenwheelandrail,itisofastronglystochastic1natureandnoanalyticalformulationofYasafunctionoftherollingstockandtrackparametersisavailable.TheonlywaytocalculatevaluesofYisbyon-sitemeasurementsontherail,which,however,aredifficult,notveryreliable,andofcoursethesiteofameasurementcannotbeexpectedtocoincidewithalikelyderailmentsite.

CalculationoftheforceYmaybeobtainedbyconsideringforcesatbothrails.Infact,equation(13.8)appliesusuallyattheouterrail.However,forcesattheinnerrailmaybetakenintoconsideration.Inthiscasewewillhave:

withγ2beingtheconicaltread.

Equations(13.10),(13.11),(13.12)permitthecalculationoftransverseforcesY1,Y2attheouterandinnerrail.

Fromaseriesofderailmentaccidents,(263),(264),itwasderivedthatthereisahighriskofwheelclimbingonarailwhentheangleβbetweenwheelandrail,(seeFig.13.12),attainscriticalvaluesfrom58°(caseofawetorlubricatedrail,f=0.10÷0.12)to70°(caseofadryrail,f=0.25÷0.30).

However,thewheelclimbingontherailismostlikelytooccurwhenavehicleisstartingfromrestonasharpcurvewithahighcant,dryrailsandanunlubricatedandbadlyside-wornhighrail.Thereasonsforthisare,(260):thevalueofQontheouterrailisminimizedbywheelweighttransfer,duetocantexcess,transverseforceYisinthiscasethegaugespreadingforce,whichisrelatedtothewheelweightontheinnerrail(maximizedbycantexcess)andthecoefficientoffrictionacrosstheinnerrail(maximizedbythedryrailandstartingconditions),thewheel-railfrictioncoefficientismaximizedbythelackoflubricationandthestartingcondition,theangleβisreducedbytheside-wornrailcondition.

13.7.3.Derailmentcausedbytheoverturningofthevehicle

Inthiscase,thevehiclecapsizesduetooverallunstableequilibrium.Itwasfoundthatintheworstcase(withthecenterofgravityelevatedat2.25mfromthetrack)forstandardgaugetracks,avehiclewouldoverturnwhenthetransverseaccelerationreachesg/3,(269).

Asexplainedinsection14.3,tracksarelaidforamaximumvalueofnon-compensatedcentrifugalaccelerationrangingbetween0.5÷1.0m/sec2andneverexceedingamaximumvalueof1.0m/sec2g/10.Therefore,thesafetyfactoragainstderailmentbyoverturningwillhaveasalowervalue .

13.7.4.Derailmentsafetyfactor–Numericalapplication

Wewillinvestigatethederailmentsafetyfactorforatrainwithvehiclesonbogiesmovingonacurvewithacantdeficiencyhd=100mm(seesection14.3,Table14.1)ataspeedof120km/h.Thevalueofaxleloadis20t;thetrackislaidontwin-blocksleepersandismaintainedwithmechanicalequipment.Thewheel-railfrictioncoefficientisf=0.30(caseofadryrail).

a.Derailmentbytrackshifting

Accordingtoequation(13.6),derailmentbytrackshiftingwilloccurwhentransversetrackforcesexceedtransversetrackresistance,i.e.whenH>L.SinceH=Hs+Hd,fromequations(13.1)and(13.2)itfollowsthat:

Aswestudythecaseofderailmentonacurve,theparameterNTofequation(13.1)hasbeentakenequaltothelimitcantdeficiencyvaluehdmax(seesection14.2.2,equation(14.13)andsection14.3,table14.1).

Transversetrackresistanceiscalculatedbyequation(13.5):

Thesafetyfactoragainstderailmentforthisparticularcasewillbe

b.Derailmentbywheelclimbingonthetrack

Accordingtoequation(13.9),wheelclimbingonarailrequiresthattheratioY/Qattainsthevalue1.3(vehicleonbogies).Asalreadyexplained(section13.7.2),noanalyticalexpressionofYasafunctionoftrackandrollingstockparametershasbeenformulated.Therefore,thewheelclimbingontherailisconsideredlikely,ifcertainrollingstockcharacteristicshavevaluesdifferentfromthosespecifiedduringpreventivemaintenance.Thisformofderailmentispredominantatlowspeeds,especiallyinthecaseofemptyrailvehicles.

Thecriticalvalueofangleβbetweenwheelandrailcanbedeterminedbycombiningequations(13.8)and(13.9).ConcerningtransverseforceQ,additionaldynamicloadsshouldalsobetakenintoaccountfromFigure8.15,fromwhichforV=120km/hthedynamicimpactfactoris1.2andthus:

Therefore,wewillhave

andderailmentsafetyfactorforthisangleisequalto1.

cDerailmentbyoverturningofthevehicle

Thisformofderailmentcanbestudiedinrelationtothegeometricalcharacteristicsoftherollingstock.Inanycase,thesafetyfactor,asdiscussedinsection13.7.3,hasinthiscasevaluesgreaterthan3.3,(259),(261).

13.8.Effectsoftransversewinds

Fortrackslaidinareaswithtransversewindsofhighintensity,theriskofoverturningoftherailvehicleshouldbecarefullyevaluated.Thisriskisgreater(by50%)formetricgaugetracks,(260).

LetusconsiderarailvehicleofamassMonacurveofaradiusRwithacanthforatrackwithagaugeG,(Fig.13.13).Inadditiontothetransverseforcespreviouslydiscussed,thevehicleissubmittedtoatransverseforceFw,duetoawindofamediumtransversespeedu,whichcausesanadditionaltransverseforceΔQbetweenthevehicleandtherail.

ThestaticanalysisofthephenomenonshowsthattheoverturningoftherailvehicleisarelationofthefactorΔQ/Qo,whichisfoundtobe,(259)

where:Qo:staticaxleload[=(M·g)/2],hg:heightofthecenterofgravityofthevehicle,hw:heightofthepointofapplicationoftransversewind,ρ:massoftheair,S:surfaceoftransversecross-sectionofthevehicle,c:aerodynamiccoefficientattheverticaldirection,V:trainspeed,u:transversewindspeed.

Fig.13.13.RailvehiclesubmittedtoatransversewindforceFw

Itwasfoundthattheoverturningofavehicleoccurswhen,(259)

Formulas13.13and13.14permit,inrelationtothetopographyoftrackandwinddata,theidentificationofareaswithahighriskofoverturningoftherailvehicle,duetotransversewinds,asfollows:areasofrestrictionofspeed.Thus,Frenchrailways,intheirhigh-speedParis-Marseilletrack(operatedatamaximumspeedof300km/h)limitthetrainspeedat170km/horat80km/hinrelationtothewindspeed(caseofwindswithaspeed100÷120km/h),(259),areaswiththehighestrisk,forwhichphysicalortechnicalfencesalongthetrackshouldbeinstalledforprotectionagainstwinds.

Aseriesofwindmeasures(speedanddirection)isnecessaryinordertoevaluateanycomingriskandtaketheappropriatemeasures.Thesedataareintroducedinsimulationmodelsandforecastsofwindspeed(anddirection)atanypointaretransmittedatleast5minutesbeforethepassingofatrainfromthatspecificpointwiththeappropriateinstructionforalimitation(ornot)ofspeed.

*Asexplainedinsection16.8,trackmaintenanceworksinvolverepeatedlyraisingthetrackorshiftingithorizontally,whichcausedestabilization.

1Aprocessistermedstochastic,ifitcanonlybeapproximatedbystatisticalmeasurements(e.g.earthquakes).Indeterministicprocesses,incontrast,correlationofcauseandeffectispossibleinadvance.Mostknownprocessesinrailways,inspiteoftheobservedspreadoftheresults,areconsideredasdeterministic(e.g.elasticity,etc.).

14TrackLayout

14.1.Railvehiclerunningonacurve

14.1.1.Effectsduringmovementofarailvehicleonacurve

Accordingtoelementaryphysics,avehiclerunningataspeedVonacurveofradiusRdevelopsacentrifugalaccelerationγ=V2/RandacentrifugalforceF=m·V2/R,withthefollowingadverseconsequences:reductioninpassengercomfort,importanttransverseforcesfavoringconditionsforderailment,increasedtransverseloadingofbothtrackandrollingstock,resultinginconsiderablewear,increasedvibrations.

Inordertoreducetheaboveunfavorableeffects,thefollowingmeasuresareavailable:•UsingaslargearadiusofcurvatureRaspossible.Suchameasureisnoteasilyimplemented,however,duetotopographicalconstraints,whichoftenmakelargeradiiconditionalonexpensivecivilengineeringprojects(bridges,tunnels,highembankmentsorcuts).

•Transversesuperelevation(alsocalledcant)oftheouterrailinrelationtotheinnerrail,tooffsetcentrifugalforces.Cantgreatlydecreasestransverseeffects,without,however,completelycounteractingtheminmostcases,sinceitcannotexceedcertainvaluesbeyondwhichrollingstockandtrackwearbecomeprohibitive.

•Reductionintrainspeed,whichconstitutesalastresortsolution,sincethetrendistoincreasetrainspeed.

14.1.2.Transitioncurve–Cubicparabolaorclothoid

Onastraightline,curvatureiszero,whileonacurveofradiusRcurvatureis1/R.Therefore,betweenastraightandacurvedtrack,thecurvaturechanges

abruptlyfromzeroto1/R.Passengersfeelthissuddenchangeofcurvatureasajolt.

Therefore,avariable-radiustransitioncurve,withzerocurvatureatthebeginningand1/Rcurvatureattheend,shouldbeinterposedforsmoothtransitionfromrectilineartocurvilinearmotion.

Asatransitioncurvebetweenastraightlineandacirculararc,acubicparabolaoraclothoid(asinhighwayengineering)maybeused.Inrailwayengineering,thecurvecommonlyusedbymanyrailwayauthoritiesisthecubicparabola.However,somerailways(amongthemBritishrailways)usetheclothoidasatransitioncurve.Curvatureρisdefinedas,(Fig.14.1):

Fig.14.1.Cubicparabola

Inthecubicparabola,curvatureρisproportionaltotheprojectionoftheparaboliccurveonthex-axis:

wherekisacoefficient.

InthecubicparabolaitmaybeassumedthatthelengthLofthetransitioncurvemaybeconsideredequaltoitsprojectionℓonthex-axis.Theapproximationintroducedbythisassumptionwasfoundsatisfactoryinmostcases.

Intheclothoid,curvatureρis

Usingthepreviousassumption,L=ℓ,itisfoundthatinmostcasestheuseofcubicparabolaandofclothoidgivesimilarresults.

Thecriticaldifferencebetweenaclothoidandacubicparabolaisthatwhereasaclothoidgoesroundandround,acubicparabolacanneverturnthroughmorethanarightangle,(Fig.14.2).

Fig.14.2.Comparisonbetweenclothoidandcubicparabola

14.2.Theoreticalandactualvaluesofcant–Permissiblevaluesoftransverseacceleration

14.2.1.Theoreticalvalueofcantforthecompletecompensationofcentrifugalforces

LetusconsiderarailvehiclerunningataspeedV(km/h)onacurvewitharadiusR(m).Weseekthevalueofthecantoftheouterrailinrelationtotheinnerrail,atwhichthecentrifugalforcesarefullycompensated.Wewilldesignatethisastheoreticalcanthth(mm).Thus,wehave:

FromFigure14.3wehave:

aswellas:

Fig.14.3.Forcesexertedonarailvehiclewhenrunningonacurveandtheoreticalcant

Fromequations(14.4)÷(14.8)andafterappropriateconversionofunits,itisderivedforstandardgaugetracksthat:

Inthecaseofmetricgaugetracks(withagaugeof1,000mm)itwillbe:

Inthecaseofbroadgaugetracks(withagaugeof1,524mm)itwillbe:

14.2.2.Appliedvalueofcant,cantdeficiencyandcantexcess

Equation(14.9)showsthatthetheoreticalvalueofcantforcompletecompensationofcentrifugalforcesisproportionaltothesquareofvehiclespeed.Assumingthatthelatterisconstantonacurve,asinglevaluehthoftheoreticalcantcanbecalculated.Thiscondition,however,isfulfilledonlyonmetropolitanrailwaysoronhigh-speedlinesusedonlybypassengertrains.Bycontrast,onconventionalrailwaylines,fast(passenger)andslow(freight)trainscoexist.

Thus,ifthemaximumspeedofpassengertrainsisusedinequation(14.9),thenpassengercomfortisensured.Withfreighttrains,however,problemsariseduetowearofboththewheelsandtrackequipment(specificallyoftheheadsoftheinnerrails).Furthermore,ifafreighttrainstopsonacurve,itwillhavetroublestarting(itwillevenbeunabletodosoiftheradiusofcurvatureistoosmall).

Ifinequation(14.9)theusualrunningspeedoffreighttrainsisapplied,thennoproblemsareencounteredinrelationtofreighttrains.Passengercomfort,however,isgreatlyimpaired,andtherearegreaterstressesontherailplacedhigher.

Acompromisebetweenthetwopreviousconditionsshouldthereforebefoundbyadoptingacantvalue,whichensurespassengercomfort,increasesonlymoderatelyrollingstockandtrackstresses,andallowstrainstostoponacurve.Thisintermediatevalueofcanthisoftentermedappliedornormalcant(orstandardcantbysomerailways).Wewillhave:

Selectingtheappliedvalueofcantresultsincantdeficiencyforfasttrainsandcantexcessforslowtrains.

Thedifferencebetweenthetheoreticalvalueofcantforthemaximumspeedandtheappliedvalueofcantistermedcantdeficiencyhd:

Thedifferencebetweentheappliedvalueofcantandthetheoreticalvalueofcantfortheminimumspeedistermedcantexcesshe:

Theappliedvalueofcant,asexplainedinsection14.4,willbecalculatedbytheequation:

14.2.3.Cantdeficiencyandtiltingtrains

Inordertodealwiththeproblemofnon-compensatedcentrifugalacceleration,certaintypesofrollingstocktiltautomaticallyonsmall-radiuscurves.

Theso-calledtiltingtrainstry(andoftenfullysucceed)toreducecant

deficiencyincurvesbytiltingthevehiclebodyinrelationtothewheel-base(Fig.14.4).Whenusingtiltingtrains,speedcanbeincreasedforsmall-radiuscurvesbyupto30%,comparedtoconventionalrollingstock.ThistechniquehasbeenappliedintheUK,Spain,Italy,Sweden,Japanandelsewhere(tiltingtechnologyisfurtheranalyzedinsection19.9).

Fig.14.4.Theadditionalsuperelevationgeneratedbytiltingtrains,(273)

14.2.4.Permissiblevaluesoftransverseacceleration

Insection7.12wehaveseenthatpassengercomfortdependsbothonthevalueofthetransverseaccelerationandonthedurationandfrequencywhicharefeltbythehumanbody.Thedirectioninwhichthetransverseaccelerationisexertedisalsocritical.Itisfoundthatanaccelerationof0.05gatafrequencyof1.5Hzcanbetoleratedfor5h30minintheverticaldirectionand3h30mininthehorizontaldirection,(147).

Considerationsofhumanphysiology,therefore,determinethemaximumvalueoftransverseaccelerationaswellasitsrateofchange.Thereisgeneralagreementthatmaximumtransverseaccelerationshouldneverexceedg/10,i.e.avalueof1m/sec2,(276).

Intracklayout,however,aconsiderablereductionofpassengercomfortcannotbetolerated.Consequently,thenon-compensatedcentrifugalaccelerationbshouldnotexceedapercentageofthemaximumtransverseaccelerationγacceptablebythehumanbody.Manyrailwayauthoritiessetthislimitasfollows,(279):

Inmetropolitanrailways,wherethedurationofthewholetripissmaller,ahighervalueofnon-compensatedcentrifugalaccelerationupto0.8m/sec2canbeconsideredacceptable.

Theselectedvalueofbaffectsthemaximumvalueofcantdeficiency.

14.2.5.Variationintimeofcantdeficiency

Thevariationofcantdeficiencyintimeis:

Theparameter maybeexpressedasafunctionofthevariationofcantdeficiencyperunitlength:

14.3.Limitvaluesofcant,cantdeficiency,cantexcessandnon-compensatedtransverseacceleration

14.3.1.LimitvaluesaccordingtoUIC

Aswillbeanalyzedinthenextsections,oncevaluesofcanthandnon-compensatedaccelerationbaredefined,thenforagivenvalueofspeedtheradiusofcurvatureRcanbecalculated(seeequation(14.36)below).

Limitvaluesofcantandnon-compensatedaccelerationareprescribedbyUIC,(276).Linesareclassifiedin4classes:

ClassI:Vmax:80÷120km/h,ClassII:Vmax:120÷200km/h,ClassIII:Vmax:250km/h,mixedtraffic.StandardsofGermanandSwiss

railwaysaregiven,ClassIV:Vmax:300km/h,onlypassengertraffic(caseoftheFrenchTGV).Foreachclass,applied,maximumandexceptionalvaluesofcant,cant

deficiency,cantexcessandnon-compensatedtransverseaccelerationaregiveninTable14.1,(276).Exceptionalvaluescanbeappliedonlyaftertherunningcharacteristicsoftherollingstockhavebeenverified.

14.3.2.LimitvaluesaccordingtoEuropeanspecifications

AccordingtotheEuropeantechnicalspecificationsforinteroperability,(134):a)Thelimitvalueofcantfornewhigh-speedtracksdedicatedonlytopassengertrafficissetto180mmandformixedtraffictracksto160mm,

b)cantdeficiencyforhigh-speedtracksshouldbecalculatedinrelationtothevalueofthenon-compensatedtransverseaccelerationb.Fortrackswithspeeds≤200km/h,thelimitvalueofcantdeficiencyissetto130mmforb=0.85m/sec2andto150mmforb=1.0m/sec2,

c)noreferenceismadeconcerningtrackexcess,d)therateofchangeofcantasafunctionoftimeissetto70mm/sec,whichundercertainconditioncanbeincreasedto85mm/sec,(134).

Table14.1.LimitvaluesofgeometricalcharacteristicsoflayoutaccordingtoUIC,(276)

14.3.3.Geometricalcharacteristicsoflayoutinsomehigh-speedtracks

Table14.2presentsthegeometricalcharacteristicsofthelayoutofsomehigh-speedtracksaswellasthoseoftheEuropeanspecificationsandthoseofUIC.

14.4.Calculationofthetransitioncurve

Insection14.2.2.wehaveexplainedthatthevalueofappliedcanthmustliebetweentwolimitstoensurethatnoproblemsarecausedtoeitherslow(freight)orfast(passenger)trains.AfterthelimitvaluesgiveninTables14.1,14.2,itshouldbe

andineachcase

Theselectionofavaluebetweenthetwolimitsofequation(14.19)dependsontherelativedensityofpassengerandfreighttrafficontheparticularline.Morepassengertrafficraisesthisvaluetowardstheupperlimitofequation(14.19),whilemorefreighttrafficmakesitapproachthelowerlimitofequation(14.19).

Table14.2.Geometricalcharacteristicsoflayoutofsometracks[compiledfromdataof

railwayauthorities]

Inallcases,however,theratioofthemaximumcanthmaxtothemaximumtheoreticalcanthmax+hdmaxshouldremainconstant.Thetheoreticalcantwillbemultipliedbythisconstantratiotofindtheappliedcant:

Theminimumvalueofcantshouldnotresultinanon-compensatedcentrifugalaccelerationgreaterthanbmax:

Thecantvaluesfoundfromtheforegoingequationsareroundedofftomultiplesof5mm.

Toensuresmoothtrainrunning,thevalueofcantshouldvarygraduallyfromzero(attheendofthestraighttrack)toh(atthebeginningofthecirculararc).Thisrequiresthatthesuperelevationrampandthetransitioncurvecoincide.

Fig.14.5.Transitioncurve(cubicparabola(OB))andcirculararc(BB’)

IfListhelengthofthetransitioncurveandℓitsprojectionontheextensionofthestraightsection,(Fig.14.5),thentheminimumvalueofthetransitioncurvecanbecalculatedbytheformula,(276):

Theordinatesofthetransitioncurve,whichisusuallyinrailwaysacubicparabola,arecalculatedbytheequation,(279):

Intheeventthattheterm ismuchlessthanℓ,itcanbeomittedin

equation(14.24),inwhichcasewehaveasmall-lengthcubicparabola.Itsequation,applicableaslongas is:

Theordinatesofthecubicparabolaarecommonlycalculatedevery10m,or,wheneveragreaterpointdensityisrequired,every5m.

ThelengthLofthecubicparabolaanditsprojectionℓonthestraightlinearerelatedbytheequation:

Certainrailwaysuseparabolictransitionsofahigherdegree(thirdorfourthdegreeparabolas).

Transitioncurvesarenotusedif:•thecalculatedvaluesofcantarepracticallyzero,•betweentwoadjacentcurves(ofthesamedirection),thevariationofaccelerationhasvaluesbetween0.2m/sec2and0.3m/sec2.

14.5.Calculationofthecirculararc

Letfbetheshiftproducedbythecubicparabolabetweenthestraightlineandthecirculararc,(Fig.14.5).Thecharacteristicsofthecirculararcarecalculatedbythefollowingequations,(142):

where isthesecantoftheangle (angleαexpressedingrades).

Theshiftfiscalculatedbytheequation

i.e.,inmostcasestheinfluenceoffonthelengthOKisnegligiblecomparedtoR.

14.6.Caseofconsecutivesamesenseandantisensecirculararcs

BetweentwoconsecutivecirculararcsofthesamesensewithradiiR1andR2,atransitioncurveisplacedadjacenttoeachcirculararcandanintermediaterectilinearsectionisinterposedbetweenthetransitioncurves.Formedium-speedtracks(Vmax=200km/h),thisrectilinearsectionhasausualvalueof30m.

Usingthefollowingsymbols:

thetransitioncurveadjacenttothecirculararcofradiusR1willbe:

ThetransitioncurveadjacenttothecirculararcofradiusR2willbe:

Iftheinterpositionofanintermediaterectilinearsectionisnotfeasible,then,insteadoftwotransitioncurves,asingletransitioncurvecanbeusedwiththefollowingequation:

or

whereL1,L2aretherequiredcurvelengthsfortransitionbetweentherectilinearsectionandthetwocirculararcs(withradiiR1andR2)andτistheanglebetweenthestraightlineandthetangentatthebeginningofthecirculararc,(Fig.14.5).

Betweentwoconsecutiveantisensecirculararcs,oneparabolictransitioncurveadjacenttoeachcirculararcandanintermediaterectilinearsectionatleast30mlong(preferablyV(km/h)/2)areinterposed.Shouldthelatternotprovefeasible,therectilinearpartisomittedandthetwotransitioncurveshaveacommonbeginningpoint,acommontangentandthesamecurvaturevariation,(Fig.14.8).

14.7.Superelevationramp

Asexplainedinsection14.4,thesuperelevationrampandthecubicparabolashouldcoincide.Inthiscase,thefollowingcantvariationdiagramresults,(Fig.14.6):

Fig.14.6.Diagramofvariationofcantandcurvaturebetweenrectilinearsectionandcirculararc

Asimilarlinearvariationofcantshouldbeappliedbetweensamesense,(Fig.14.7),orantisensecircularcurves,(Fig.14.8).

Fig.14.7.Diagramofvariationofcantandcurvaturebetweenconsecutivesamesensecirculararcs

Fig.14.8.Diagramofvariationofcantandcurvaturebetweenconsecutiveantisensecirculararcs

Themaximumgradientωofthesuperelevationrampshouldnotexceedthevalue144/Vmax,i.e.:

Superelevationrampsshouldnotbelocatedinareaswhereturnoutsorexpansiondevicesareplaced.Ifthisisnotpossible,speedrestrictionsshouldbeapplied.

14.8.Combiningmaximumandminimumspeeds

Equation(14.19),(section14.4),impliesthatwhenmaximumandminimumtrainspeedsonacurvediffersignificantly,itisdifficulttofindanappliedcantvaluewhichdoesnotcauseproblemstofreightorpassengertrains.Apassenger

trainspeedincreaseisaccordinglyaccompaniedbyafreighttrainspeedincrease,asshowninTable14.3.

Table14.3.Maximumandminimumspeedsonalayout

Forhighspeeds,thecoexistenceofpassengerandfreighttrainsismorecomplicated.Forthisreason,somerailwayshavespecializedtheirhigh-speedtracksonlyforpassengertraffic.

14.9.Relationshipoftrainspeedwithradiusofcurvature

WeshallnowcalculatethemaximumpermissiblespeedonacurveofradiusR,or,foragivenspeedV,theminimumrequiredradiusofcurvature.

Obviously,foragivenradiusR,thespeedVreachesamaximumwhenthemarginsforcanth,cantdeficiencyhdandcantexcessheareexhausted.

Fromequations(14.9),(14.15),(14.19),itfollowsthat:

Solvingequation(14.36)forVmaxweobtainthemaximumpermittedspeedforagivenradiusR,whereassolvingforRweobtaintheminimumrequiredradiusforagivenspeedVmax.

WithrespecttoRmin,however,itshouldbeensuredthatthemaximumcantexcessfortheminimumspeedVminofslowtrainscanbeapplied.Equation(14.36)gives:

whilesettingupthemaximumvaluesforhdmax,hemaxandsolvingforR,weobtaintheminimumradiusrequiredbyslowtrains(withVmin).

Withrespecttotheminimumspeed,therefore,equations(14.36)and(14.37)shouldbesimultaneouslyvalid,andthehighervaluefoundforRminwillbeused.

Table14.4.Percentageofcurveswitharadiussmallerthan500mforvariousEuropean

railways(metrosystemsarenottakenintoaccount),(278)

Wheneverpossible,railwaystrytoapplythemaximumpossiblevalueofR.Therearegreatdifferencesamongrailways,concerningpolicyonthelowervaluesofradius,principallyduetothemountainousorplanecharacteroftheground.Table14.4givesthepercentageoftrackscurvedat500morlessinsomeEuropeanrailways.

Whentheradiusofcurvatureofatrackissmall,trackgaugeisincreased,resultinginavaluehigherthaninstraighttracksections.Theincreaseisappliedtotheinnerrail.ForradiusR<400m,thetrackgaugecanbeincreasedupto1.455m(inthecaseoftimberandsteelsleepers)andupto1.440m(inthecaseofconcretesleepers),(seealsosections7.4and16.4.4).

14.10.Transitioncurvesinthecaseofvariationofthedistancebetweentheaxesoftwotracks

Thedistancebetweentheaxesoftwotrackscanchange(e.g.attheentranceandexitofstations)frombtoc,(Fig.14.9).Thetransitionbetweenbandcisrealizedwiththeuseoftwoantisensecirculararcswithoutanyintermediaterectilinearpart.Theradiusofcurvatureofeachcirculararciscalculatedbytheformula,(279):

ThetangentTofeachcirculararciscalculatedbytheequation:

andtheordinatesofthecirculararcarecalculatedbytheequation:

Fig.14.9.Acaseofvariationofdistanceofaxesoftwotracks

Fig.14.10.Consecutiveantisensecurvesfortransitioninthecaseofvariationofdistanceofaxesoftwotracks

14.11.Longitudinalgradientsandverticaltransitioncurves

14.11.1.Longitudinalgradients

Whereverpossible,thelongitudinalprofileofarailwaylinefollowsthegroundprofile.Longitudinalgradientsofrailwaysaremuchsmallercomparedtothoseofhighways.Themaximumvalueofthegradientmainlydependsonthecharacteristicsandpoweroftherollingstock.Theusualmaximumvaluesofgradientsonprincipallineswithmixedtrafficandspeedsupto200km/hrangebetween12‰÷15‰.ThemaximumgradientonthemainlinesofGermanrailwaysis12.5‰,butintheFrenchTGVPars–LyonsandtheGermanCologne–Rhein(bothwithonlypassengertraffic)itis35‰and40‰respectively,(seealsosection2.3.1,Table2.5andsection14.3,Table14.2).For

reasonsofadhesion,maximumgradientscanhardlyexceedthelimitvalueof40‰.Forinstance,somelightweightrailsystems,whichoperatevehicleswith50%oftheaxlesmotorized,havegradientsupto40‰,(141).Abovethis,theuseofarackrailwaymustbeconsidered.

14.11.2.Verticaltransitioncurves

ThetransitionbetweenlongitudinalsectionswithdifferentgradientvaluesismadebyinterposingacirculararcofradiusRv,whoseprincipalpurposeistolimittheverticalaccelerationexperiencedbypassengerstoacomfortablelevel.

Thetransitioncurveisnotnecessaryaslongasthedifferenceoftherespectivegradients(ifofthesamesense)ortheirsum(ifofoppositesense)islessthan2.5 ,i.e.providedthat:

TheverticalcurveradiusRviscalculatedforhigh-speedtracks(V>200km/h)bythefollowingformula,(271):

withαv:verticalaccelerationwhichhasarecommendedlimitvalueof0.22m/sec2andamaximumlimitvalueof0.44m/sec2.

However,forconventionaltracks(V<200km/h)theverticaltransitionradiusmaybecalculatedbytheapproximateformula:

whichinexceptionalcasesmaybereducedto

Table14.5givestheminimumverticaltransitionradiusasafunctionofspeedforconventionaltracks.

Table14.5.Verticaltransitionradiusasafunctionofspeedforconventionaltracks

ThetangentEoftheverticaltransitioncirculararciscalculatedbytheequation:

whereΔiisthegradientdifference,(Fig.14.11).Theordinatesoftheverticaltransitionarcarecalculatedbytheequation

Fig.14.11.Verticaltransition

Nochangesofgradientshouldbemadewheretherearetransitioncurvesatthehorizontallevelandhencesuperelevationrampsexist.Whereversimultaneousverticalandhorizontaltransitioncannotbeavoided,themaximum

radiusofcurvatureshouldbeused.Verticaltransitionsshouldterminateatleast5÷10mfromthebeginningor

theendofswitchesandcrossings.Verticaltransitionsshouldmoreoverbeavoidedonsteelbridgeswithoutballast.

AccordingtotheEuropeantechnicalspecificationsforinteroperability,(134):a)themaximumgradientforhigh-speedtracksdedicatedforonlypassengertrafficis35‰,

b)themaximumgradientforhigh-speedtrackswithmixedtrafficis12.5 ,butforsectionsupto3kmthemaximumgradientof20 ispermitted.

14.12.Someconsiderationsformetricgaugetracks

Previoustheoreticalanalysesfocusedonstandardgaugetracks,butarevalidforbroadandmetricgaugetracksaswell.Formetricgaugetracksthefollowingconsiderationsshouldalsobetakenintoaccount.

Theminimumradiusofahorizontalcurvatureonmainmetricgaugetracksshouldnotbelessthan100m.Verticalradiusofcurvatureforspeedsupto100km/hshouldbe2,000÷4,000m.Maximumcantshouldbe100÷110mmformetricgaugetracks,maximumcantdeficiency70÷90mm,andmaximumcantexcess45÷80mm,(140),(274).

14.13.Layoutdesignwiththeuseoftablesandcomputermethods

Tofacilitatelayoutdesign,mostoftheaforementionedequationsareusedintheformoftables.Suchtablessparethedesignertediouscalculationsandgivevaluesataglance.Almostallrailwayauthoritiesestablishedsuchtablesmanyyearsago(beforetheextensiveuseofcomputers).

However,developmentsincomputerhardwareandsoftwarehaverevolutionizedrailwaylayoutdesign.Severalsoftware*permittracklayoutcalculationanddesign,requiringonlythetopographyandthelimitvaluesofthelayoutparameters.Figure14.12illustratesthetracklayoutdesignofanewlineusingCAD(ComputerAidedDesign)software.Furthermore,withthehelpofcomputerapplications,morealternativeroutescanbeeasilysurveyedandthesolutionchosencanbestudiedingreaterdetail.Thus,itispossibletoeasilystudymanyalternativesolutions,comparethem,andchoosethebestsolution(i.e.theonewhichmaximizesstraightlinesandlowgradients,whileatthesame

timeminimizesearthworks,civilengineeringconstructionsandcosts).Layoutdesignmaybefurtherfacilitatedwiththeuseofsatellitesystems,

(270).

14.14.Constructionofanewrailwayline

14.14.1.Feasibilitystudy

Thedecisionforrealizingarailwaylineistheoutcomeofacomplexprocedureinwhichpoliticians,managers,economistsandengineersareinvolved.Feasibilitystudies,(seesection6.3),areapowerfultoolinrationalizing(economically)thechoiceofaspecificprojecttoberealizedafterahighlyselectiveprocedure.

Oncethedecisiontorealizeaspecificrailprojectismade,thenextstepistoconducttheenvironmentalandtechnicalstudies(preliminary,outlineandfinaldesign).

14.14.2.Preliminarydesign

Basedontheforecasteddemandcharacteristics,theappropriatetypesofrollingstockfortheprojectcanbedetermined.Eachrollingstocktypeischaracterizedbyitspower,maximumspeedandacceleration,maximumgradient,etc.

However,thetraveltimestakenintoaccountinthefeasibilitystudydeterminemediumandmaximumspeeds,whichinturnprescribethemaximumradius(forhorizontalandverticaltransition).

Fig.14.12.Tracklayoutdesignusingacomputeraideddesignmethod

Beforebeginningthepreliminarystudy,theengineermustcollectasmuchdataaspossible,whichshouldincludethefollowing,(277):–mappingatascaleof1/50,000or1/25,000,–anyavailableaerialphotography(ideallyfromsatellites),–landuseandtownplans,aswellasagriculturalplans,–anyavailablegeological,hydrological,meteorologicalandotherinformation,–anypreviousreportsonthestudyarea.

Atthispreliminarystage,allreasonablypossibleroutes(2÷4)shouldbestudied.Foreachroute,thehorizontalandlongitudinalsectionsarestudied.Theengineershouldlookforagoodverticalprofilewithasfewchangesupanddownaspossibleandforagoodhorizontalprofilewithasfewreversesofcurvatureaspossible.Basedonthese,majortechnicalprojects(bridges,tunnels),publicutilitiestobedisplacedandafirstestimationofcostareidentified.

14.14.3.Outlinedesign

Completionofthepreliminarydesignshouldresultindefiningaroutecorridorofinterest,whichmayvaryfrom50mwide,inreasonablyflatterrain,toperhaps2kmormoreinmountainousareas.

Theoutlinedesignisusuallypreparedatascaleof1/5,000,withcross-sectionssurveyedat100mintervals.Twoorthreealternativeroutesmaybe

studiedatthisstage.Duringthisphase,considerationsshouldcoverallaspectsincludingthe

following,(275):–futuretrafficandoperatingdemands,–axleloadandtrackgaugeparameters,–minimumradius,cant,andotherlayoutcharacteristics,–longitudinalgradients,–subgradeanddrainageaspects,–bridgesandtunnels,–constructionplanning.

Thesolutionchosenattheendofthisphaseisstudiedindetailinthefinaldesign.

14.14.4.Finaldesign

Thefinalstageofthestudyisgenerallycarriedoutatscalesof1/2,000or1/1,000indifficultterrainand1/1,000or1/500inurbanareas.Evenatthisstageofthestudy,itmaytakeseveralattemptstoattaintherightcompromisebetweenspeed,curvature,gradient,andsoilmechanicsconsiderations.

Engineersshouldalwayshaveinmindfuturemaintenancerequirements,whichtheyshouldtrytominimize.

14.14.5.Stakingofthetracklayout

Aftermakingthelayoutcalculationanddesign,theimplementationofthelayoutshouldbeprecededbystakingthetrack.Stakesaredrivenasfollows:ondoubletracks,intheaxisofthedoubletrack,bothonstraightandoncurvedsections,onsingletracks,onstraightsectionsregardlessofthesideofthetrack(rightorleft),andincurvedsectionsonthesideoftheouterrail.Stakingtheoutersideofthetrackoncurvesfacilitatesthepreciselayingof

theouterrailaccordingtothelayout.Thealignmentoftheouterrailiscrucial,becausetheouterrailguidesfastmovingtrains.Thespecificvalueofgaugeisgivenbythesuitablepositioningoftheinnerrail.

Doublestakingisusuallyavoidedondoubletracks,andstakesaredrivenintheaxisofdoubletracks.Inthiscase,theouterrailshouldbelaidwithgreatcareoncurvedsections,takingintoaccountthevalueofthetrackgaugeattheparticularpoint.

Ontransitioncurvesandcirculararcs,stakesaredrivenevery10m.Wheneveracloserstakingisnecessary,stakesaredrivenevery5m.Alongstraightsections,stakesaredrivenevery50m.

Attheoneendofaparabolictransition,whichcoincideswiththebeginningofastraighttrack,itshouldbeensuredthattheextensionofthestraightlineistangenttotheendoftheparabola.Thisiswhythestakingofaparabolictransitionisextendedby4stakes(spaced10m)alongthestraightsectiontoprovideatleasttwozero-deflectionpoints.Asurveyinginstrument,fromapointatleast200maway,shouldcheckthealignmentofthese4stakes.

Thespecificnumberofeachfixedpointandtherequiredcantaremarkedoneachstake.Thelayingofthetrackonthehorizontalplanefollowsstaking.Thisstageconsistsofplacingeachrailattheproperposition,onthebasisofthefixedpoints,atwhichthestakesweredriven,andthevaluesofthetrackgauge.

However,satellitesystemscangreatlyfacilitateamoreaccuratestackingofthetracktobeconstructedorrenewed,(270).

14.15.Environmentalaspectsoftracklayout

Environmentalconsiderationsshouldbecarefullytakenintoaccountrightatthebeginningofthepreliminarystageoftracklayout.Railwaymanagersandengineersshouldbeawarethatiftheenvironmentalconsiderationsarenotthoroughlytakenintoaccount,thereisahighriskofdesigningageometricallyperfectlayout,whichhoweverwillneverberealizedduetoenvironmentalrestrictions.

Ateamofspecialists,includingenvironmentalists,landscapearchitects,civilengineersandagriculturists,shouldstudytheenvironmentalaspectsoftheproposedproject.Thefollowingstepsarenecessaryforanenvironmentalapproachtothetracklayout,(272):–avoidingareasofnaturalbeautyinordertominimizeanyriskcomingfromenvironmentalreasons,

–tryingtominimizedisturbancesinneighboringareas,duetorailvibrations.Thebestwayistohavethemajorpartoflayoutincutsections.Inlayoutswhereembankmentsarenecessary,noisebarriersshouldbeinstalledinareasneighboringwithvillagesorcities,

–takingcareoftheareaswhererawmaterialcomingfromanexcavationaredeposited,inordertoreduceanycaseofpollution,

–preservingthevarietyofanimals,plantsandbirds.Asmanylayoutscutsome

areasandthusprohibitthecommunicationofanimalsfromtheonesidetotheother,specialtransversepassagesalongthelayoutshouldbeinstalledsothatfrogs,foxes,etc.,caneasilygofromtheonesideofthetracktotheother,

–adaptingtotheaestheticsoftheenvironment.Atthefinalstageofthelayout,thequantitiesofplantsandtreesthatwillbeplantedalongthetrackmustbecarefullycalculated,

–assuringstabilizationofsoils(bothincutsandembankments)bygivingtheappropriateslopeandbyplantingthebestsuitedplants,

–takingmeasuresandinstallingthenecessaryequipment,sothatallplantsandtreeswillhavetherequiredmoisture,

–installingasystemofmonitoring,sothatanevaluationoftheefficiencyofthemeasurestakencanbedoneeveryfiveyears.

*Amongthevarioussoftwarefortracklayout(horizontallevel,verticallevel,cross-sections)wementionMXRail,ODOS,INRail,etc.

15SwitchesandCrossings

15.1.Functionsofswitchesandcrossings

Afundamentalcharacteristicofrailwaysistheonedegreeoffreedomofthemovementoftherailvehicleonthetrack.However,trainsmusthavethepossibilitytochangecoursefromonetracktoanother.Thisisrealizedbyswitchesandcrossings*,definedastheequipmentandpartsthroughwhichthedirectionofmovementofarailvehiclecanbechangedwithoutinterruptingitscourse.

Switchesandcrossingstakeagreatvarietyofforms.Inspiteoftheirapparentcomplexity,theycanbedistinguishedintotwobasicforms,andathird,combiningthetwo: Simple,(Fig.15.1),ormultipleturnouts,allowingatracktobesplitintwo(sometimesthree)andthemovingrailvehicletochangecourse.Crossings,(Fig.15.2),wheretwotracksmeetatgradewithnochangeofcourse.Turnoutcrossings,combiningthefunctionsofturnoutsandcrossings(seebelowsection15.3,Figures15.10and15.11).

Fig.15.1.Turnout

Fig.15.2Crossing

Thus,thefunctionsofswitchesandcrossingsaretoenablerailroutestobranchfromortojoinupwithoneanother;toprovideflexibilitywithinaroutesothattrainsmaymovefromonetracktoanothertrack;andfinallytoenablevehiclestobesortedout.Inordertorespondefficientlytotheserequirements,switchesandcrossingsmustfulfillcertainrequirements,whichincludethefollowing,(288):–imposethefewestpossiblespeedrestrictions,–besitedexactlywhereoperationalexigenciesdemand,–providemaximumoperationalflexibility,–supporttheaxleloadrequiredtobecarried,–becheaptomanufacture,simpletolay,easilyworked,robust,andeasytoreplace,

–resistwear,corrosionanddecay,andrequireminimummaintenance,–becompatiblewithsignalingrequirements.

15.2.Componentsofaturnout

Inaturnoutwedistinguish,(Fig.15.3):–themaintrackandtheturnout(ordiverging)track,towhichthevehiclecanbediverted,–themathematical(orintersection)point0oftheturnout,whichisthepointwheretheaxesofthetwotracksintersect,

Fig.15.3.Componentsofaturnout

–thefrogangle,definedbytheaxesofthetwotracks.Thefrogangleiscommonlydenotedbyitstangent(e.g.1:9).Thefrogangleconsistsofhigh-gradematerial(usuallymanganesesteel),–thestockrail,whichistherailthatstaysmotionless,

–theswitchortonguerail,whichisthemovingrailwhichchangesthecourseofthevehicle.AcriticalparameteristheradiusofcurvatureRoftheswitch.Dependingontheirposition,switchrailsallowrailvehiclestoproceedtooneortheothertrack,–thecheckrail,whichisarail(3÷10mlong)placedexactlyoppositethefrog.Shortlybeforethefrog,awheelreachesarailgapanditisnecessarytoprovidetheotherwheelwithaguidebarpreventingirregularanduncontrolledmovement,whichisachievedbyinstallingacheckrail.Thegapbetweenstockrailandcheckrailis38÷46mm,–thedistancesL1(fromthebeginningoftheturnouttothemathematicalpoint)andL2(fromthemathematicalpointtotheendoftheturnout),–theturnoutlengthL(L=L1+L2),

–thefoulingdistancec,whichisthedistancefromthebeginningoftheturnouttothepointbeyondwhichavehiclemaylieononetrackoftheturnoutwithoutinterferingwiththemovementofanothervehicleontheothertrack.Thispointisspecifiedsothatthedistancebetweentheaxesofthetwotracksisatleast3.50mforstandardgaugetracksand3.00mformetricgauge

tracks.ValuesoftheswitchradiusRforconventionaltracksusuallyrangebetween

150÷500m,permittingspeedsatthedivergingtrackof35÷65km/h.Forlowandmediumspeedtracks,thefrogangle(tangentoftheangleω)inoldturnoutswasgivenvaluesof1:8and1:10,whileinmorerecentlyinstalledturnoutsittakesusuallyvaluesof1:9or1:12.

Thecross-sectionoftheswitchrailtakesformgradually,asshowninFigure15.4.

Fig.15.4.Changingcross-sectionoftheswitchrailwithincreasingdistancefromthetoeoftheswitch

15.3.Variousformsofturnouts

Turnoutsandcrossingstakeagreatvarietyofformsdependingontheintendedchangeofcourse.Thefollowingaretheprincipalones.

•Standardturnout,inwhichonetrackissplitintwoandthemaintrackremainsrectilinear,(Fig.15.5).

Fig.15.5.Standardturnout

•Simplesymmetricalturnout,withonetracksplitintwoandbothtrackscurvingoutward,(Fig.15.6).

Fig.15.6.Simplesymmetricalturnout

•One-sideddoubleturnout,withonetracksuccessivelysplitintothreetracksonthesamesideandwiththemaintrackremainingrectilinear,(Fig.15.7)

Fig.15.7.One-sideddoubleturnout

•Two-sideddoubleturnout,withonetracksymmetricallysplitintothreetracks:amiddlerectilineartrackandtwosymmetricalsidetracks,(Fig.15.8).

Fig.15.8.Two-sideddoubleturnout

•Diamondcrossing,wheretwotracksmeetwithnochangeofcourse,(Fig.15.9).

Fig.15.9.Diamondcrossing

•Singleslip,wheretwotracksmeetandtheircoursecanonlybechangedfromonetracktotheotherinonedirection,(Fig.15.10).

Fig.15.10.Singleslip

•Doubleslip,wheretwotracksmeetandtheircoursecanbechangedfromonetracktotheotherinbothdirections,(Fig.15.11).

Fig.15.11.Doubleslip

•Singlecrossoverbetweentwoparalleltracks(1)and(2).Coursecanbechangedfrom(1)to(2)inthedirectionA(orfrom(2)to(1)inthedirectionB)butnotfrom(2)to(1)inthedirectionA,(Fig.15.12).

Fig.15.12.Singlecrossoverbetweentwoparalleltracks

•Doublecrossover(sometimescalled‘scissors’)betweentwoparalleltracks(1)and(2).Coursecanbechangedbothfrom(1)to(2)andfrom(2)to(1),(Fig.15.13).

Fig.15.13.Doublecrossoverbetweentwoparalleltracks

•Seriesofsuccessiveturnouts,whereonetrackissuccessivelysplitintoseveraltracks,(Fig.15.14).

Fig.15.14.Seriesofsuccessiveturnouts

•Track‘fan’withsuccessivetracksplittings,atechniqueusedindepotsandmarshallingyards,(Fig.15.15).

Fig.15.15.Track‘fan’

15.4.Runningspeedonturnouts

Turnoutsdifferfromregulartrackinthatneithercantnortransitioncurvesareused.Therefore,themaximumrunningspeedonaturnoutdependsonthevalueofthenon-compensatedcentrifugalaccelerationbandtheradiusofcurvatureRoftheturnout.

Theminimumvalueofcantinrelationtothenon-compensatedcentrifugalaccelerationis(seesection14.4,equation(14.22)):

Thenon-compensatedcentrifugalaccelerationbatturnoutsmustnotbetoohighforreasonsofcomfortandwear.Limitvaluesofbmaxusuallyrangebetween

0.6÷0.7m/sec2.Astheturnout’scantiszero,hmin=0,fromformula(15.1)weobtain:

Somerailwayscalculaterunningspeedontheturnoutinrelationtocantdeficiencyhd.Inthiscase,insteadofformula(15.2)thefollowingformulacanbeused:

Thus,theminimumradiusofcurvatureoftheturnoutwillbecalculatedwhenconsideringthelimitvalueofthenon-compensatedcentrifugalaccelerationbmaxorofcantdeficiencyhd.Formanyrailwaysbmax=0.7m/sec2,andbysubstitutingthisvalueintheformula(15.2),weconcludethattherelationshipbetweentherunningspeedontheturnoutandtheradiusoftheturnoutis:

Turnoutsaredesignedascubicparabolasofsmalllength,(seesection14.4,equation(14.25)),inaccordancewiththeequation:

Fromequation(15.4)itisdeducedthatinordertohaveatthedivergingtrackatrainspeedofV=120km/h,theturnoutradiusofcurvatureshouldbeatleastR=1,600m,whileforaspeedofV=150km/haradiusR=2,500misrequired.

Suchalayout,however,wouldclearlybeexcessivelyextravagantinspacerequirements.Furthermoreitassumestheabilitytodesignaswitchinwhichthetonguerailcanbebroughttrulytangentialtothestockrail.Forthesereasons,inpracticalturnoutdesigntheswitchismademuchshorterthanprevioustheoreticalconsiderationswoulddemand.Thisisrealizedbycuttingthestockrailatafiniteangle,knownastheswitchentryangle,(288).

Themaincharacteristicsofaturnoutusuallyincludeitsradiusofcurvature,thefrogangle(tangentoftheangleω,seeFig.15.3),andthetonguerail.

15.5.Geometricalcharacteristicsofturnouts

Therailwayindustryoffersagreatvarietyofturnouts.andconstructorscanoftenadjustthemtoconditionsinsitu.Table15.1givesapanoramaofsomerepresentativeturnoutsinuseforstandardgaugeandmetricgaugetracks.

However,minordifferencesingeometricalcharacteristicsmaybeobservedfromoneconstructortoanother.

Table15.2givesgeometricalcharacteristicsofsomerepresentativeformsofcrossingsforstandardgaugeandmetricgaugetracks,(282),(286).

Table15.1.Geometricalcharacteristicsofsomerepresentativeformsofturnouts,(282),

(286)

Table15.2.Geometricalcharacteristicsofsomerepresentativeformsofcrossings,(282),

(286)

15.6.Derailmentcriterionforswitchesandcrossings

Fig.15.16.Wheel-railcontactataturnout

Onaturnoutoracrossing,awheelflangemayclimbarailandcausederailment.Topreventthisevent,theratioY/Q(whereYisthetransverseforcebetweenwheelandrailandQisthewheelload)shouldnotexceedavaluegivenbyequation(13.8)ofsection13.7.2(Nadal’sformula,knownalsoafterthenamesofBoedecherandChartet,whopresentedthesameformulaatthesametime

withNadal):where:β:therail-wheel(flange)angle,

f:therail-wheelcoefficientoffriction.

StartingatthelowestY/Qvaluefoundfromempiricaldataandthemeanvalueoff,avaluepreventingderailmentcanbecalculatedfortheangleβandthereforethemaximumpermissiblewearoftheinnersurfaceofthewheelflangecanalsobecalculated.

Inordertopreventderailmentonaturnout,itissuggested,(284),(287),inlightofthestudyofmanycasesofderailmentsonturnouts,thatthenecessaryconditionforderailmentis:

Giventhelayingandmaintenancecriteriaforturnouts,itismoreadvisabletotakeintoaccountforthecriticalconditionofY/Qavalueontheorderof0.8,whichismoretypicalofactualconditionsofsafetyandderailment,(281),(288).

Therefore,forawheelloadof20tn,anaveragevaluef=0.3,andconsideringthecriticalvalueY/Q=0.8,itcanbecalculatedfromformula(15.6)that

15.7.Turnoutsonacurvedmaintrack

Untilnowithasbeenassumedthatthemaintrackisstraight.However,ifthemaintrackiscurved,thespeedatwhichaturnoutcanbeconvenientlyrunwillbechangedandtherelevantanalysisisgivenbelow.Let:Ro:radiusofstandardturnoutoutofstraightmaintrack,

Rm:maintrackradiusofcurvedturnout,Rt:desiredradiusofturnoutofmaintrackcurvedatRm.Aturnoutonacurvedmaintrackcanbeincontraryorsimilarflexure.For

contraryflexure,curvatureofcurveRtwillbe:

whereasforsimilarflexureitwillbe:

15.8.Turnoutsrunwithincreasedspeeds

Inturnoutsrunwithincreasedspeeds,thefrogangleisreduced.Thusthe

Germanrailwaysuseaturnoutwithafrogangleof1:42,inwhichthedivergingtrackcanberunataspeedof200km/h(lateralaccelerationbeing0.5m/sec2inthiscase).

Table15.3givesthegeometricalcharacteristicsofturnoutsthatcanberunwithincreasedspeeds,accordingtothespecificationsofUIC,(281).ItistonotethatinthetwolastcasesofTable15.3(R=3,000mandR=6,720m)forwhichtheradiusofcurvaturechangesfromvalueR(3,000mor6,720m)toR’(∞),thefrog(intersection)anglealsochangesfrom1:43.65to1:46(caseofradiusR=3,000m)andfrom1:61.68to1:65(caseofradiusR=6,720m).

Forthevariousturnoutswhichcanberunwithincreasedspeeds(Table15.3),Table15.4illustratesthevaluesofrunningspeedontheturnoutinrelationtotheradiusofcurvatureandthecantdeficiencyorthenon-compensatedcentrifugalaccelerationb,(281).

Table15.3.Geometricalcharacteristicsofturnoutsthatcanberunwithincreased

speeds,(281)

Table15.4.Maximumrunningspeed(km/h)onturnoutsrunwithincreasedspeeds,inrelationtotheradiusofcurvature,cantdeficiencyandnon-compensated

acceleration,(284)

15.9.Sleeperandtracklayoutinturnoutsandcrossings

Inthecaseoftrackontwin-blocksleepers,timbersleepersareusedintheturnoutarea.Ifthetrackislaidonothersleepertypes(monoblock,timber,steel),thenthesamesleepertypeisusedforboththeturnoutareaandtheremainderofthetrack.

Sleepersarelaidperpendiculartotheaxisofthemaintrackuptotheedgeofthecheckrail,(Fig.15.17).Beyondthispoint,theyarelaidperpendiculartothebisectrixoftheturnout.

Figure15.17illustratesthetrackandsleeperlayoutforaturnouttypeUIC60,whileFigure15.18illustratesaturnoutaccordingtotheAmericanspecification.

Fig.15.17.TrackandsleeperlayoutinthecaseofaturnouttypeUIC60

15.10.Manualandautomaticoperationofturnouts

Aturnoutmaybeoperatedeithermanually(bylocalorremotelevers),(Fig.15.19)orautomatically,(Fig.15.20).Automaticoperationisdrivenbyelectricactivatorsoperatingoncommandsfromelectriccontrolboards,operatedbystationpersonnelinchargeoftrainoperation,(285).

Aturnoutoperatesasfollows:Oneofthetwoswitchrails,(seeFig.15.3),staystangenttotherailadjacenttoit,whiletheotherswitchrailleavesfromitsneighboringrailagapsufficientforpassageofthewheelflange,(Figures15.3,15.21).Whenthesetofthetwoswitchrailsisoperated,eithermanuallyorautomatically,theabovestatesareinterchangedandtheswitchrailincontactopens,whiletheotheroneclosesthegap.

Inautomaticswitchoperation,thefollowingcontrolsareperformedautomatically,(Fig.15.21):–managementofthedistancebetweenthestockandswitchrail,–examinationofcheckrailgaugeandwearinthefrogarea.

Fig.15.18.TrackandsleeperlayoutinthecaseofanAmericanturnoutaccordingtotheAmerican(AREA)specification

Fig.15.19.Manualoperationofaturnout

Fig.15.20Automaticoperationofaturnout

Fig.15.21.Automaticswitchoperation

15.11.Designprinciplesforswitchesandcrossings

Inadditiontopreviousanalyticalmethodsandformulas,someempiricalconsiderationsshouldalsobetakenintoaccountwhendesigningswitchesandcrossings,(280),(282): thetensilestrengthoftherails,switchrailsandcheckrailsusedintheswitchesshouldbeatleast8,800kg/cm2.Allsurfacesmusthave

anindustrialfinishinaspecialheat-treatmentprocess,whichincreasestensilestrengthto13,000kg/cm2, switchesaremanufacturedintheformofspringswitchbladesorflexibletongues.Therunningedgesofthedivergingtrackareintheformofacirculararc.Elasticstockrailbracingisusedinsideinordertofastenthestockrails, thecheckrail,whichismadeofspecialsectionalsteel,isfastenedtosupportplatesandistherebyconnectedtotherunningrail.Toaccountforcheckrailwear,spacerscanbeinsertedtocorrecttheswitchopeningandthespacebetweenrailfaces.

Switchesandcrossingsshouldnotbelocatedinthefollowingareas:

–intunnelsandbridges,–onsharphorizontalcircularcurves,–onhorizontaltransitioncurves,–incasesofhighcant.

However,accordingtotheEuropeantechnicalspecificationsforinteroperability,(134):•therailinswitchesandcrossingscanbedesignedtobeeitherverticalorinclined,•allmovablepartsofswitchesandcrossingsshouldbeequipped(forbothnewandupgradedhigh-speedtracks)withameansoflocking.

Switchesandcrossingsshouldbeinspectedinregularintervalsinordertocheckforcorrectnessofthecheckandwingrailflangeways,thatallboltsscrewsandfasteningsarefitted,andthatthereisnoneedforthemaintenanceofweldings.

*Althoughswitchesaresometimesreferredtoasturnouts,theformer,strictlyspeaking,donotincludethefrogsandcheckrails(seebelowsection15.2andFigure15.3)enablingonerailtocrosstheother,whilethelatterdo.

16LayingandMaintenanceofTrack

16.1.Layingoftrack

16.1.1.Mechanicalequipment

Thelayingoftrackiscarriedout,nowadays,withtheuseofdifferentkindsofmechanicalequipment.

Beforelayingthetrack,itshouldbeverifiedthatthesubgradehasbeenproperlycompacted(seechapter9)andthatthetransverseslope(3÷5%)iscorrectlygiven.

Ballastistransportedwithspecialwagonsandisplacedinsitu.Theballastbedshouldbeproperlyleveled,gradedandconsolidated.Agantryoralight-typevehicleisusedtopullascarifierfortheusualscarifyingofthetopballast,togradethetopballastwithasmallgradingmachine,andalsotoconsolidatetheballastbedwithavibratingplateorrollervibrator.

Layingofrailsandsleepersisdonewiththeuseofmoresophisticatedmachines.Railsarelaidcontinuouswelded,somethingthatrequirescarefulcontroloftheweldingprocedures.Anotheressentialfeatureofrailsiscleanliness,thatis,freedomfromoxideinclusionsandminimalhydrogenlevels,(299).

Sleepersshouldbecorrectlyanduniformlyspaced.Theuniformityofsleeperspacingisjustasimportantasthenominalspacing.

Padsandfasteningsshouldbeproperlyadjustedonthesleepers.Theidealfasteningdoesnotrequiremaintenance,butifitdoes,thenitshouldbeeasyandatthelowestpossiblecost.

Therearemanytypesoftracklayingmachines.Thusahigh-speedlayingmachine(withaworkshiftof6hours)canachieveanaverageoutputof1.3kmpershift.Peakoutputscanreach500m/hand1.5÷2.0kmpershift,(289).

Fig.16.1.Railpositioningmachine

Oncethetrackislaid,railsarepositionedwiththehelpofarailpositioningmachine,(Fig.16.1).

Similarmechanicalequipmentandmethodsareusedbothforrenewingoldtracksandforlayingnewonesonvirginterritory.However,additionalmechanicalequipmentisneededfortheremovaloftheoldtrack.

Itshouldbeemphasizedthatfullymechanizedtrackrenewalandlayingmethodswouldhavetobeadaptedtotheparticularconditionsofeachrailwayauthority(railwaynetworkorinfrastructuremanager).

However,developingcountrieswithlimitedfundsmaynotfinditpossibletoinvestinallthesophisticatedmaterialofafullymechanicallayingprocess.In

suchcases,thereisequipmentavailablewhichenablescountrieswithasurplusoflow-costlabortoinstallmoderntrackassembliesandsomeofthesmalleritemsofthephysicalplanttogetherwithhandtoolssuchas:sleeperandrailhandlingtools,manualrailchangers,railskaterollerequipment,railscooters,smallhydraulicfasteninginstallationequipment,handballasttampingmachines,railsaw,raildrills,jacks,slewingbars,etc,(303).

16.1.2.Sequenceofconstructionofthevarioustrackworks

Inordertosavebothlaborandtimeandachievethebestuseoftheavailablemechanicalequipment,thevarioustrackworksmustbewellscheduled.Optimalschedulingcan,nowadays,bedonewiththeuseofspecializedsoftware,suchasPrimavera,MicrosoftProject,etc.

Intheschedulingoftracklayingworks,thefailureofjustoneoperation,atonelocation,ononeday,willdisruptthewholesequence.Suchdisruptionsshouldbeasfewaspossibleandwhereadisruptionisexpected,thesequenceofworksshouldbedulyreformulated.

16.2.Trackmaintenanceandparametersinfluencingit

Inpreviouschapterswehaveexaminedmethodsforoptimizingthedesignandconstructionofthetrack.However,afterthevariousrailwaysystemcomponentsstartoperating,degradationbeginsand,afteracertaintime,maintenancebecomesnecessary.Trackmaintenanceaffectsdecisivelybothtrainsafetyandpassengercomfort.Trackmaintenanceexpensesrepresentasignificantpercentageoftotalrailwayinfrastructureexpenses.

Therefore,trackmaintenanceexpensesshouldbekeptaslowaspossiblewhileensuring,foraspecifictrainspeed,thatsafetyandpassengercomfortremainatanacceptableandsatisfactorylevel.Withrespecttosafety,maintenanceshouldbepreventive;regardingcomfort,maintenanceshouldbecorrective;andasregardstheeconomicaspectsofmaintenance,anoptimumsolutionshouldbesought,soastoensureasatisfactorysafetymarginandpreventaquickdegradationoftrackquality.

Theaboveobjectivesdependontwofundamentallydifferentclassesofparameters:ontheonehand,geometricalparameters,thedegradationofwhichisusuallyreversible;andontheotherhand,mechanicalparameterswhichinmostcasescannotberestoredwithoutpartsreplacement(rails,fastenings,sleepers,welds,etc.).

Geometricalparameters,however,evolvemuchfaster,about5÷15times,thanmechanicalparameters,(304).Accordingly,inlineswithanaveragetrafficload(20,000÷40,000tons/day,UICgroup4),whicharerepresentativeofthemajorityoflinesallovertheworld,systematicrestorationofgeometricalcharacteristicsisdoneafteratrafficloadofabout40÷50milliontons,whilerailsarereplacedafterabout500÷600milliontons.Thismeansaboutfouryearsbetweenscheduledmaintenancesessionsandrailandconcretesleeperreplacementevery40÷50years(theabovefiguresareindicativeoftheorderofmagnitudeonly).

Deviationsbetweentheactualandtheoreticalvaluesofgeometricaltrackcharacteristicsaretermedtrackdefectsandtheirrestorationisaccomplishedthroughtrackmaintenance.Trackdefectsshouldbedistinguishedfromraildefects(seesection10.9.1).

16.3.Definitionsandparametersassociatedwithtrackdefects

Letzi(T,x)andzo(T,x)betheelevationoftheinnerandtheouterrail,respectively,correspondingtoatrafficloadT(sincethelasttrackmaintenance),atakilometricpositionx.Wedefinethefollowingparameters,(Fig.16.2):Trackelevationz(T,x)

Tracksettlemente(T,x)e(T,x)=z(0,x)–z(T,x)

Fig.16.2.Definitionofbasicparametersfortrackmaintenance

Meansettlementme(T)overatracklengthL

Formeasurementsperformedatdiscretepositionsandnotcontinuously,itwillbe:

DifferentialsettlementΔe(T,x)Δe(T,x)=e(T,x)–me(T)

Standarddeviationofthesettlement,sde(T),overatracklengthL

andfordiscretevalues

Theoreticalelevationofthetrackzth(T,x)Therealpositionz(T,x)ofthetrackoscillatesaroundatheoreticalposition,

which,beingunknown,isapproximatedoveracertainlength2λaroundpositionx,bythevaluezth(T,x)givenbytheequation:

16.4.Trackdefects

16.4.1.Longitudinaldefect

ThelongitudinaldefectLD,(Fig.16.3.a),isdefinedasthedifferencebetweenthetheoreticalandtherealvalueoftrackelevationandisgivenbytheequation

Thelongitudinaldefectisthemostreliableinillustratingtheeffectoftheverticalloadsontrackqualityandistheprincipalfactor(togetherwiththetransversedefect,seebelow,whichaccompaniesthelongitudinaldefect)indeterminingthemagnitudeofthetrackmaintenanceexpenses.

Fig.16.3.Longitudinal,transverseandhorizontaltrackdefects

16.4.2.Transversedefect

ThetransversedefectTD,(Fig.16.3.b),isdefinedasthedifferencebetweenthetheoreticalandtherealvalueofcant:

where:zi:elevationofinnerrail,zo:elevationofouterrail

Forrectilinearpartsofthelayout,wherecurvatureiszero,thetransversedefectisthedifferenceofelevationbetweeninnerandouterrail:zi–zo.

16.4.3.Horizontaldefect

Thehorizontal(oralignmentorlateralalignment)defectHD,(Fig.16.3.c),isdefinedasthehorizontaldeviationoftherealpositionofthetrackfromitstheoreticalposition.Thehorizontaldefectdependsonthetransversetrackeffects(morethanthetwoprevioustypesofdefects)andonthecharacteristicsandparticularitiesoftherollingstock.

16.4.4.Trackgauge

Deviationsofrealvaluesoftrackgaugefromnominalvaluesareaffectedbythemechanicalpropertiesoftrackmaterials,theparticularitiesoftherollingstock,andthetrainspeed,asgiveninTables16.2and16.5.

16.4.5.Tracktwist

Alongstraightandcircularsections(wherecantisconstant),fourpointsofthetracklyingontwotransversesections(e.g.ontwosleepers,asshowninFigure16.4)mustlieinthesameplane.Tracktwistisdefinedasthedeviationofonepointfromtheplanedefinedbytheotherthree.

Fig.16.4.Tracktwist:thedeviationofonepointfromtheplanedefined

Ifiandi+1aretwosuccessivetransversesectionsofthetrack,spacedΔℓapart,(e.g.,atthepositionsoftwosleepers),tracktwistisdefinedasthevariationofthetransversedefectperunitlength,

Theriskofderailmentisreducedwhentherealvalueoftwistissmallerthanitscriticalvaluecausingderailment,whichdependsmainlyonspeedandtoalesserdegreeonthetypeofthetrackequipmentandoftherollingstock.

Itcanthereforebeconcludedthatthetracktwistandthetransversedefectarenotindependentparameters.However,theyareoftenexaminedseparatelybecausetracktwistisoneofthemostfrequentcausesofderailment,especiallyforspeedsV<140km/h.Themaincriticalsafetyparameteratthesespeedsistracktwist,whileothertrackdefectspreviouslymentionedareoflesserimportance,(301),(305).

16.5.Recordingmethodsoftrackdefects

Competentmaintenancepersonneldetectedtrackdefectsuntilsomedecadesagoeithervisually(thismethod,permittingthedetectionofonlylargedefects,didnotproverationalnorfreeofsubjectiveassessment)orbysimpleinstruments.However,inrecentyears,modernrailwaytechnologyhasbeenusingrecordingvehicles,(Fig.16.5),travelingthetrackatspecifiedintervals(formainroutes:3times/year,forintermediateroutes:2times/year,forbranchlines:once/year).Thesevehiclesareprovidedwithrecordingequipmentwhichmeasuresthevaluesofthevarioustrackdefectsinaccordancewithaspecificbasisof

measurement(intheorderof10mforlongitudinal,transverseandhorizontaldefectsandintheorderof2.5÷3mfortracktwist).Asthereexistmanytypesofrecordingvehicles,whenevervaluesoftrackdefectsaregiven,theyshouldbeaccompaniedwithvaluesofthemeasurementbasis.ArecordingvehicleillustratedinFigure16.5correspondstothechordoffsettype.Therealsoexiststheinertialmeasuring-typerecordingvehiclebasedontechnologiessimilartothoseusedtomeasurehighwayandairportrunwayirregularities.Figure16.6illustratesarecordingoflongitudinaldefects.

Thedistributionofthevarioustypesofdefectsisofastochasticnatureandcanbeapproximatedwiththeaidofspectralanalysis.Thus,foreachclassofdefects,thefollowingcanbecalculated:theirfrequencyofoccurrence,thewavelengthtowhichtheycorrespond,theirrelationtotrainspeed,etc.

Fig.16.5.TrackdefectrecordingvehicleofFrenchrailways

Fig.16.6.Longitudinaldefectsasrecordedbytherecordingvehicle

Thesimplestapproachistocalculatethemean(unsigned)valuesofadefectaswellasitsmaximumvaluesoveraparticularlength.Boththeformerandthelatterwillbedesignatedasabsolutevaluesofdefects.Theyareusedatlowandmediumspeeds,wherethesearethecriticalanddeterminingparameterson

whichsafetydepends.However,formedium-,rapid-andhigh-speedtracks,thedecisiveparameters

arethosedeterminingpassengercomfort.Atthesespeeds,ensuringahighlevelofpassengercomfortalsoensurestrafficsafety.Consequently,asindicesoftrackqualityattheabovespeeds,theprocessedvaluesofthevarioustypesofdefectsareused(obtainedfromthevaluesrecordedbytherecordingvehicle).Mostcharacteristicoftheseprocessedvaluesisthestandarddeviationofaparticulartypeofdefectoveraspecifiedlength(usually200÷300m),whichreliablysimulatesvariationsinthevaluesofthedefectinquestion,(300),(304).

Itshouldbenotedthatonmedium-speedtracksboththeabsoluteandtheprocessedvaluesareusedasindices,theformermoreoften.

Recordingvehiclesareequipped,nowadays,withcomputersoftwarewhich,inadditiontotheresultsofrecording,canprovidethefollowing:rankingofdataaccordingtoseverity,comparisonwithresultsofpreviousrecordings,comparisonwithlimitvalues(seebelow,section16.6)specifiedbystandards,etc.

Itwillbeveryusefulifrailwayindustrycanprovideinthecomingyearsrecordingvehicleswiththecapacitytoalsomeasurerailcharacteristics,suchascorrugationseverity,railheaddamage,sidewear,etc.

16.6.Limitvaluesoftrackdefects

16.6.1.Limitvaluesforhigh-,rapid-andmedium-speedtracks

Foreachspeed,twolimitvaluesarespecified,(295),(296):•alertvaluesoftrackdefects,which,whenreached,requireschedulingtheinterventionoftrackmaintenanceteams.ThesevalueswillbedesignatedasLinf,

•uppervaluesoftrackdefectsforimmediateaction,whichshouldnotbereached,otherwisethedeteriorationintrackqualitymaybecomeirreversible.UppervalueswillbedesignatedasLsup.

ThedecisiontorealizemaintenanceworksshouldbetakenbetweenthelimitsLinfandLsup.

Tracksareusuallyclassifiedinfourcategories,dependingontrainspeed,asfollows,(297):

I.high-speedtracks(V>200km/h),

II.rapid-speedtracks(140km/h<V<200km/h),III.medium-speedtracks(100km/h<V<140km/h),IV.low-speedtracks(V<100km/h).AccordingtotheFrenchrailways,thestandarddeviationforlongitudinal,

transverseandhorizontaldefectsandfortrackcategoriesI,II,IIIisgiveninTable16.1.

Table16.1.Standarddeviation(mm)oflongitudinal,transverseandhorizontaldefects

foralengthof300mforvariouscategoriesoftracks,accordingtotheFrenchrailways,(304)

16.6.2.Limitvaluesformedium-andlow-speedtracks

Asdiscussedinsection16.5,decisionsabouttrackmaintenanceformedium-andlow-speedtracksaretakeninrelationtothemaximumvaluesofdefectsasrecordedbytherecordingvehicle.Wedistinguishtwolimits:–interventionlimits,whicharevaluesoftrackdefectsthatnecessitate,whenreached,interventionandtrackmaintenance,

–acceptancevalues,whicharevaluesoftrackdefectsthatcanbeleftaftertheexecutionoftrackmaintenance,sinceitispracticallyimpossible(andverycostly)toattainageometricallyperfecttrack.Table16.2illustratesabsolutevaluesoftrackdefectsforinterventionof

maintenanceteams.

16.6.3.Acceptancevalues

Aftertheexecutionofmaintenanceworks,somelowvaluesoftrackdefectscanbeleft,aslongasgeometricalcharacteristicsofthetrackcomplywiththevaluesillustratedinTable16.3.

16.6.4.Emergencyvalues

IftrackdefectssurpassemergencyvaluesasillustratedinTable16.4,animmediatereductionofpermittedspeedmustbeimposed,untilmaintenanceteamsinterveneandreducethevaluesoftrackdefects.

Table16.2.Limitvaluesofthevarioustrackdefectsforinterventionmaintenance

worksaccordingtosomerailways*(3mbasisfortracktwist,10mbasisforallothertrackdefects)

Table16.3.Acceptancevaluesoftrackdefectsafterexecutionofmaintenanceworks

Table16.4.Emergencyvaluesoftrackdefectsandmaximumpermittedspeed

16.6.5.LimitvaluesaccordingtoEuropeanspecifications

TheEuropeantechnicalspecificationsforinteroperabilitydealwithonlytwotrackdefects:variationsoftrackgaugeandtracktwist,(134).

Thelimitvaluesofvariationsoftrackgaugeforanimmediateaction(accordingtotechnicalspecificationsforinteroperability)aregiveninTable16.5,(134).

ThemaximumvalueoftracktwistaccordingtoEuropeanspecificationsis7mm/mfortrackspeeds≤200km/hand5mm/mfortrackspeed>200km/h.Asthebase-lengthforrecordingtracktwistmayvaryfromonetechniquetoanother,Europeanspecificationssetthelimitvalueoftracktwistinrelationtothebase-lengthofmeasurement(Fig.16.7),(134).

Inaddition,Europeanspecificationsprescribethatvariationsbetweennominalandrealvalueofcantshouldbeatmaximum±20mm,(134).

Table16.5LimitvaluesofvariationsoftrackgaugeaccordingtoEuropean

specifications,(134)

Fig.16.7.Limitvaluesoftracktwistinrelationtothebase-lengthofmeasurement,accordingtoEuropeanspecifications,forhigh-speedandconventionaltracks,(134)

16.7.Progressoftrackdefects

Wewillexaminenowhowaninitialtrackdefectwillevolveasafunctionoftrafficload.Knowledgeofthewaythattrackdefectsevolvemayhelpatimelyschedulingofremedialactionbytrackmaintenanceteams,beforethelimitspreviouslygivenareexceeded,(292),(293).

16.7.1.Longitudinaldefect

Aseriesoftestsandstatisticalanalyses,(301),(305),hasshownthatadefectpresentinatrackaftermaintenance,progressesrapidlyuptoacriticaltraffic

loadontheorderof2milliontons,beyondwhichdefectprogressismuchslower.Thismeansthatuptothistrafficloadthetrackhasnotfullystabilizedandshowssignsofinstability.Transverseresistanceofatrackaftermaintenanceisonly50%ofitsvalue,whenfullystabilized.

16.7.1.1.Meansettlementoftrack

Theevolutionofthemeansettlementoftrackisgivenbythefollowingempiricalformula,(305):

where:Tr=2·106tons,a1:meansettlementforatrafficloadTr,a0:settlementincreaserate(mm/decade),mainlydependingonsubgrade

quality,withmeanvalues2÷6mm/decade.

Theratio illustratestheslowprogressofthedefectafteratrafficloadof

2·106tonsisreached,andwasfoundtohavevalues0.25÷0.70,

Fig.16.8.Progressofthemeanvalueme(T)ofthetracksettlementasafunctionoftrafficload

16.7.1.2.Standarddeviationoflongitudinaldefects

Formedium-andhigh-speedtracks,thestandarddeviationoflongitudinaldefectssdLD(T)isusedasameasureofthequalityoftrack.Aseriesofstatisticalstudieshasyieldedthefollowingempiricalformula(ofaformsimilartoformula16.3),(305):

where:c1:standarddeviationoflongitudinaldefectsforatrafficloadTr=2·106t,c0:rateofincreaseofstandarddeviationoflongitudinaldefectsasafunctionof

trafficload,withmeanvalues0.1÷0.2mm/decade.

16.7.1.3.Intervalbetweenmaintenancesessions

Let bethelimitvalueoflongitudinaldefects,specifiedbythelimitssetinsection16.6.Fromequation(16.5)wededucethatthelimittrafficloadTlim

betweentwosuccessivemaintenancesessionswillbe:

Sincetheparameterc0isalmostconstant,thedeterminingfactorsforthetimeintervalTlimbetweentwosuccessivemaintenancesessionsaretheterms

andc1,thelatteramountingtothetrackconditionaftermaintenance.AnincreaseoftimeTlimisthereforepossiblebyimprovingtheinitialconditionofthetrackaftermaintenance,i.e.byabetterqualityoftrackmaintenanceworks.

Inthecaseofmedium-andlow-speedtracks,averagevaluesoflongitudinaldefectsareused,insteadofthestandarddeviationofthelongitudinaldefects,theformoftheaboveequationsremainingthesame.

16.7.2.Transversedefect

Transversedefectshaveapatternofevolutionsimilartoequation(16.5).Theevolutionofthestandarddeviationoftransversedefectsisgivenbythefollowingformula:

wherecoefficientsu1andu0(withmeanvalues0.1÷0.4mm/decade)aredefinedsimilarlytoc1,c0ofequation(16.5),(305).

16.7.3.Horizontaldefect

Trackloadingonthehorizontalplanediffersfromverticalloadingintwomainrespects:trafficloadeffectsaremuchmoreirregularanddiscontinuous,stressesdevelopedshould,forsafetyreasons,remainwithinelasticitylimits.

Likeothertypesofdefects,horizontaldefectsprogressrelativelyfastforaninitialtrafficloadTrontheorderof2·106tandthereafterslowdownconsiderably.Theirevolutionmayalsobeapproximatedbyasemi-logarithmicformulainrelationtotrafficload,which,however,inmanyinstanceshasshowndeviationsandalargedispersion.Thefollowingformulahasbeensuggestedfortheevolutionofthemeanvalueofthehorizontaldefects,(305):

wherecoefficientsd1,d0aredefinedasinequation(16.3),withmeanvaluesd1=0.6÷1.0mmandd0=0.15÷0.30mm/decade.

Theratio whichillustrateshowslowtheprogressofthe

horizontaldefectsisafteratrafficloadTr=2·106t.

16.7.4.Gaugedeviations

Gaugedeviationsmainlydependonsubgradeandrollingstocktypeandthereforetheirevolutionisdifficulttodetermineintermsofthevariousparameters.

16.7.5.Tracktwist

Evolutionoftracktwistisalsoofsemi-logarithmicform:

wherecoefficientsg0andg1(withmeanvalues0.2÷1.0mm/m/decade)havearatherlargedispersionandaredefinedasthoseofequation(16.5),(305).

16.8.Mechanicalequipmentformaintenanceworks

Modernrailwaytechnologyhasapanoplyofmaintenancemachines,ofwhichthefollowingcanbehighlighted,(289),(298):i)Heavyleveling,lining,tampingmachines,(Fig.16.9),whichshouldbeused,totheextentfeasible,onlyinscheduledmaintenanceoperations,wherelevelingandliningoperationsaresystematic.Anecessaryconditionforitsuseisthattheballastbesound,freeofsoilcontamination,ofpropergranulometricsizeandadequatemechanicalstrength.Theperformanceofsuchequipmentaveragesabout200÷300mperhour,althoughtheoreticalratesgivenbyconstructorsarearound800÷1,000moflengthoftrackperhour(andeven2,200mforexpresstampingmachines),(289).

Tampingistheoperationwherebytrackdefectsarerectifiedandincludesthefollowingstages:–Asurveyingteaminitiallydeterminestheelevationorhorizontalcorrection,whichshouldbegiventothetrack.

–Thetampingmachinemakesafirsttampingonthetrack.Itmovesthetrackleft,rightorup,dependingonthetrackdefects,whichshouldberectified.Itlowersthetampingbladesandcompactstheballastunderthesleeper,(Fig.16.9).

–Therecordingvehiclepassesandmeasurestheremainingdefects(acceptancetolerances),(seeTable16.3).Inadditiontotampingmachines,trackmaintenancealsorequiresother

machinery,suchas:Ballastcompactingandstabilizingmachines,whichfollowthetampingmachinesandcontributetotheincreaseofthestabilityandtransverseresistanceofthetrack.Ballastprofilingmachines,whichgivetheballasttheappropriatecross-sectionprofile,(Fig.16.10).Ballastcleaningmachines,whichareusedwhensmallsize(<22mm)ballastgrainsaremorethan30%ofthetotalballastvolume.Theballastcleaningmachineremovestoadepthof25cmbeneaththesleeperallballaststonessmallerthan35mm.Theperformanceofcleaningmachinesisaround400moftrackperhour,(289).

Fig.16.9.Tampingmachineinthecourseoftrackmaintenance

Fig.16.10.Ballastprofilingmachine

Formationrehabilitationmachines.Asdiscussedinsection9.1,agooddesignofthesubgradeshouldresultinnoneedtointerveneduringtherenewalofballast.However,insomecasesimprovementofthebearingcapacityofthesubgradeisnecessaryandisconductedwiththeformationrehabilitationmachines,whichinsertinthetopofthesubgradeanadditionalformationlayerconsistingofablendofsandandgravel.

ii)Light(portable)tampingmachines,theuseofwhichalsorequiresasoundballastmaterial.Sincethisequipmentiseasilytransported,itishighlyflexibleandshouldbeemployedin:

•limitedoperationsondiscontinuoussectionsofthetrack,ofuptoabout300minlength,wheretheuseofheavymachinerywouldbein-appropriateandexpensive,

•repeattampingonparticularsectionsofthetrack,•levelingofswitchesandcrossings,•(asanexceptiononly)forthesystematicmaintenanceoftracksections,whereheavymachineryisnotavailableorisunabletobeusedinthatparticulartrack.

iii)Handtoolssuchasthefork,thepickaxe,etc.,whicharenowconsideredvirtuallyobsolete,butcanstillbeusedinthefollowingcases:ontracksectionswithballastinastateofadvanceddisintegration,wheremechanicaltampingisnotpossiblewithoutaddingnewsoundballast,inthecaseofisolated,localandurgentrepeattamping,wheretheextentoftheoperationdoesnotjustifytheuseofevenlightballasttampingequipment.

Maintenanceoftrackwiththeuseofonlymanualmeansmayresultintentimesormoreman-hoursrequiredcomparedtofully-mechanizedmaintenance(289).

Duringscheduledmaintenancesessions,thetrackequipmentisinspectedandanydamageisrectified.Forthispurpose,thefollowingequipmentisused:–boltandscrew(bothscrewingandunscrewing)machines,–machinesfordrillingholesintotimbersleepers,–railcuttingmachines,–machinesfordrillingholesinrails,etc.,–railgrindingmachines,inordertosmoothirregularitiesattherailsurface,whichcanbearesulteitheroftrackdefects(short-pitchcorrugations,seesection10.9.4.4)oroftrainoperation.Thegrindingofrailcanbeachievedwiththehelpofeitherrotatingstonesorofstonesoscillatinglongitudinally,(290).Grindingofrailmaybenecessaryatanymomentbetweensuccessivemaintenancesessions,andtheexperienceoftracksinEuropesuggeststhegrindingofrailsonceper1÷3yearsofoperation,inrelationtotrafficload.

16.9.Schedulingofmaintenanceoperations

Railwaysarepeculiarinthattheyconsistofdiscretesubsystems,theinteractionsofwhichareneithersimpleandobviousnoreasytoanticipate.Figure16.11

illustratesablockdiagramoftheentiremaintenanceprocedureandtheparametersinvolved.Inthischarttwoprocessesareapparent,eachopposingtheother,(298),(304):•Thetrafficprocess,which,bythetrack-rollingstockinteraction,tendstoincreasetrackdefectsandtodestabilizethesystemasawhole,

•Themaintenanceprocess,whichstrivestoreducedefectsandrestorethetracktoitspreviousgoodcondition.

Thetwoabovementionedprocessesshouldbeinequilibrium,whichincidentallyisthebasicpurposeofmaintenanceworks.Thisequilibriumcanbeachievedonlybytimelyandrationalscheduling,which:

Fig.16.11.Blockdiagramoftheinteractionsbetweenthevarioussubsystemsandparametersdeterminingmaintenanceoperations,(304)

isbasedonsystematicallysortedinformationfrompastmaintenanceoperations,optimizestheuseofthemechanicalequipment,assignsprioritiescorrectlyalongtherailwayinfrastructure,onbothregionalandlocallevels.

Figure16.12illustratesaflowchartofthesuccessivestagesoftrackmaintenanceandrenewal.Inordertomakeamoreefficientuseofboththehumanandmechanicalresources,itisnecessarytodrawupsuchdiagramsbothatthestrategicmanagementlevelandduringmaintenanceworks.Telematicscanalsocontributetoarationalschedulingoftrackmaintenance,(294).

Formaintracks,thetampingofballastisconductedonceper3÷5yearsofoperation,whileballastreplacementandrenewalisconductedonceper15÷30years,dependingonthestrengthandmechanicalpropertiesofballast,andthetrafficoftheline.

16.10.Technicalconsiderationsfortrackmaintenanceworks

Whenperformingmaintenanceoperations,thefollowingconsiderationsshouldbekeptinmind:–Levelingadjustmentismandatorywithanyhorizontaloperation,nolaterthanthenextdayandinanycasebeforethetrackstabilizes.

Fig.16.12.Flowchartofthevariousplanningandimplementationstagesoftrackrenewalandmaintenanceoperations

–Ifthelevelingadjustmentisperformedbyheavymachinery,themachineshouldperformhorizontaladjustmentsimultaneously.

–Ifthelevelingadjustmentisperformedbyheavymachinery,noadditional

elevationadjustmentsshouldbemadebeforetrackstabilization,whichisbroughtaboutbylinetraffic.

–Intheeventthat,aftertheelapseofthestabilizationperiod,defectsnotcompletelyrectifiedarestillfound,supplementaryadjustmentsshouldbeperformedbylightequipment,withouthavingtore-liftanyelevatedsectionsofthetrack.Wehaveseenintheforegoingthataftermaintenance,asensitiveperiod

follows(untilatrafficloadontheorderof2milliontons),duringwhichdefectsevolverapidly.Onlineswithmedium-trafficload(groupUIC4),thisperiodcorrespondstoabout1÷4months.Onlineswithhightraffic(groupsUIC1,2,3)thisperiodcorrespondsto15÷40days.Duringthistime,thetrackshouldbetheobjectofcontinuousandcarefulattention,consistingofthemonitoringoftheprogressofthevariousdefectsandtimelylocalinterventionswithlight(orheavy,ifnecessary)machinery,wheneverdefectaccumulationisunusualorexcessive.Thesensitiveperiodaftermaintenanceisthereforethekeytotracklongevityandtothereductionoffuturemaintenanceexpenses.Ifthemeasuresmentionedabovearenottakenduringthisperiod,problemswillfrequentlyariselaterandincreasedeffortswillberequiredtorestoretrackgeometry,(297).

16.11.Optimizationofmaintenanceexpenses

Themaintenanceoftrack(butalsoofrollingstockandsignalingsystems)isessentialforsafeandcomfortablerailtransport,whichshouldberealizedatthelowestpossiblecost.Asanalyzedinsections6.1and7.2,allproblemsofrailwaysshouldbeexaminedwithinasystemsapproachandwithinthelifecycleofrailways,whichmaybeaslongas50yearsforrailsorshorterforothercomponents.Rationalizationandoptimizationofpartialcostscanbeachievediftheyareintegratedwithinthefollowingtwoconcepts:•thelifecyclecostofarailcomponent,whichisunderstoodasthesumofallexpensesrequiredtosupportthespecificcomponentfromitsconceptionandfabrication,throughitsoperationtotheendofitseconomiclife,(291),

•thelifecyclecosting,whichisamethodologyofsystematiceconomicevaluationoflifecyclecostsofallrailcomponentsandproceduresoveraperiodofanalysis,(291).

•aglobalconceptionoftherailwayproduct,knownundertheinitialsRAMS,whichassures:–Reliability,understoodastheprobabilitythatarailcomponentcanperform

itsrequiredfunctionsundergivenconditionsandforagiventimeinterval,–Availability,understoodastheabilityofarailcomponenttoperformitsrequiredfunctionsundergivenconditionsatagiventime,providedthattherequiredexternalresources(human,funding)areensured,

–Maintainability,understoodastheprobabilitythatamaintenanceactionofarailcomponentcanbecarriedoutundergivenconditionsofuse,withinastatedtimeintervalandusingstatedproceduresandresources,

–Safety,understoodasthefreedomfromunacceptableriskofharm.

Themaintenanceoftrackwasconducteduntilsomedecadesagoalmostexclusivelybyrailwaypersonnel,withtheuseofequipmentthatbelongedtotherailwaycompany.However,inrecentyears,someinfrastructuremanagersprefertooutsourcepartorallthemaintenanceactivityoftrack(seealsosection6.6.3).Ifsuchaprocedureofoutsourcingisdecidedupon,specialattentionshouldbepaidatthefollowing:

•criticaltermsofthecontractofoutsourcing(suchasdeliverydate,unpredictedevents,realtotalfinalcost,etc.)shouldbeanalyzedindetailbyusingsensitivityanalysis,

•makesurethatbothtotalcost(overthewholelifecycle)andqualityoftrackarebetterfortheinfrastructuremanager,whenoutsourcingthespecificactivity,

•quantifytheprobabilitythattheservicewillnotbedeliveredinaccordancewiththerequirementsandforeseealternativesolutionsinthecaseofdelays,failure,etc.,

•identifyalleventualrisks,trytolimitthemandprovidealternativesolutions.

16.12.Trackmaintenance,vegetationandweedcontrol

Theissueofvegetation,appearingalongthetrack,wasanalyzedinsection9.16.Weedscancauseseriousdetrimentaleffectsontheballastandthesubgradeby:•contaminatingtheballastwithdirtandvegetationdebris,whichaffectfreedrainage,

•acceleratingthedecayofcomponentssuchasconcretesleepers,notonlybychemicalactionbutbytheexpansionofrootsincracksandcrevices,

•byobscuringthetrack,andthusdefectsnormallyobservedbythenakedeyewouldnothavebeenseenonroutinevisualinspections.

Arsenic-basedchemicalswereintroducedforweedcontrolinthe19thcentury,andcontinuedtobeusedinvaryingdegreesinsomecountriesuntilthe1930s,butarenotusedtoday.Duringthe1930s,sodiumchloratewasintroducedasachemicalweedcontrol,andwiththeadditionoffiredepressants(suchascalciumchloride)wasmadereasonablysafewithoutanytoxiceffect.Since1950,herbicideshavebeenextensivelyused,particularlyhormoneselectiveweedkillers.

Applicationratesare1÷20kg/hectare,theaveragebeing4÷8kg/hectare.Herbicidesmustbeappliedevenlyoverthearea,atthelowestpracticalvolumeperhectareifinliquidform,atthegreatestpracticalspeed,withmaximumsafetyandtakingallmeasurestopreventanyenvironmentalharm.

Spraytrainscanalsobeused.Theircapacitycanreach300km/day(thedailyaverageobservedoverafourmonthseasonintheUKwas130km/day),(302).

*DB:Germanrailways,SNCF:Frenchrailways,NS:RailwaysofNetherlands,BR:(former)Britishrailways,UIC:InternationalUnionofRailways

17SlabTrack

17.1.Thedilemmabetweenballastedandnon-ballastedtrack

17.1.1.Advantagesandweaknessesofballastedtrack

Untiltheearly1970s,railwaytracksallovertheworldwerelaidonballast,whichisreplacedevery15÷30years,whereasthemaintenanceoftracktakesplaceevery3÷5years.Maintenanceandrenewalofballastareconductedunderextremelydifficultconditionsintheintervalsbetweensuccessivetrains,usuallyduringthenight,andtheavailabletimeformaintenanceorrenewalworksisusuallysmallerthan3÷5h.

Theincreaseofspeedbeyond200km/hresultedinadisproportionatelygreaterincreaseofmaintenancecosts,whichforhigh-speedtracksarealmostdoublethatofconventionaltracks(V<200km/h).Althoughballastedtrackhassufficientmechanicalcharacteristics(hightransverseresistance,lowstressesandsettlements),lifecycleandmaintenanceconsiderationsorientedrailwaymanagersandengineerstotheuseofaslabtrackinsteadofballastedtrackonseveraloccasions.

However,theballastedtrackhastheadvantageofensuringahighflexibilityofthetrack,muchlowerconstructioncost,thepossibilityofeasilyrectifyingthetrackdefectsordifferentialsettlements,theabsorptionofdynamiceffects,andemissionoflowerlevelsofnoise(comparedtoslabtrack),(314).

17.1.2.Thenon-ballastedtrack

Innon-ballastedtrack,aconcreteslab(reinforcedorprestressed)oranasphaltlayerreplacestheballastandtherailcanlieeitherdirectlyontheslaboronsleepers,whichintheirturnlieonaconcreteslab.Belowtheconcreteslab,aballastconcretelayer,andananti-frostlayerareinterposed,(312),(Fig.17.1).

Thus,thenon-ballastedtrackusesaseriesofsuccessivelayersinordertograduallyreducestressesfromrailtosubgrade,sothatstressvaluesatthesubgradearelowerthanitsbearingcapacity.

Fig.17.1.Non-ballastedtrack

Thebasicadvantageofnon-ballastedtrackisitslowmaintenancecostandexcellentanduninterruptedoperationconditions,incomparisontoballastedtrack.Inaddition,astheconcreteslabhasalowerthicknesscomparedtoballast,thenon-ballastedtrackresultsinareductionoftherequiredcross-sectionfortunnels,somethingthatreducestheoveralltunnelconstructioncost.Anon-ballastedtrackhasalonglifetime(50÷60years),morethandoublecomparedtoballast(15÷30years).Increasedtransverseresistanceandpassengers’comfortarealsoamongtheadvantagesoftheslabtrack.

However,non-ballastedtrackisnotfreeofdisadvantages,themostimportantbeingitshigherconstructioncost.Savingsinmaintenance,however,canrecoverthisadditionalcostoftheslabtrackwithinanumberofyears,dependingontheeconomicconditionsofeachcountry.

Oncetheslabtrackisinstalled,itisverydifficulttoovercomeeventualdifferentialsettlementsand,therefore,theuseofslabtrackmustberestrictedtoareaswhereagoodandconstantsubgradequalitycanbeprovided.However,whenslabtrackisused,noiselevelsarehighercomparedtoballastedtrack.

Aquestion,whichhasnotbeenansweredyet,iswhatwillhappenattheendofthelifecycleofaslabtrack(50÷60years)andhowcanafreshconcreteslabreplaceanoldonewithoutinterruptingtraffic?

17.1.3.Firsttrials,testsandevolutionofslabtracktechniques

Amongthefirsttrialsforslabtracktechniques,weretestsrunintheformerWestGermanyin1959andinJapanintheearly1960s.SlabtrackwasinvestigatedbytheResearchDepartmentoftheUICinatesttrackconstructedintheUnitedKingdomin1967forjustthispurpose.Thefirstslabtrackwasconstructedatthe

railwaystationofthecityofRhedaintheformerWestGermanyin1972.Duringthe1980sand1990sanincreasingnumberofkilometersofslabtrackwasconstructedinmanycountries,suchasGermany,Japan,theNetherlands,Italy,Korea,China,etc.

17.2.Mechanicalbehaviorofslabtrack

17.2.1.Simulationofslabtrack

Traditionalmethodssimulatedslabtrackasamulti-layersystem.Manyexperimentalresultshavehighlightedtheneedforamoreaccuratesimulation.

Thefiniteelementmethodcanbeusedfortheaccurateanalysisofthemechanicalbehaviorofslabtrack,(306),(307),(312).Figure17.2illustratesthemeshofsuchasimulation,(312).Inordertotakeintoaccountthedynamiceffectoftheproblem,whichmaybecriticalforslabtrackbutneglectedforballastedtrack,theequationofdynamicsisused:

inwhich:

M:themassmatrix,C:thedampingmatrix,K:thestiffnessmatrix,U:thedisplacementvector,R:thevectorofexternalloads,F:thevectorofforcesexertedonsystem’snodes,i:numberofiteration,t:time.

Applicationofthismodelhasbeenmadeinthecaseofaconcreteslabwithamaximumcompressivestrengthof300kp/cm2andasubgradeofgoodquality.

17.2.2.Stressesandsettlementsinthecaseofslabtrack

ThemodelpresentedinFigure17.2hasgiventhefollowingvaluesfortheverticalstressesundertheaxleload,(312):–betweensleeperandconcreteslab:1.96kg/cm2,–topofthesubgrade:0.60kg/cm2.

Asfarastheverticalsettlementundertheaxleloadisconcerned,themodelhasgiventhefollowingvalues:–topofconcreteslab:0.34mm,–topofthesubgrade:0.30mm.

Figure17.3illustratestheelasticlineoftheconcreteslab.

Fig.17.2.Meshforthesimulationofslabtrackwiththeuseofthefiniteelementmethod,(312)

Fig.17.3.Elasticlineoftheconcreteslab,(312)

17.3.Avarietyofformsofnon-ballastedtrack

Thevariousformsofnon-ballastedtrackcanbeclassifiedasfollows:

•slabtrackwithsleepers,whichareembeddedinareinforcedconcreteslab(Rhedatechnique)orinamonolithicconcreteslab(Züblintechnique).Thesetechniquesarenamedaftertheareaswheretheywereappliedforthefirsttime,

•prefabricatedslabtrackwithoutsleepers,amethodusedextensivelyinJapan,•sleepersplacedonanasphaltlayer,•embeddedrailsinaconcreteslab.

17.4.Slabtrackwithsleepers

17.4.1.TheRhedatechnique

IntheRhedatechnique,(Fig.17.4),ananti-frostlayerof30cmisplacedontopofthesubgradeandaboveita30cmthickballastconcretelayer,ontopofwhichareinforcedconcretetroughofathicknessof18cmisplaced.Monoblockortwin-blocksleepers,spaced65cmapart,areembedded,withtheuseoffillingconcrete,intheconcretetrough.

Theconcretetroughhasamechanicalcompressivestressof300kp/cm2forthecylindricaltest(equivalently370kp/cm2forthecubicaltest).Theballastconcretelayerhasameancompressivestressof150kp/cm2.Itsgranulometriccompositioncontainsgrainsgreaterthan2mmat55÷85%oftotalweightandgrainssmallerthan0.063mmatlessthan15%ofthetotalweight.

InrecentevolutionsoftheRhedatechnique,thesleepershaveaholethroughwhichsteelbarsareplacedlongitudinallyinordertoavoidloosening.TheRhedatechniquehasbeenusedextensivelyinopentrack,tunnels,andbridgesinGermany.

TherecordingoftrackdefectsonaslabtrackoftheRhedatypegavesmallervaluesofthevariousdefects,comparedtotheballastedtrack.Inparticularthetrackgaugehasremainedconstant,whereasinaballastedtrack,greatergaugevariationshavebeenrecorded,(311).

Fig.17.4.TheRhedatechnique

17.4.2.TheZüblintechnique

TheZüblintechnique,(Fig.17.5),differsfromtheRhedatechniqueinthatthemonoblockortwin-blocksleepersareembeddeddirectlyinamonolithic20cmthickconcreteslabwithamechanicalcompressivestressof300kp/cm2

forthecylindricaltest(equivalently370kp/cm2forthecubicaltest).IntheZüblintechnique,sleepersarepositionedinthefreshconcrete,whereasintheRhedatechniquetheconcreteslabisalreadyconstructedandsleepersarepositionedontheconcreteslabwiththeuseoffillingconcrete.TheZüblintechniquehasbeenextensivelyusedinGermanyandtheNetherlands.

Fig.17.5.TheZüblintechnique

17.4.3.TheStedeftechnique

IntheStedeftechnique,(Fig17.6),sleepersarepositionedonanalreadyconstructedconcreteslab.Arubberlayer4.5mmthickisplacedbetweenthesleeperandtheslab,(314).TheStedeftechniquehasbeenusedintunnelsinFranceandintheChannelTunnel.

Fig.17.6.TheStedeftechnique

17.5.Slabtrackwithoutsleepers

Inslabtrackwithoutsleepers,therailsarepositioneddirectlyonprefabricatedprestressedconcreteslabs,(Fig17.7).Inordertoabsorbtheincreaseddynamiceffects,anasphaltroadbedofathicknessof40cmisinterposedbetweentheslabtrackandtheroadbed.ThistechniquehasbeenextensivelyusedinJapan,withhorizontaldimensionsoftheslabof4.95m×2.34mandathicknessof16cmintunnelsand19cminopentrack.AsillustratedinFigure17.7,cylindricalstoppersareusedinordertopreventlateralandlongitudinalmovementsofthetrack.

AvariationoftheJapanesetechniqueistheBögltechnique,(Fig.17.8),withgeometricaldimensionsoftheprefabricatedslabof6.45m×(2.55÷2.80)m,athicknessof20cmandacompressivestressof450kp/cm2forthecylindricaltest(equivalently550kp/cm2forthecubicaltest).IntheBögltechnique,slabsareofreinforcedconcreteinthelongitudinaldirectionandofprestressedconcreteinthelateralone,(309).

Inthecategoryofslabtrackwithoutsleepers,wecanalsoconsidertheembeddedrailtechnique,(Fig.17.9),inwhichbetweentherailandtheconcreteslabisinterposedanelasticmaterial,(313).

Fig.17.7.Slabtrackwithoutsleepers(Shinkansentechnique)

Fig.17.8.TheBögltechnique

Fig.17.9.Theembeddedrailtechnique

17.6.Non-ballastedtrackonanasphaltlayer

Ballastmaybereplacedbyanasphaltlayer,(Fig.17.10),ofathicknessof25÷30cm,ontopofwhichsleepersarepositioned.Asphalthasthesamemechanicalcharacteristicsasinroadengineeringandisplacedinsituwiththeuseofsimilarequipment.

Fig.17.10.Non-ballastedtrackonanasphaltlayer

17.7.Transitionbetweenballastedandslabtrack

Slabtrackhasahigherstiffnessandalowerflexibility,comparedtoballastedtrack.However,overalltrackqualityandpassengers’comfortcannotchangefromonekilometricpointtoanother.Forthisreason,atransitionzonebetweenballastedandslabtrackshouldbedesignedascarefullyaspossible.Eachslabtracktechniquehasitspeculiaritiesforthetransitionzone.Figure17.11illustratesatransitionzonedesignfortheRhedasystem,inwhich:–thetransitionzonehasaballastedtracksectionandaslabtracksection,–inthetransitionslabtracksection,theballastconcretelayerundertheslabtrackisextendedfrom30cmto50cm,

–inthetransitionballastedtracksection,ballastgrainsandstonesarestucktoeachother.InthepartABofthissection,(Fig.17.11),theballastconcretelayerisextendedandpartiallyreplacesthesubballast,whereasintheotherpartBCthesubballastlayerisextended,

–twoauxiliaryrailsareplacedalongthetransitionzoneintheinnerpartofeachrunningrail,

–theanti-frostlayerisalsoextendedtoasignificantpartofthetransitionzone.

Fig.17.11.Transitionbetweenballastedandslabtrack

17.8.Costsofslabtrack

Slabtracksaredesignedwithatopspeedof250÷350km/hforhigh-speedrailwaylinesand160km/hformetroandsuburbanrailwaysystemsandanestimatedlifecycleof50÷60years.InGermany,constructioncostoftheslabtrackisreportedat680€/mfortheRhedatechniqueandat575€/mfortheZüblintechnique,againstacostof365€/mforballastconstruction(allvaluesofyear2008).Thesecostsdonotincludetheincreasedearthworkandsubgradecostsforslabtrack.Thecostofnon-ballastedtrackonanasphaltlayerisaround630€/m.InFrance,constructioncostsforslabtrackarereportedtobedoublethatofballastedtrack.

TheconsiderationofagreatnumberofslabtracksystemsinGermanyrevealedmaintenancecostsapproximately10%comparedtoballastedtrack,whereasinJapanmaintenancecostsofslabtrackamountto20÷30%ofmaintenancecostsofballastedtrack,(308),(310).

TheCologne–Frankfurttrack,constructedin2002totallyonaconcreteslabwiththeuseoftheRhedatechnique,hadanaverageconstructioncostof21.7million€/kmoftrack,(seealsosection5.2,Table5.1).

18TrainDynamics

18.1.Traintraction

Inatrain,thelocomotive,whichprovidesthetractiveforce,isusuallydistinguishablefromthosevehiclesbeinghauled.Thelocomotivemaybepoweredbyeitherinternal-combustion(diesel)engines,inwhichcasethereisdieseltraction,(seesection20.4),orbyelectricmotors,inwhichcasethereiselectrictraction,(seesection20.5).

Thehauledvehiclesconsistofthevehiclebody,carryingpassengersorfreight,andthewheels.Thebodyissupportedbythewheelseitherdirectlyontheiraxles,(seesection19.3),oronbogies,(seesection19.4).Wheelswhichprovidetractionarereferredtoasdrivingwheels,whereaswheelswhichdonotprovidetraction,areknownastrailingwheels.

Thedistinctionbetweentractiveandhauledvehiclesislessclearindiesel-electric-poweredvehicles,whereonlycertainoftheotherwiseidenticalpassengervehicleshavedrivingwheels.

Inordertoensuretrainoperationataparticularspeed,adequatetractiveforceshouldbeprovidedtoovercomethevariousforcesresistingtrainmotion.

18.2.Resistancesactingduringtrainmotion

Duringtrainmotion,resistanceforcesdevelop,whichthetractiveforcemustovercome.Theseresistanceforcesare:–runningresistanceRL(mechanicalandaerodynamic)inhorizontalrectilinearmotion,

–resistanceRccausedbytrackcurves,–graderesistanceRgcausedbygravityongradients,positivewhenmovinguphill,negativewhenmovingdownhill,

–inertial(oracceleration)resistanceRincausedbyinertiaduetoaccelerationonstartingandwhenspeedisnotconstant.

TotalresistanceRisthesumofRL,Rc,Rg,Rin.Theresistanceperunitweightofrollingstockiscalledspecificresistancer.

Manyoftheformulasgivenbelowareempiricalorsemi-empiricalandincludecoefficientswithvaluesfoundforaparticulartypeofrollingstock(e.g.,BR:(former)Britishrailways;DB:Germanrailways;SNCF:Frenchrailways,etc.)andforspecificoperatingconditions.

18.3.RunningresistanceRL

18.3.1.Generalequationfortherunningresistance

Runningresistanceisgivenbythegeneralequation(18.1),(322),(324):

Inthisequation:ThetermsA+B·Vincludethevariousmechanicalresistances.ThefirsttermA(whichdoesnotdependonspeed,butonlyonrollingstockcharacteristics)representstherollingresistancesandthosegeneratedbyfrictionbetweenthewheelflangeandtherailoncurves.ThesecondtermB·Vrepresentsthevariousmechanicalresistances,whichareproportionaltospeed(rotationofaxlesandshafts,mechanicaltransmission,braking,etc.).ThethirdtermC·V2representstheaerodynamicresistances.

TheparametersA,BandCcanbeexpressedasfunctionsoftherollingstockcharacteristicsbythefollowingformulas(RLinkg,Vinkm/h),(324):

where: M:

totaltrainmass(tons)

m:

massperaxle(tons)

λ:

parameterwithvaluesdependingontherollingstocktype,e.g.forSNCFvehicles0.9<λ<1.5

Informula(18.4),thefirsttermrepresentstheaerodynamicresistancesarisingatthetrainfrontandrearandthesecondtermrepresentstheaerodynamicresistancesgeneratedalongthesurfacep·L,

where: k1:

aparameterdependingontheshapeofthetrainfrontandrear.Forinstance,inconventionalmedium-andlow-speedSNCFrollingstock,k1=20·10-4,whileforTGVtrains,k1=9·10-4,(324),

S: frontsurfacecross-sectionalarea(inm2)(commonlyaround10m2),

k2:

parameterdependingontheconditionofthesurfacep·L.Asanexample,inconventionalSNCFrollingstock,k2=30·10-6,whileforTGVrollingstock,k2=20·10-6,

p: partialperimeter(inmeters)oftherollingstockdowntotheraillevel,withcommonvaluesaround10m,

L: trainlength(m).

Figure18.1illustratestheincreaseofmechanicalandaerodynamicresistancesasafunctionofspeed.Wecanremarkthatathighspeedsaerodynamicresistanceiscrucialandtrainsaregivenasuitableaerodynamicshapeinordertoreduceit,(316).

Figure18.2illustratestherunningresistanceasafunctionofspeedandthepowerrequiredtoovercomethisresistance.Weseethatinordertoincreasespeedfrom200to300km/h,enginepowerhastobeincreasedbyabout200%.

Fig.18.1.Mechanicalandaerodynamicresistancesasafunctionofspeed,(48)

Fig.18.2.Runningresistanceandrequiredtractionenginepower(atzerogradient)asafunctionofspeed(caseoftheFrenchTGV),(327)

18.3.2.Empiricalformulasofsomerailwaysfortherunningresistance

ThevaluesofparametersA,B,Cofequation(18.1)dependonthecharacteristicsandpeculiaritiesoftherollingstock.Thevariousrollingstockmanufacturersandthevariousrailwayshavedevelopedempiricalformulasfortheseparameters.Formulasinusebyvariousrailwayauthoritiesworldwidearegivenbelow.

18.3.2.1.FormulasoftheFrenchrailways

18.3.2.1.1.Dieselorelectriclocomotives

Therunningresistanceisgivenbytheempiricalformula,(325),(330):

where: L: locomotiveweight(tons), n: numberofaxles, V: speed(km/h).

18.3.2.1.2.Hauledrollingstock

Duetothedissimilarityofthehauledrollingstocktypes,thevariousformulaspresentalargespread;theyaresimplifiedbymergingthetermsB·VandC·V2ofequation(18.1).Thecommonpracticeistocalculatethespecificrunningresistancer.Therefore,(325):•Forpassengerrailvehiclesonbogies:

•ForstandardizedUIC-typevehicles:

•Forpassengervehiclesonaxlesandexpressfreighttrainvehicles:

•Forblockfreightvehicles:

18.3.2.1.3.Electricpassengervehicles

Electricpassengervehicles(includingtractionmotors)arecommonlyusedinhigh-speedtrainsandinsuburbancommuterservices.ThetotalrunningresistanceRLinthecaseofelectriccommutertrainscanbecalculatedbytheformula,(325):

with:P

:totalmassoftheelectricpassengervehicle(intons),

m:

massperaxle(tons),

V:

speed(km/h),

S,p,L:

asinequation(18.4),(section18.3.1),

N:

numberofraisedpantographs,(seesection20.8.5).

18.3.2.2.FormulaoftheAmericanrailways

Americanrailwaysusethefollowingformulaforthespecificrunningresistance,(320):

where:

1lb :0.454kg,lts :shortton=2,000lbs=907.2kg,

M :trainmass,m :massperaxle,n :numberofaxlesintrain,mph :milesperhour(=1.61km/h),k :C·S,C :airresistancecoefficient(fromtables),S :vehiclecross-sectionalarea(insquarefeet).

Fig.18.3.SpecificrunningresistanceaccordingtotheAmericanrailways,(320)

Figure18.3illustratesthespecificrunningresistancesforvariousrollingstocktypes:

intercitytrains,V=80mph,m=25lb/axle,traincompositionof16vehicleswithatotalmassof1600ts,mixedfreighttrains,V=60mph,m=15lb/axle,averagevehiclemass:45ts,totaltrainmass:3,000ts,blockfreighttrains,V=60mph,m=60lb/axle,trainof21vehicles,each240ts.

18.3.2.3.FormulasoftheGermanrailways

TheGermanrailwaysusetheStrahlformulaforfreighttrains,(Fig.18.4),(320):

andtheSauthoffformulaforintercitytrains:

where:k :0.5formixedfreighttrainsand0.25forblocktrains,V :trainspeed(km/h),ΔV :headwindspeed(ittakesusuallythevalue15km/h),a :coefficienttakingthevalue1.0forrollerbearingandthevalue1.9

forplainbearing,Fe :coefficientrelatedwithtrainfrontareacharacteristics,taking

usuallythevalue1.45,nw :numberofwagons,

W :trainmass(intons).

Figure18.4illustratesthespecificrunningresistanceforvariousrollingstocktypesaccordingtotheGermanrailways.

Fig.18.4.SpecificrunningresistanceaccordingtotheGermanrailways

18.3.2.4.Formulasforbroadandmetricgaugerailways

Forbroadgauge(e=1.676m)railways,thefollowingformulashavebeensuggested,(Fig.18.5),(320):•passengertrains

•freighttrains

Formetricgauge(e=1.000m)railways,thefollowingformulashavebeensuggested,(Fig.18.6),(320):•passengertrains

•freighttrains

Fig.18.5.Specificrunningresistanceforbroadgaugerailways

Fig.18.6.Specificrunningresistancefornarrowgaugerailways

18.3.3.Resistancesdevelopedwhenrunninginatunnel

Comparedtoopenairoperation,operationinatunnelhascertainpeculiaritiescausedbysuddenincreasesinpressure(withanunfavorableinfluenceonpassengercomfort),increasedaerodynamicresistances,problemsarisingwhentrainscrossandfinallytheneedtoensureproperventilation.

18.3.3.1.Pressureproblems

Whenatrainentersatunnel,thefrontsection(thehead)ofthetraincompressestheairattheentrance,givingrisetoacompressionwave,(Fig.18.7),theamplitudeofwhichincreasesasthetrainproceeds,reachingamaximumwhentherearsection(thetail)ofthetrainentersthetunnel.Atthismomentthevacuumleftbehindthetraincreatesadepressionwave.Thecompressionwaveatthetrainfront,whichpropagatesatthespeedofsoundalongthetunnel,isreflectedbytunnelwallsandreturnsintheformofadepressionwave.Withrespecttothedepressionwavegeneratedbythetailofthetraininsidethetunnel,itundergoescorrespondingchangesandfinallyreturnsintheformofacompressionwave.Whenallthesewavesaresuperposed,theygiverisetopressurefluctuationsprogressivelydiminishinginamplitudeasafunctionoftime,(48),(317).

Fig.18.7.Compressionanddepressionwaveswhenatrainentersatunnel

Itshouldbenoted,however,thatpassengerdiscomfortiscausednotsomuchbypressurevariationsasbytherateofpressurevariation.Duringabruptchangesofweatherthepressuremaychangebyupto1,300mmH2O,anda1,000mincreaseinaltitudecausesapressuredropof1,100mmH2O,withnosignificantdiscomfort.Incontrast,duringtrainmotioninatunnel,pressurechangesaremuchsmallerbutalsomuchmoreannoying.Thereasonlieswiththepressurechangerate.Thehumanbodycanadapttosignificantchangesinpressure,providedthattheyarenotabrupt,(328).

Factorsaffectingpassengercomfort,therefore,includebothpressurevariationΔpandpressurevariationrateΔp/Δt.Variousresearch,(328),hasshownthatpassengercomfortisnotsignificantlyaffectedaslongas:

wherecisaconstant,thevalueofwhichisdifferentinthevariousrailwayauthorities.

Figure18.8illustratesrecordedvaluesofpressurevariations,whichdependgreatlyonrollingstockcharacteristics.Weseethat,untilaspeedof220÷240km/hisreached,passengercomfortisnotsignificantlyaffected.Beyondthisvalue,however,pressurevariationsandtheirratesofchangebecomeimportant.

Fig.18.8.Pressurevariationandpressurevariationrateasafunctionofspeed,(328)

18.3.3.2.Increasedaerodynamicresistancesintunnels

Inordertoreduceincreasedaerodynamicresistancesintunnels,lateralopeningsaremadealongthetunnelwithspectacularresults,(Table18.1).

IntheChannelTunnel,whichiscomposedoftwosingle-tracktunnels,lateralopeningsevery375mresultedinareductionofthepowerrequiredtoovercomeaerodynamicresistancefrom13.5MWto5.8MWataspeedof140km/h,(seealsosection2.4),(48).

Table18.1.Comparativerunningresistanceforatrainweighing705tintunnelswith

andwithoutlateralopenings,(325)

Inordertoreducetheaerodynamicresistancesintunnels,effortsaremadetoreducetheS/Σℓratio,whereSisthefrontsurfacecross-sectionalareaofthetrainandΣℓtheeffectivetunnelcross-sectionalarea,(Fig.18.9).Thus:

Fig.18.9.Effectivetunnelcross-sectionΣℓ

ItisevidentthatanexcessivereductionintheS/Σℓratiowouldleadtoaninordinateandexpensiveincreaseoftunnelcross-section.

18.3.3.3.Crossingoftrains

Whenatraincrossesanotherinatunnel,compressionwavesgeneratedbythefirststriketheotherandconversely.Asthefastertraingivesrisetothestrongereffects,theslowertrainisobviouslysubjectedtogreaterstresses.

TestsconductedbytheItalianrailwayshaveshownthataerodynamiceffects

whentwotrainscrossinatunneldonotaffectsignificantlypassengercomfort,mainlybecauseoftheirshortduration(afewtenthsofasecond),(328).Humanhearingisdisturbedbyextraneousinfluencesonlyiftheylastlongerthanhalfasecond.Withrespecttodamageoftherollingstock,(mainlyeventualfractureofwindowglasses),theabovetestshaveshownnosignificantriskathighspeeds,(328).18.3.3.4.Tunnelcross-sectionrequirementsathighspeeds

Alltheaforementionedreasonsentailthatthetunnelcross-sectionincreasesasspeedincreases.Table18.2givestheeffectivecross-sectionalareaΣℓforvariousspeedsandfordouble-tracktunnels,whereasFigure18.10illustratesthedimensionsofatunnelwitharunningspeedof300km/h.However,inthedesignofhigh-speedtunnels(V>200km/h),emphasisshouldbeputnotonlyonthedistancebetweentracks(4.20÷4.70m)andthecross-sectionalareaΣℓ(80÷100m2)butalsoontheperformanceandmechanicalresistancesoftherollingstock(particularlytheglassparts).

Table18.2.Requiredtunnelcross-sectionalareaΣℓforadouble-tracktunnelatvarious

speeds,(318)

Fig.18.10.Cross-sectionofahigh-speedtunnel

18.3.4.Comparativerunningresistancebetweenrailwaysandroadvehicles

Therunningresistanceofarailvehicle(passengerorfreight)isfarlowerthanthatofaroadvehicle,fivetimeslowerforpassengertransportandfourtimeslowerforfreighttransport.Thelowerrailwayrunningresistanceisfirstlyduetothelowercoefficientoffrictionofthemetalwheelsonmetalrailsandsecondlytotheloweraerodynamicresistanceofatrainbecauseofitsgreatlength.

18.4.ResistanceRcduetotrackcurves

Additionalresistanceoncurvesiscausedby:–frictionbetweenwheelflangeandrail,–wheelslippageontherails,sincetheaxlesofabogieorofatwo-axlerailvehiclearealwaysparallel.

Thespecificresistancerc,occurringalongcurves,canbeexpressedbythefollowingformula,inusebySNCF:

where:k:parameterwithvaluesbetween500÷1,200,theaveragebeing800,R:

radiusofcurvatureinthehorizontalplane(m).

18.5.ResistanceRgcausedbygravity

Inarailvehiclerunningalongastraightleveltrack,theforcecomponentperpendiculartothedirectionofgravityiszero.However,whentheplaneofthetrackisinclined(e.g.whenthetrainisrunninguphillordownhill),aforcecomponentRgdevelopsparalleltotheplaneofthetrack,(Fig.18.11),andinthecaseofanuphillgradientthiscomponentisanadditionalresistancetovehiclemotion.

Fig.18.11.Gravityresistance

Asthelongitudinalgradientofrailwaytracksissmallandseldomexceeds20‰,theangleωisverysmallandthereforeitcanbeassumedthatsinω=tanω.Consequently:

whereiisthelongitudinalgradient.

Resistancesduetolayoutcurvesandtogravityarecommonlyunifiedinacommonterm.

18.6.Inertial(acceleration)resistanceRin

Resistanceforcesarisingfromtheaccelerationofatrainaregivenbytheequationofdynamicsanddependontherollingstockgeometryandthematerialofwhichthevehiclesaremade.Inertialresistanceisproportionaltothetrainmassandtheacceleration.

Ifαistheacceleration,thespecificinertialresistancerincanbefoundfrom

theformula:

where:q:amasscoefficienttakingintoaccountboththefixedandtherotatingmassesoftherollingstock,suchasshafts,electricmotors,etc.

IfMrotaretherotatingmassesandMthetotaltrainmass,then:

Measurementshaveshownthatanaccelerationof1cm/sec2resultsinaninertialresistanceof1kg/t,whichisapproximatelyasmuchasthatfromanuphillgradientof1‰.

18.7.Startingforceandtractionforceofatrain

StartingforceistheforcerequiredtoputatrainintomotionandisdenotedasZstart.Thestartingforceshouldovercomethesumofallresistancesgeneratedduringtrainmotion.Ifallvehiclesofatraindepartedsimultaneously,thestartingforcewouldhavetobeveryhigh.Inpractice,however,thisisneverthecase,sincethetraindoesnotstartasablock,duetothegapsbetweenthesuccessivevehicles.Oncethetraindeparts,theforcenecessarytocontinueitsmotioniscalledtraction(ortractive)forceZandismuchsmallerthanthestartingforce.IfZreferstotheforcerequiredpertonofrollingstock,thenitiscalledspecifictractionforcez.

Fig.18.12.TractionforceZ–runningspeedVdiagramofadieseltrain

Fig.18.13.TractionforceZ–runningspeedVdiagramofanelectrictrain

Indieseltraction,(Fig.18.12),theforcedevelopedbythetractionenginedecreaseswithincreasingspeed,whilethemaximumtractionforceZisdevelopedwhenthetrainstartstomove.Asspeedincreases,thetractionforcedecreases,atfirstlinearly(segmentAB)andasspeedincreasesfurther,resistanceplummets(segmentBC)levelingoffataminimum,correspondingtothemaximumspeedofthetractivevehicle.

Electrictrains,(Fig.18.13),cansustainmomentaryoverloads,inwhichcasethetractionforceisgreaterthanthatincontinuousoperationandthereforehigherspeedsareattainable.

Figure18.14illustratesthediagramsofthespecifictractionforcezasafunctionoflongitudinalgradientinthecasesofpassengerandfreighttrains.Usualvaluesofthespecifictractionforceare10÷20kg/tforpassengertrainsand10÷30kg/tforfreighttrains.

Fig.18.14.Specifictractionforcezofatraininrelationtolongitudinalgradient

18.8.Adhesionforces

ThecontactbetweenwheelandrailoccursalonganellipticalsurfaceknownastheHertzellipse,(Fig.18.15,seealsosections7.7and10.6.1).AlongtheHertzellipse,adhesionforcesFadhappear,whicharenecessarytoensurecontinuousrotationofthewheel.ThisrequiresthattheadhesionforceFadhbeequaltoorgreaterthanthetractionforceZ,(Fig18.16).

Fig.18.15.TheadhesionforceFadh

TheadhesioncoefficientμisdefinedastheratioofthehorizontaladhesionforceFadhtotheverticalwheelloadQ:

Fig.18.16.TractionforceZandadhesionforceFadh

Theadhesioncoefficientμdependsmainlyonweatherconditionsbutalsoontrainspeed,(Fig.18.17),(321).TosatisfytheconditionFadh≥Z,theminimumrequiredvaluesofμhavebeensurveyedandaregiveninTable18.3,(321).

Fig.18.17.Theadhesioncoefficientμinrelationtotrainspeedandclimaticconditions,(324)

Table18.3.Minimumrequiredvaluesfortheadhesioncoefficientμ,(321)

Concerningtheinfluenceofthevarioustrackandrollingstockcharacteristicsontheadhesioncoefficient,itwasfoundthat,(323),(331):•increasingwheeldiameterfrom700mmto920mm,causedlittleincreaseofadhesion,

•changingtheinclinationoftherailsonthesleepers,(seesection7.9,Fig.7.12),from1/40to1/20,decreasedadhesionby17%,

•increasingwheelloadfrom8tto12t,decreasedadhesionby12%.

Amedianvalueofμasarelationofspeedcanbeobtainedbytheformula,(320):

Finally,foramotorwheeltoperformproperly,thetheoreticalperipheralspeedofthewheelshouldbegreaterthantheactualtranslationalspeed,(Fig.18.18):

Fig.18.18.Speedsandforcesonawheel

where: ro :rollingradius

n :numberofrevolutions

Otherwise,therewillbe:braking,ifVrot<Vtrans,wheelskid,ifVtrans<Vrot≠0,wheellock,ifVrot=0>Vtrans≠0.

Itisevidentthatconstantorincreasingtrainspeedrequiresthatthetractionforcebeequaltoorgreaterthanthetotalresistancedevelopedduringtrainmotion.

18.9.Requiredtrainpower

Thetractionforcenecessaryfortrainmotionisensuredbytheenginepower,whichisdistinguishedbetweennominalpowerandeffectivepower.Nominalpoweristhepowerasspecifiedbytheenginemanufacturer.Auxiliarydevicesoftheengineabsorbapartofthenominalpowerandanotherpartislostduringtransmissionfromthemotorshafttothewheels.Theremainingpoweristermedeffectivepowerandisthepartactuallyavailabletopowerthemotorwheelsandthetrainasawhole.

Powerismeasuredineitherhorsepower(hp,ps,cv)orkilowatts(kW).Enginepower(inhorsepower)canbecalculatedbytheformula:

whereZisthetractionforceandPisthetrainweight.

Therefore,itisevidentthattrainpowerdependsonspeed,whichshouldbespecifiedeverytimethatapowervalueisgiven.Table18.4givesthepowerrequiredfortheoperationofvarioustypesoftrains.

Table18.4.

Powerrequiredbyvarioustypesoftrains,(324)

Poweroftenreferstounitweightofrollingstock,inwhichcaseitistermedspecificpowerNe(kW/torPs/t).Aparameter,whichdeterminesthecourseofatrain,isthedistancerequiredtoattainafinalspeed,(Fig.18.19).

Fig.18.19.RequireddistanceSasafunctionofspecificpowertoenabletrainspeedstartingfromzerotoreachafinalvalue

18.10.Valuesoftrainaccelerationanddeceleration

Thevaluesofaccelerationanddecelerationofatraindependonthetypeofrollingstock(passenger,freight)aswellasonthedistancewithinwhichthetrainmustattainitsmaximumspeed.Theshorterthisdistance,thehigherthevaluesofaccelerationanddeceleration,asisthecasewiththemetropolitanandsuburbanrailways.Forreasonspertainingtohumanphysiology,maximumaccelerationshouldnotexceed1.0m/sec2.

Typicalaccelerationvaluesforvarioustypesofrollingstockare:–freighttrains: 0.2÷0.4m/sec2,

–intercitytrains: 0.4÷0.6m/sec2,–suburbantrains: 0.6÷0.8m/sec2,–metros: 0.8÷1.0m/sec2.

Typicaldecelerationvaluesforvarioustypesofrollingstockare:conventionalfreighttrains: 0.10m/sec2,expressfreighttrains: 0.25m/sec2,passengertrains: 0.40÷0.50m/sec2,suburbanrailways,metros: 0.60m/sec2.

Acriticalparameterforpassengercomfortisthevariationofaccelerationperunittime,knownasjerk.Jerkshouldnotexceedthevalueof1.5m/sec2/sec.

18.11.Trainbraking

18.11.1.Brakingsystems

Twobrakingsystemsareinuse:(323),(325):–Shoe(orblock)brakes.Theyoperatewiththehelpofthefrictiondevelopedonthewheelsbythepressureofmetalorsyntheticshoes.Bothwheelsoftheaxlebeingbrakedareprovidedwithbrakingshoes.

–Discbrakes.Thebrakingactionisachievedbyfrictiononsteeldiscsorcastironfixedtotheaxle.Abasicdisadvantageofdiscbrakesisthegenerationofhightemperaturesreaching5000C,(319).Thefollowingmethodsareusedfortransmissionofthebrakingforce:

•Airbraking,usingchangesofairpressureinspecialconduits,initiatedinthedriver’scabbyoperatingavalve.Thissystemhasthedisadvantagethatbrakingisnotsimultaneousonalltrainvehicles.

•Electropneumaticbraking,developedinthe1960s,toreducethetransmissiondelayofthebrakingoperationtothevehiclesinatrain.Inthissystem,airpressureismodifiedsimultaneouslyatallwheelsbyelectricallyactuatedairvalvesateachbrake.Thesystemisoperatedbyanelectricsignaltransmittedonalinealongthetrain.

•Electromagneticbraking,developedinrecentdecadessoastoconfrontthegreatincreaseintrainspeeds.Inthistype,thebrakingactionisapplieddirectlytotherails.Specialshoeswithelectromagnets,whichcarryacurrentduring

braking,achievebraking.Electromagneticbrakingmayfunctionindependentlyorincombinationwithothersystems.

•Electrodynamicbraking,doingawaywithbrakeshoes’wear,sincedecelerationisobtainedbyconvertingtheelectrictractionmotorsintoelectricgenerators.Thepowergeneratedbybrakingisusedforauxiliarypurposes.Inthecaseofelectriclocomotives,theenergyrecoveredmaybereturnedtothepowernetwork,throughthepantograph.Therecoveredenergyis3÷6%inintercitytrains,20%inmasstransitandfreighttrainsand40%intrainsonhigh-gradienttracks,(320).

Railvehiclesareprovidedwithanti-skiddevices,whichmonitorwheelrotationandmodifythebrakingforcewheneverwheellockingisdetected.Inconsiderationoftrainbraking,specialconcernneedstobegiventopooradhesionconditionsthatcanbecreatedundercertainweatherconditionsduetorain,iceandleafdeposits.

Finiteelementanalysisgivesthepossibilityofstudyingbothmechanicalandthermodynamicalbehaviorofbrakingsystems(Fig.18.20).

Fig.18.20.Analysisofadiscbrakewiththeuseofthefiniteelementmethod

18.11.2.Brakingdistance

EmpiricalformulashavebeensuggestedtocalculatethebrakingdistanceLfor

thevarioustraincategories,(325).

Freighttrains(V<70km/h)ThebrakingdistancecanbecalculatedbyMaison’sformula:

where i:

trackgradient(‰orinmm/m).Trackgradientisregardedpositivedownhillandnegativeuphill,

φ:

frictioncoefficientdependingongradient.Valuesofφare:φ=0.10,fori<15‰

=0.10÷0.00133(i–15),fori>15‰ λ

:brakingpercentage,definedastheratioofthebrakingweighttototalvehicleweightandexpressingthebrakingforcerequiredforbrakingoneton.

Brakingpercentageλisacriticalfactorforthebrakingdistance.Table18.5givesvaluesofλforvarioustypesofrollingstockandbrakes.Inanycase,formula(18.28)givesthepossibilitytocalculatethebrakingpercentageλinrelationtothebrakingdistanceL,thetrainspeedV,thegradientiandthefrictioncoefficientφ.

Table18.5.Brakingpercentageλforvarioustypesofrollingstockandbrakes

Passengertrains(V=70÷140km/h)ThebrakingdistanceisgivenbythePedeluckempiricalformula:

withthevariousparametersdefinedasinformula(18.28).

Diesel-electricpassengervehiclesThebrakingdistanceisgivenbytheformula:

whereγisthedeceleration(m/sec2).

OtherempiricalformulasPreviousformulas,developedbytheFrenchrailways,arealsoinusebytheUIC,(329).However,theGermanrailwaysusetheso-calledMindenformulaforthebrakingdistance,whichis:

withtheparameterψtakingvaluesbetween0.5÷1.25(inrelationtothebraketypecharacteristics)whicharegivenbynomographs,(326).

Figure18.21illustratesthebrakingdistanceforlowandmediumspeedsandvariousrollingstocktypes.

Fig.18.21.BrakingdistanceLinrelationtospeed(atzerogradient)formediumandlowspeeds

Thebrakingdistancecalculatedbytheaboveformulasisaugmentedbyatleast10%asasafetymargin(dependingalsoonthesignalingsystem).Thegreaterthespeed,thelongerthebrakingdistance,(Table18.6).Figure18.22illustratesthebrakingdistanceathighspeeds.

Table18.6.Brakingdistanceinrelationtospeed

Fig.18.22.Requiredbrakingdistanceathighspeeds(trackwithzerogradient)

18.11.3.Europeanspecificationsconcerningbraking

AccordingtotheEuropeantechnicalspecificationsforinteroperabilityrelatingtorollingstockandconcerningbrakingoftrains,(333):–thetrainbrakingsystemshouldensurethatthetrain’sspeedcanbereducedormaintainedonagradient,orthatthetraincanbestoppedwithinthemaximumallowablebrakingdistance,

–theprimaryfactorsthatinfluencethebrakingperformanceare:thebrakingpower,thetrainmass,thetrainrunningresistance,thespeed,theavailableadhesion,

–themainfunctionalandsafetyrequirementsofbrakingsystemsinclude:•amainbrakefunctionusedduringoperationforserviceandemergencybraking,

•aparkingbrakefunctionusedwhenthetrainisparked,•themainbrakesystemmaybecontinuousorautomatic,•whenrunning,thedrivershouldbeabletocheckfromthedrivingpositionthefollowing:thestatusofthetrainbrakecontrolcommandline,thestatusofthetrainbrakeenergysupply,

•tocheckemergencybraking,testsshouldbecarriedoutondryrailsatthefollowingspeeds:30,60,80,120,140,160,200km/handatthemaximumdesignspeedofthespecificrollingstocktype.

19RollingStock

19.1.Componentsofarailvehicle

Everyrailvehicle(passengerorfreight)requiresasetofpartsanddevicesforitsmovement:wheels,axles,bogies,springs,couplingsandbuffers.

19.2.Wheels

19.2.1.Geometricalcharacteristicsandmaterials

Onstandardgaugetracks,thewheeldiameterofthehauledrollingstockrangesfrom0.84mto0.92m.Asthecontinuingtendencyistoincreasewheelload,onewouldexpectwheeldiametertoincreasealso.This,however,isnotfeasiblebeyondcurrentwheeldiameters,becauselargerwheelswouldontheonehandincreaseweightandthereforemanufacturingandoperatingcosts,andontheotherhandresultinagreatervehiclefloorheightfromtracklevel.Thiswouldbedetrimentaltoboththestabilityandthespaceavailableinthevehicle,sincetheloadinggaugeofthetrack(i.e.,thefreespacearoundtherollingstock)isfixedandcannotbechanged.

Fig.19.1.RunningsurfaceofawheelaccordingtotheUIC,(336)

Forstandardgaugetracks,thewheeldiameteroflocomotivesrangesbetween0.85÷1.10m,whereasformetricgaugetrackswheeldiameteraverages0.75m.Thediameterofrailcarsforstandardgaugetrackshasanaveragevalueof0.90m.Figure19.1illustratesthegeometricalcharacteristicsofawheelaccordingtotheUIC.

Fig.19.2.Tireandwheelrimofarailvehicle,(320)

Twomainpartscanbedistinguishedinawheel,(Fig.19.2):–thetire,whichistheexternalpartofthewheelandcomesincontactwiththerail.Sinceitissubjecttogreatwear,thetireismadeofamaterialhighlyresistanttowear,

–theinternaldiscofthewheel.Theexternalpartofthediscinsidethetireisthewheelrim.

Tirethicknessrangesbetween65÷70mm,andthetireisconsideredwornwhenwearreducesthethicknessto30mm.Thefirsttirematerialwassoftiron,butitworeoutquicklyandwasdifficulttoweldproperly.Accordingly,itwasreplacedbyhardsteel,which,however,shouldhavealowbrittleness.Inmetrovehicles,elasticwheelsaremoreandmorecommonlyused.

Fig.19.3.Detailsofgeometricalcharacteristicsofawheel,(333)

AccordingtotheEuropeantechnicalspecificationsforinteroperability,maximumandminimumvaluesforthegeometricalcharacteristicsofawheelaregiveninFigure19.3andTable19.1,(333).

Table19.1.Maximumandminimumvaluesofthevariousgeometricalcharacteristics

ofawheelaccordingtoEuropeanspecifications,(333)

19.2.2.Wheeldefectsandreprofiling

Wheelrimssufferfromanumberofdefectsdueto:thermalphenomena,theformofthewheelprofile,fatigueofthewheel-railcontact,andshelling(i.e.lossofmaterial),(337).Thefrequencywithwhichthesedefectsappearisdifferentinrelationtopredominanceofpassengerorfreighttraffic,asitcanbeobserved

whencomparingAmericanandEuropeanrailways.Theanalysisofstressesinthewheelhasrevealedmaximumvaluesinthe

rangeof2t/cm2÷3t/cm2,(334).Forthisreason,manyrailwayshaveset4t/cm2

asthelimitofwheelstress,(344).Duetowheelwear,areprofilingisnecessaryandisconductedinrelationto

wearandtraffic,usuallyevery100,000÷250,000kmoftraffic,(344).

19.2.3.Lifecycleofawheel

Thelifecycleofawheelmaybeshortinthecaseofatramway(250,000kmoftraffic)orhighinthecaseofahighspeedtrain(2,000,000km),(Fig.19.4),andisstronglyaffectedbythenatureoftraffic(passengerorfreight)andthevalueoftheaxleload.

Fig19.4.Lifecycleofwheelsinrelationtothetypeoftraffic,(337)

19.3.Axles

Wheelsareconnectedinpairsonaxles,forwhicheachvehicleincludesatleasttwo.Theincreasesinvehicleweight,combinedwiththeneedtokeepthestressesofthetrackwithinreasonablelimits,haveledtotheadditionofathirdandthenafourthaxle.

Fig.19.5.Wheel-baseofavehicle

Thedistanceδbetweenthetwomostdistantfixedaxlesofavehicleistermedthewheel-baseδofthevehicle(Fig.19.5).Thegreaterthewheel-baseofavehicle,themorestableitisonstraighttrackbutthemoredifficultitwillbetorunoncurvedtrack.Themaximumwheel-baselengthδenablingarailvehicletooperateindepotswithacurveofradiusRisgivenbytheformula:

Fig.19.6.Partsofanaxle

Anaxleiscomposedofthefollowingparts,(Fig.19.6):theaxle-journalJ,whichissupportedbythebearing,thewedgingregionB,whichisthepartoftheaxlewedgedintothewheelbody,themainbodyAoftheaxle,locatedbetweenthetwowheels.

Thevehicleloadisappliedtothebearingsandthencetransmittedtothejournalsandthewheels.Therearetwokindsofbearings,journalbearingsandrolling-contactbearings,whichareinturndistinguishableintoballbearingsandrollerbearings,(342).

Fig.19.7.Detailsofgeometricalcharacteristicsofanaxle

Stressesindrivingaxlesarebothtorsionalandbending,whilestressesintrailingaxlesareonlybending.

AccordingtotheEuropeantechnicalspecificationsforinteroperability,minimumandmaximumvaluesofthegeometricalcharacteristicsofanaxle,inrelationtowheeldiameter,aregiveninFig.19.7andTable19.2.

Table19.2.Maximumandminimumvaluesofgeometricalcharacteristicsofanaxle

accordingtoEuropeanspecifications,(333)

19.4.Bogies

19.4.1.Definitionandfunctionsofabogie

Fig.19.8.Bogie

Fig.19.9.Conventionaltypeofbogiesandlocationofsprings

Fig.19.10.Primaryandsecondarysuspensionofarailvehicle

Theincreaseinthenumberofaxlesofrailwayvehiclesgaverisetotheneedtoseparatetheaxlesintogroups.Thisisachievedbymeansofbogies,wheretwoormoreaxlesaremountedonthesameframe,(Fig.19.8).Incommonlyusedbogies,(Fig.19.9),theaxlebodyandthewheelsarerigidlyjoined,andasaresulttheyrotateatthesameangularspeed.Thebogieframesareconnectedtotherailvehiclebodyandtotheaxlesthroughspringsandshockabsorbers,providingthevehiclewithprimaryandsecondarysuspension,(Fig.19.10).

Bogiesperformthefollowingfunctions,(341):–supportrailvehiclebodyfirmly,–runstablyonbothstraightandcurvedtrack,–ensuregoodridecomfortbyabsorbingvibrationsgeneratedbytrackdefects,andbyminimizingtheimpactofcentrifugalforces,whenatrainrunsoncurves.

19.4.2.Formsofbogies

Bogiesareclassifiedintotwo-axle,three-axle,etc.,basedonthenumberofaxles.Thetwo-axlebogieisthemostcommon.

Anotherclassificationofbogiesisintoarticulatedandnon-articulatedtypes,(Fig.19.11).Twonon-articulatedbogiesusuallysupportonerailvehiclebody,whereasonearticulatedbogiesupportsthebackendoftheforwardvehicleandthefrontendoftherearvehicle.Althoughthearticulatedbogiehassomedisadvantages,suchasacomplexstructure,increasedaxleload(duetothesupportofonebodybyonebogie)anddifficultmaintenance,itoffersmanyadvantages,includingalowercenterofgravity,betterridecomfort(sincevehicleendsdonotoverhangbogies)andlesseffectofrunningnoiseonthepassenger,asseatsarenotoverbogies.

Fig.19.11.Non-articulatedandarticulatedbogie

19.4.3.Componentsofabogie

Thebasiccomponentsofabogieare:–therotatingbeam,whichallowsthebogietorotatetothevehiclebodyoncurves,isolatesthebodyfromvibrationsgeneratedbythebogie,andtransmitstractionforcesfromthebogietothebody,

–thebogieframe,whichaccommodatesvariousbogieequipmentandisgenerallyfabricatedbyweldingtogethertwosidebeamsandtwocrossbeamsintoanH-shapedframe.Thethicknessofthesebeamswasinitially6mm,thenincreasedto9mmandlateronto12mm,butitwasfinalizedat8÷9mm,inordertoreduceweight,(341),

–suspensiondevices,whichaffectperformanceofthebogieandcomfortofpassengers,

–transmissiondevices,whichconsistofgearandflexiblecouplingstotransmitmotivepowergeneratedbythemotorortheenginetotheaxle.

19.4.4.Self-steeringbogie

Fig.19.12.Self-steeringbogie

Whenatrainrunsonacurveathighspeeds,thewheelsexerthighlateralforcesontherailsandcausewearandtearofwheelflanges.Thislateralforcecanbereducedtoonehalforonethirdwiththeuseofself-steeringbogies,(Fig.19.12),whichallowthewheelsandaxlestomovemorefreely,andthustheaxlecenterlineisalignedontheradiusofcurvature,(343).

19.5.Springs

Springsareusedbetweenpartsofthesamerailvehicleaswellasbetweensuccessivevehicles.

IfPistheloadappliedonaspringandΔlisitslengthvariation,theworkenergystoredis:

Dependingonthetypeofrailvehiclethatthespringsareplacedon,constraintsaresettothemaximumvalueΔlasfollows:•locomotives,Δl:10÷15mm,•passengervehicles,Δl:50÷70mm,•freightvehicles,Δl:15÷25mm.

19.6.Couplingsandbuffers

Couplingsandbuffersaredevicesusedtointerconnectrailvehiclestoformtrains.Theirmainpurposeistotransferhorizontalforcesfromonevehicletothe

other.Forpassengercomfortreasons,springsinpassengervehiclecouplingshavea

lowvalueofΔlrangingbetween12÷20mm.Contrariwise,infreightvehiclecouplings,Δlisrangingbetween30÷50mm.

Asopposedtocouplingsprings,bufferspringsinpassengervehiclesshouldhaveahighvalueofΔl(rangingbetween50÷70mm),toabsorbthevariousshocksandvibrationsthoroughlyandquickly.Asimilarrequirementisnotnecessaryforfreightvehicles,inwhichΔlrangesbetween30÷50mm.

Hookcouplingswereformerlyusedtoconnectthevehiclesinatrain.However,automaticcouplingsareimplementedtoday,ensuringautomaticallythecouplingofsuccessiverailvehicles,inparticulartheconnectionofbrakeairpipesandelectricalcircuits,(340).

Buffersareemployedtokeepconstantspacingbetweenrailvehiclesandtoabsorbshocks.Instandardgaugetracks,bufferheightaboveraillevelis0.90÷1.25m.

AccordingtotheEuropeantechnicalspecificationsforinteroperability,(333):•thelevelofthecenterlineofbuffersshouldbe0.98÷1.065maboveraillevelinallloadingandwearconditions,

•thestandardscrewcouplingsystembetweenvehiclesshouldbenon-continuousandcompriseascrewcouplingpermanentlyattachedtothehook,adrawhook,andabarwithanelasticsystem,

•theheightofthecenterlineofthedrawhookshouldbe0.95÷1.045maboveraillevel.

19.7.Designofrollingstock

Designofrollingstockisafieldofcooperationbetweenthehumanitiesandengineeringsciences.Thetimespentbyapassengerinatrainshouldbeconsideredasamomentofhislifebyrespectingtheindividualityandpersonalityofeachpassengerandwiththeconcerntogivehimthepossibilityofenjoyingtraveltimebyrelaxing,workingordoinganythingelse.

Thedesignofeachtypeofrollingstockshouldbeanalyzedinrelationtothespecificcharacteristicsoftraffic(intercity,regional,suburban,etc.),traveltime,leveloftechnology,culturalattitudes(habits)ofclients,costofpurchaseandmaintenance.Agooddesignshouldensurethefollowing:safety,security,spaceandcomfort,modularityofthespace,calmness,alownoiselevel,lightingin

relationtoneeds,easyaccess(particularlyforthedisabledandtheelderly),andaviewtotheexternalphysicalenvironment,(335).

Fig.19.13.ErgonomyofseatsofsecondclassofthehighspeedParis-Lyonstrain

Ergonomy,therequiredspaceandadaptationoftechnologytohumanneeds,arekeyfactorsforagooddesign.Figure19.13illustratesthegeometricalcharacteristicsofaseatfromtheParis-Lyonshighspeedtrain.Thewholeanalysiscanbeconductedwiththeuseofthefiniteelementmethod.

Untilsomeyearsago,theonlyprioritiesindesignweretechnologyandeconomy.Thishaschanged,asaesthetics,decoration,andamorehumanenvironmentmakepartofagooddesign,whichmustemergeanewconceptionofhumanvalues,ofinnovationandofvalorizingthetraveltime.

Thereisatremendousvarietyoftypesofrollingstockforpassengerandfreighttraffic.Table19.3(nextpage)illustratescharacteristicsofsomehighspeedtrains.

Thereadercanlookfortechnicaldetailsinthewebsitesofconstructors,whicharewww.transportation.siemens.comforSiemens,www.transport.alstom.comforAlstom(whichabsorbedFiatFerroviaria),www.bombardier.comforBombardier(whichabsorbedABB).

Table19.3.Technicalandoperationalcharacteristicsofsometypesofhighspeedrolling

stock,(compiledfromdataofconstructors)

19.8.LocalizationofthepositionofarailvehiclewiththeuseofGPS

Asexplainedinsection1.14,localizationoftheaccurateposition(coordinatesx,y)atanymoment(t)ofarailvehicleandofitsspeed(V)maybedonewiththeuseofGPS(GlobalPositioningSystem)andGSM(GlobalSystemforMobileCommunications)applications.InformationonthepositionandspeedofthetrainistransmittedfromthesatellitestothetrainandnexttotheOperatingcontrolcenter(seesection20.10.4),andiscomparedautomaticallytowhathasbeenplanned.Anydifferencedetectedistransmittedautomaticallyandthecourseofthetrainisrescheduled.Suchsystemsareinusenotonlyforhighspeedtrains(forinstancethesystemnamedLocalysforThalystrains),butalsoforlow-trafficlines,suchastheEuropeansystemnamedLocoprol(Lowcostsatellitesignalingandtrainprotectionforlowdensitytrafficrailwaylines).

19.9.Tiltingtrains

19.9.1.Needswhichgaverisetothetiltingtechnology

Manyoftoday’srailwaylineswerebuiltmorethanonecenturyago,atwhichtimethetechnologyandtransportrequirementsrecommendedspeedswhich,by

today’sstandards,areconsideredlow.Asaresult,thetracklayoutofmanyrailwaylinesfeaturescurveswithasmallradius,particularlyinmountainousareas.

Duringthepastsixdecades,railwayshavetriedtoadapttomarketrequirementsbyimprovingthebasictrackcomponents(rails,sleepersandballast),inthemajorityofcases,however,withoutaddressingtheproblemofsmallradiuscurvatures.Thereweresomeexceptionsinthisrespectthough.Forinstance,insomepartsoftheworldnewdedicatedhighspeedlineshavebeenconstructed,andimprovementsweremadetothetracklayoutofsomeexistinglines.Despitetheseefforts,however,themajorityofrailwaylinescurrentlystillfeaturealmostthesamelayoutaswhentheywerefirstconstructed.Thus,inmostcases,railwaysmustreducetraveltimeswithoutnecessitating,forcostreasons,theconstructionofnewlinesortheimprovementofthelayoutoftheexistingones.

Tiltingtrainscouldofferalow-costsolutioninthisrespect,astheycanbeoperatedonexistingtracksandattainhigherspeeds(ascomparedtoconventionaltrains),thankstoamechanismwhichtiltsthevehiclebodyofthetrainwhennegotiatingcurves,thusgivingitanadditionalsuperelevation.Tiltingtraintechnology,undertherightcircumstances,offersanadequatealternativetohigh-costlayoutimprovement.

Nevertheless,thetiltingtrainsolutionshouldalwaysbecarefullyexaminedineachcase;itshouldbeexaminedwhether,(332),(338):

thereductionsintraveltimesaresufficient(takingintoaccountwhatothertransportmodes,suchasairplane,privatecarandbus,canoffer),anyimprovementstothetrack,thesignalingandpowersupplysystemswillberequired,thereturnofinvestmentwillbesatisfactory,thecostofoperationwillbecompetitive,ascomparedtothatofothertransportmodes.

19.9.2.Tiltingtechnology

Tiltingtrainstry(andoftenfullysucceed)toreducecantdeficiency(seesection14.2.2)incurvesbytiltingthevehiclebodyinrelationtothewheel-base,(seesection14.2.3,Fig.14.4).Therearetwodifferenttiltingtechnologies,(339):–thepassivemethod:wherebythevehiclesuspensionincreaseswhennegotiatingcurves,sothattheturningpointofthevehicleremainsaboveitscenterofmass.Thismethod,whichisappliedbytheSpanishTalgo,permitsa

tiltingangleof3°to5°betweenbodyandaxles,–theactivemethod:wherebyalargertiltingangle,upto8°,isachieved,whichiscalculatedasafunctionofthenon-compensatedcentrifugalacceleration.Whenthetrainentersatransitioncurve,thetransverseaccelerationsdevelopedatthebogiearedetectedbyaccelerometers.Instructionstobeginrotationofthevehiclebodyarounditsaxisaretransmittedbyanelectronicdevicelocatedatthefrontofthetrain.ThistechniqueisappliedbytheItalianPendolinoandETR,theSwedishX2000andtheGermanVT610.

Twomethodsofdetectionofcurvestoberunhavebeendeveloped,(339):anon-boardsystemforcurvedetection:wherebybogie-mountedaccelerometersdetectthetransverseaccelerationsofthebogie.Acurvedetectionsystem,calledagyroscope,whichisplacedatthefrontofthetrain,detectswhenthetrainisenteringatransitioncurve.Subsequently,ittransmitsanelectronicsignal,thusinitiatingtiltingofthevehiclebody(inrelationtotheaccelerationdetected).ThetechniqueisusedbythetiltingsystemsincontinentalEurope,anelectromagneticsystemforcurvedetection:wherebyin-trackdevicestransmitdataconcerningthetracklayoutcharacteristicstoacomputerlocatedonthetrain,sothat,attheappropriatetime,tiltingofthevehiclebodyisinitiated.Thistechnique,whichisappliedinJapanandformerlyalsobytheAPTtrainsinEngland,couldberegardedasmoreefficientthanthepreviousone,buthasthedisadvantagethatitrequiresin-trackdetectiondevices.

19.9.3.Technicalandoperationalcharacteristicsoftiltingtrains

Themaintechnicalcharacteristicsoftiltingtrainsareasfollows,(339):

AngleoftiltingThetrainsfeaturingapassivetiltingsystem(Talgo)achieveanangleoftiltingof3°to5°,whereasthetrainsfeaturinganactivetiltingsystemachieveanglesoftiltingupto8°.

MaximumspeedAllelectrictiltingtrainshavehighperformancewithrespecttospeed,rangingfrom200to250km/h.Thedieseltiltingtrainsfeatureamaximumspeedof160km/handareprimarilyusedforsuburbanservices.

RelationshipofspeedVmaxandradiusofcurvatureR

TherelationshipofspeedVmaxtoradiusofcurvatureRdependsonthevaluesofcantandcantdeficiency.Forconventionalrollingstock,therelationshipbetweenVmaxandR(m)isgenerally:

Fortiltingtrains,thisrelationshipbecomes:

i.e.anincreaseinspeedupto20%÷25%isachievedbytiltingtrainsincurves,ascomparedtoconventionaltrains.

AdditionalsuperelevationTheincreaseinspeedresultsfromtheadditionalsuperelevationinducedbythetiltingsystem,whichrangesfrom150÷200mm.

MechanismoftiltingThreedifferentkindsoftiltingmechanismhavebeendeveloped:pneumatic,hydraulicandelectric.Inordertoreducetheforcesexertedontherail,thetechniqueofself-steeringradialbogiesisapplied,(339).

AxleloadAlltiltingtrainshavealowaxleload,rangingbetween13÷17tn,incontrasttoconventionalpassengertrains.

TrackgaugeandgeometricalcharacteristicsofvehiclesTiltingtrainsfeatureahighadaptabilitytothedifferenttrackgauges(1.435m,1.524m,1.067m,1.000m)andgeometricalrequirementsoftherollingstock.

SignalingGenerally,theuseoftiltingtechnologyisaccompaniedbyanincreaseofthemaximumspeedoftiltingrollingstockinstraighttrack(comparedtoconventionaltrains).Thisresultsinanincreaseofbrakingdistances,thusrequiringcertainchangeswithrespecttosignaling.

PowersupplyThepowersupplysystemalsorequirescertainadaptations,theextentofwhichdependsonthespecificrequirementsoftherailwayandcountryconcerned.

Loadinggauge

Tiltingtechnologyrollingstockhasbeendesignedsothattheloadinggaugeissufficienttoallowfortheadditionalsuperelevation,whichisachievedincurves.Thus,noproblemsarisewhentiltingtrainsrunintunnels.

TrackcharacteristicsanddefectsAhighqualityoftrack(railUIC60,concretesleepers,ballastwithaminimumthicknessof35cmandahighhardness)isrequiredfortheoperationoftiltingtrains.Ifthemaximumspeeddoesnotexceed160km/h,timbersleeperedtrackisadequate.

Trackdefectsandfrequencyoftrackmaintenancearealmostsimilartothatoftracksrunbyconventionaltrains.

19.9.4.Reductionsintraveltimesbytiltingtrains

Tiltingtrainshaveachievedareductionintraveltimesbetween12%and33%,(338).

However,whentheapplicationoftiltingtrainsisnotaccompaniedbyanincreaseinspeedinstraighttrack(comparedtoconventionalrollingstock),thereductionintraveltimes(onlyasaresultofhigherspeedsincurves)rangesfrom12%to20%,withameanvalueof15%.Thismustbeconsideredasbeingthedirecteffectoftilting,sinceconventionalhighspeedtrainscanalsoachieveanincreaseinspeedonstraighttrack.

19.9.5.Costoftiltingtrains

ThecostoftiltingrollingstockconstructedinItalyisreportedtobe3÷5%highercomparedtoconventionalrollingstock.However,FrenchplansforatiltingTGVreporthighercostdifferences,ontheorderof10÷20%.

AccordingtostudiesconductedbytheFrenchrailways,areductionintraveltimeof1minuteachievedbytiltingtrainscostsbetween1.5÷4.5million€forspeedsupto160km/handbetween9÷18million€forspeedshigherthan160km/h,ascomparedtoacostof35÷40million€fornon-tiltingTGVtrains.Theadditionalcostsforrunningtiltingtrainsresultfromthehighercostsoftiltingrollingstockandfromadditionalcostsintrackandsignaling.

20DieselandElectricTraction

20.1.Thevarioustractionsystems

Therailwayvehiclewhichprovidesthenecessarytractionpowerforthemovementofatrainisoftenreferredtoasalocomotive.Tractionpowermayusesteam,dieselorelectricpower.

Thefirstpowergenerationsystemusedfortractionwassteam.Indeed,thespreadoftherailwayswasprimarilyduetotheindustrialrevolutionofsteam.Thefirststeamvehicleappearedin1804andwasusedforrailwaytractioninthe1830s.Formorethan120years,thesteamenginewastheprincipaltractionmodeforrailways.

20.2.Steamtraction

20.2.1.Operatingprincipleofthesteamengine

Steamengineoperationisbasedonthefollowingprinciple,(Fig.20.1).ThewheelTisconnectedtotherodMDbythecrankTM.TherodMDisconnectedtothepistonrodDEofthesteamcylinder,therebyconvertingthereciprocatingmotionoftherodDE,generatedbysteampower,intowheelrotation.Thewheelsofthemotoraxle,connectedtotherods(oneoneachside),areknownasthemaindrivingwheels.Asingledrivingaxleisnotsufficienttoprovidetherequiredtractionforceandthereforeotherdrivingaxlesarealsoprovided.Sincethelatter,however,cannotbedirectlyconnectedtotherod,theirwheelsarecoupledtothemaindrivingwheelsbyrodscalledcouplingrodswhich,inturn,aresuccessivelyconnectedtothewheelcranksTM,T1M1,etc.Theseaxlesareknownascoupledaxles.Thecoupledaxlesandtheaxlesofthemaindrivingwheelsarethedrivingaxles.Thetotalnumberofcoupledaxlesseldomexceedsfiveoratmostsix,butisneverlessthantwo.

Fig.20.1.Operationalprincipleofthesteamengine

Asteamlocomotivemayusecoalorpetroleumasfuel.Accordingtotheaforementionedoperatingprinciple,thethermalenergyliberatedbyeithercoalorpetroleumisstoredassteampressuredynamicenergyandisconverted,whennecessary,totrainkineticenergy.

20.2.2.Mainpartsofasteamlocomotive

Themainpartsofasteamlocomotiveare:•thevehicle,mainlycomprisingtherollingdevices,theframe,thecouplingdevices,buffers,suspension,etc.,aswellasthedriver’scab,inwhichallequipmentandinstrumentsforlocomotiveoperationandcontrolandforrunningthetrainasawholearelocated,

•steamgenerationequipment,i.e.theboilerandassociatedpartssuchaswaterpump,etc.,

•theengine,i.e.steamcylinders,pistons,slidevalves,distributiondevices,•variousauxiliarysystems,e.g.aircompressorsforbraking,centralheating,sandboxestoincreaseadhesionbetweendrivingwheelsandrails,lubricationandbrakingdevices,severalsafetysystems,etc.

20.2.3.Disadvantagesandabandonmentofthesteamlocomotive

Presently,steamtractioniscommerciallyemployedonlyoncertainrailwaylinesinAfricaandAsia,whereasinEuropeandNorthernAmericaithasbeenamuseumitemforquiteafewdecades.Therearemanyreasonsthatsteamlocomotivesarenolongerused,(324):lowfuelefficiency.Onlyabout6%oftheenergyliberatedbycoalcombustionisusedfortraintraction,

poortechnicalperformance.Steamlocomotivescannotexceedapowerof3,000Hpandamaximumoperatingspeedof120÷140km/h,theneedtomaintainalargenumberofwatersupplyfacilities,highmaintenancecost,time-consumingfuelreplenishmentprocedure.Asteamlocomotivecanoperateautonomouslyonly12÷14hours,increasedfirehazard,harmtotheenvironment(atmosphericpollution,noise).

20.3.Fromsteamtractiontodieseltractionandelectrictraction

20.3.1.Fromsteamtractiontodieseltraction

Dieseltractionoftrainswasintroducedduringthe1930sbutwassystematicallydevelopedduringthe1940sand1950s.Diesellocomotivesaredrivenbyadieselinternal-combustionengine.Incomparisontosteamtraction,dieseltractionoffersfarhigherefficiency,aloweroperatingcost(byatleast50%),muchbetterperformance(power,speed),cleaneroperation,improvedpassengercomfort,convenience,andlessstrenuousworkforthedriver.

20.3.2.Fromsteamtractiontoelectrictraction

Theemergenceofelectricrailwaytractiondatesbackto1879.Thefirstimplementationofelectricpowerinrailwayvehicleswasrestrictedtourbanareas,withthedevelopmentoftheelectrictramwaysbetween1880÷1914andthefirstmetrolines.

Electrictractionwasfirstintroducedinrailwaysin1900,whenitwasadoptedintheLondonandParismetrolinesandinthemountainousrailwaylinesofSwitzerland.

Since1920,electrictractionhasbeenusedextensively,especiallyafter1950.Itsoperatingcostisalmosthalfcomparedtothecostofdieseltraction,butitnecessitatesahigherinitialexpenseduetothefixedinstallations(contactwires,pantographs,substations,etc.)required(seesections20.5.1and20.8.1).Electrictractionisaccordinglyusedonlyonhigh-trafficlines.

20.3.3.Gasturbinelocomotives

Gasturbinelocomotivesweredevelopedinthe1960sandearly1970s.Thebasic

elementofagasturbinelocomotiveisthegasturbineengine,operatingbytheexpansionofoverheatedandcompressedgaseouscombustionproducts.Aftertheenergycrisisof1973,gasturbineswerenolongercost-efficient,duetotheirhighenergyconsumption,andtheyhavebeenabandoned.

20.4.Dieseltraction

20.4.1.Operatingprincipleofthedieselengine

Fig.20.2.Schematicrepresentationofdieselengine

Thebasicelementofthedieselengine,(Fig.20.2),isthecylinderC,insidewhichthepistonPmovesbyreciprocatingmotion.ThisreciprocatingmotionistransmittedasrotarymotionbytherodPKandthecrankOKtothemaindrivingcrankshaftO.OnthecylindercoverarelocatedthevalvesAandB,permittingfunctionsinthefollowingorder:–suction,–compressionandinjectionofgaseousfuel,–combustionandexpansionofgaseouscombustionproducts,

–exhaust.

Athirdvalveisprovidedneartheothertwo,lettingincompressedairtostarttheengine.Allthreevalvesarespringloadedandareopenedandclosedatappropriatetimesbyleversandacamshaft.

Theaforementioneddescriptionreferstoasingleactionengineinwhichsuction,injectionandexhaustoccurinthecylinderonthesamesideofthepiston,specificallyontheupperside.

Themotorfunctionofadieselengineiscarriedoutinfourcycles,asfollows:1.Suctionstroke.Thisinvolvesthetimeperiodinwhichthepiston,startingfromtheupperdeadpoint(UDP),withvalveAopenandvalveBclosed,descendstothelowerdeadpoint(LDP),whilecylinderCisfilledwithfreshair.

2.Compressionstroke.ThiscorrespondstotheascentofthepistonfromtheLDP,whenvalveAandvalveBcloseandremainclosed,totheUDP.Thus,theairpressureinthecylinderincreasesfrom1atmosphereto30÷40atmospheres,causingthetemperaturetoreach400÷500°C.ShortlybeforethepistonreachestheUDP,fuelisinjectedunderpressureintothecylinder.ThefueldropletssubsequentlyigniteatthemomentwhenthepistonreachestheUDP.ThepressurewithinthecylinderCthenreaches50÷80atmospheresandthetemperaturereaches1,800÷3,0000C.

3.Expansionstroke.ThiscorrespondstoclosedvalvesandtoapistontravelfromUDPtoLDPundertheactionofexpandinggases.ValveBopensattheappropriatemoment.

4.Exhauststroke.ThiscoversthepistontravelfromLDPtoUDPwithvalveBopen.Combustiongasesareforcedout,whilealargepartofthegasesisreleasedfromthecylinderduringthefirstmomentsofthisstroke.ThepistonpushestheremainderduringitsascenttotheUDP,whenvalveAopens.

Uponcompletingtheabovecycle,thepistonreturnstoitsinitialpositionandtheprocessisrepeated.Itispossible,however,tocompletetheentirecycleintwostrokes,inwhichcasewehaveatwo-strokeengine.Withrespecttothenumberofcylinders,therearedieselmotorswith4,5or8in-linecylinders,or8÷12cylindersinaVarrangement.Motorspeedsrangefromlow(750r.p.m.)tohigh(1,200÷1,600r.p.m.).Low-speedmotorsareheavierforthesamepower.Inordertowithstandhightemperatures,cylindershavedoublewallsforwatercirculationinbetween.

20.4.2.Transmissionsystems

Indiesellocomotives,drivepowertransmissionfromthemotortothewheelsisachievedbythefollowingmethods:–byhydrodynamictransmissionandhydrodynamicspeedshifting(e.g.oftheVoithtype),

–byhydrodynamictransmissionandmechanicalspeedshifting(e.g.oftheMekydrotype),

–byelectricaltransmission,inwhichcasethedieselenginedrivesanelectricgeneratorinturndrivingaseriesofelectricmotors,whicharejoinedwiththeirdrivingwheelsthroughgearboxes.Inthecaseofanelectricaltransmission,nogearboxesareemployedandoperatingconditionsareidenticaltothoseinelectriclocomotives.Diesellocomotivesofthistype,termeddiesel-electriclocomotives,areessentiallydirectcurrentgeneratorsystemssupplyingthemotorsofthedrivingaxles.Iftractionrequirementsarehigh,severaldiesellocomotivesinseriesmaybeusedinthesametrain,

–byothermeans,e.g.byhydrostatictransmission,orbypurelymechanicaltransmission.

20.4.3.Requirementsofdiesellocomotives

Adiesellocomotiveshouldmeetthefollowingrequirements,(360):

•pullingcapabilityofmediumandheavyloadsonaleveltrack,uphill,ordownhill,withahightransmissionboxefficiencyatmediumandhighspeeds,

•overloadcapability,ontheonehandinthelow-speedrange,andontheotherhanduphillatfullload,

•capabilitytobrakewithnoslippageathighspeeds,aswellastokeepwithinspeedlimitsdownhillwithoutusingmechanicalbrakes,

•motoroperationwithinthefavorableoperatingregion,•highreliabilityandlowmaintenancecost.

20.4.4.Advantagesanddisadvantagesofdieseltraction

Dieseltraction,incomparisontoelectrictraction,requiresnoadditionalcostsfortrackequipmentandprovidesautonomy.

However,dieseltractionhasthefollowingdisadvantagescomparedtoelectrictraction:–lowerperformance(power,force,speed),

–higherenergyconsumption,–moreairpollutionandnoise,–highermaintenancecosts.

20.5.Electrictractionanditssubsystems

Incontrasttodieseltraction,wheretheenergyrequiredfortrainoperationisgeneratedwithinthediesellocomotiveitself,theenergyneededforelectrictractionistransmittedtotheelectriclocomotivebyanexternalsubsystem,thepowersupplysubsystem.

20.5.1.Powersupplysubsystem

Thepowersupplysubsystemincludes:–substations,wherethevoltageissteppeddownand(incertainelectrictractionsystems)thealternatingcurrent(AC)frequencyisconvertedortheACisrectifiedintodirectcurrent(DC),

–overheadcontactwiresorconductorrailstoconveytheelectricenergyfromthesubstationstotheelectriclocomotive.

Theelectricsubstationsmayobtainelectricpower:eitherfromthenationalhigh-voltagepowernetworkatafrequencyof50HzinEuropeor60HzintheUSAorfromaseparatehigh-voltagedistributionnetwork,atafrequencyof16⅔Hz,considerablylowerthanthatofthenationalnetwork.Thisseparatenetworkmaybeconnectedtothenationalnetworkormaybeindependent,i.e.itmayhaveitsownpowergeneratingplants.

Therefore,whenplanningtheelectrificationofarailwayline(existingorunderconstruction),theproximityofthenationalpowernetworktotherailwaylineaswellastheenergyavailablefromthepowernetworkshouldbeconsidered.

Insubstations,thecharacteristicsoftheelectricenergyobtainedfromthepowernetworkarechanged(voltagereductionand/orfrequencyconversionand/orrectificationfromACtoDC)andtheconvertedenergyischanneledthroughthetransmissionlinetotherailvehicles.Substationspacingrangesfrom15÷70kmandmainlydependsontheelectrictractionsystembutalsoonthelinetrafficload.

Asarule,thetransmissionlinefromsubstationstovehiclesisinsingle-

phaseconfiguration.Electrictractionenginesobtainelectricpowerfromaconductor,whichmaybe:–eitheranoverheadcontactwire,asusedinrailwaysand(sometimes)inmetros,

–oraconductorrail(oneortwo),usedinmetrosandinsomesuburbanrailways.

Whenonlyoneoverheadcontactwireorconductorrailisprovided,groundingofcurrentisdonethroughtherails.Eitheroneorbothrailsmaybeused.

20.5.2.Tractionsubsystem

Thetractionsubsystemincludestheelectrictractionenginewithallitsequipmentanddevices.Inthissubsystem,electricenergyisconvertedintomechanicalenergy,whichisusedtooperatethetrain.

Inthecaseofanoverheadcontactwire,electricpoweristransferredtothevehiclethroughapantograph.Inthecaseofthirdorfourthrailconductors,collectorshoesonthevehiclespickupthepower(seesection20.8.6).

20.5.3.Requirementsandpriorities

Thetwoaforementionedsubsystems,powersupplyandtraction,havedifferentrequirementsand,dependingonthepriorityassignedtoenergytransmission(powersupplysubsystem)orenergyuse(tractionsubsystem),variouselectricsystemshavebeendeveloped.

20.6.Electrictractionsystems

20.6.1.Directcurrenttraction

Directcurrenthasabetterperformancecomparedtoalternatingcurrentasregardsthetractionsubsystem.Foralongtime,therefore,fromthebeginningofthe20thcenturyuntilabout1950,prioritywasgiventogoodmotoroperation.Asseries-excitedDCmotorsofferedthebestoperatingconditionsforrailwaytractionuntilsomedecadesago,railwayengineerssoughtanelectrictractionsystemusingdirectcurrent.Earlyelectrictransmissionsystems,therefore,operatedatthesamevoltageasthetractionmotors.Themainvoltagesemployedwere:

–750V,mainlyfortransmissiononthirdandfourthrailsystems,–1,500V,morewidespreadthanothervoltages,–3,000V.

Theabovevoltagesarefarlowerthanthoseemployedonnationalpowernetworks(150,000V,220,000Vand280,000V)andtoolowforefficientpowertransmission.DCrailwaytractionthereforenecessitateslargecross-sectionsofthecontactwire(400÷900mm2)andcloselyspacedsubstations.Spacingofsubstationsis15÷20kminthecaseof1,500Vand35÷40kminthecaseof3,000V,(351).

AccordingtoUIC,directcurrenttractionsystemsforspeedsupto250km/hmustcomplywiththefollowingrequirements:standardheightofcontactwire:5.0÷5.5m(minimum:4.9m,maximum:6.2m),maximumpermissibleaveragecontactforcefor220km/h<V<250km/h:26kg,for200km/h<V<220km/h:22kg,for160km/h<V<200km/h:18kg,maximumspanlength65m,maximumlateraldeflectionofcontactwireatsupport≤30cm,(351).

Therefore,directcurrentrailwaytraction,thoughmoreefficientasregardsthetractionsubsystem,proveslessefficientwhenitcomestothepowersupplysubsystem.DCtractionispresentlyusedinabout36.8%ofelectricrailwaylinesworldwideandhasmainlybeenusedinFrance,Spain,Italy,Japan,certainpartsoftheU.K.,Russia,andIndia.

20.6.2.Alternatingcurrenttraction

Alternatingcurrenthasabetterperformancecomparedtodirectcurrentasregardsthepowersupplysubsystem,butencountersproblemsinthetractionsubsystem.ACmotorsmeetingtherequirementsoftractionenginesareseries-excitedACmotorswithacollector,which,however,faceproblemsrelatedtotheACfrequency.TheneedthereforeinitiallyarosetouseACatafrequencylowerthanthe50Hzusedatthenationalpowernetwork.

20.6.2.1.Alternatingcurrenttractionat15,000V,16⅔Hz

Inthissystem,electricsubstationsmayobtainpowerfromeitheroftwosources:–fromthenationalpowernetwork(atafrequencyof50Hzor60Hz),inwhichcasethereisvoltagereductionandfrequencyconversioninthesubstations,

–fromaseparatenetworkcarryinglow-frequencyAC,inwhichcasethereisonlyvoltagereductioninthesubstations.

ACtractionat15,000V,16⅔HzisusedinCentralEurope(Germany,Austria,Switzerland)wheresubstationsaresuppliedfromspeciallow-frequency

ACpowerplants,andinNorthernEurope(Sweden,Norway)wheresubstationsaresuppliedfromthe50Hznationalpowernetwork.However,since1996,thefrequencyof16⅔Hzwasincreasedby0.2%to16.7HzintracksofAustria,ofSwitzerlandandtheformerWestGermany.ACtraction15,000V,16⅔Hzcorrespondsto13.8%ofelectricrailwaylinesworldwide,(Fig.20.4),substationsarespaced20÷50kmapartandoverheadcontactwireshaveconsiderablysmallercross-sectionsthaninDCtraction.Thissystem,however,hasthedisadvantagesreferredtoinconnectionwithmotors,mainlytheirgreatsusceptibility.

20.6.2.2.Alternatingcurrenttractionat25,000V,50Hz

Toovercomethedisadvantagesofthetwopreviouslydescribedsystems,itwasnecessarytoseekatractionsystemthatcombinestheadvantagesofbothsystemswithoutpresentinganyoftheirdisadvantages.Thiswasachievedafter1950withthedevelopmentofefficientandlightweightignitronrectifiers,latersupersededbythyristors,whichintheirturnhavebeensupersededduringthe1980sbythe‘gateturnoff’technology,(seesection20.10.3).Inthissystem,substationsaresuppliedfromthenationalelectricnetworkandsimplystepthevoltagedownto25,000V,50Hz,whichistransmittedtothelocomotivethroughthecontactwire.Inthelocomotive,thevoltageisagainsteppeddown,rectified,andappliedtotheseries-excitedDCtractionmotors,(358).

The25,000V,50Hzsystemrepresents44.6%ofelectricrailwaylinesworldwideandisalmostexclusivelyusedinnewelectricrailwaytractionfacilities.Substationsarespacedatdistancesof50÷70kmandcontactwireshavecross-sections3÷5timessmallerthaninDCsystems.In2011,outof272,447kilometersofelectrifiedlinesworldwide,30.2%usedDC3kV,6.6%usedDC1.5kV,13.8%usedAC15KV,16⅔Hz,44.6%usedAC25kV,50Hzand4.8%usedotherelectrificationsystems,(1).

Acomparisonoftheconstructioncostfortractionsystemsusing1,500VDCandsystemsusing25,000V,50HzAC,yieldsfigureslowerby30%forthelatterthanfortheformer,(Fig.20.3),(356).

Figure20.4illustratesthetractionsystemsforthevariousEuropeancountriesandFigure20.5thebasiccomponentsandcharacteristicsofeachsystem.

In2011,outof178,418kilometersofelectrifiedlinesinEurope(RussianFederationincluded),35.4%usedDC3kV,5.2%usedDC1.5kV,19.6%usedAC15kV,16⅔Hz,37.4%usedAC25kV,50Hzand2.4%usedotherelectrificationsystems,(1).

Fig.20.3.ConstructioncostofDCandACtractionsystems(economicdataofWesternEurope),(356)

Fig.20.4.ElectrictractionsystemsinvariousEuropeancountries

Fig.20.5.Basiccomponentsandcharacteristicsofthevariouselectrictractionsystems,(360)

20.6.3.Advantagesanddisadvantagesofelectrictractioncomparedtodieseltraction

Abasicadvantageoftheelectriclocomotiveisitsspecificpower(50÷55kW/t),morethandoublethespecificpowerofthediesellocomotive(20÷25kW/t),(Fig.20.6),(347).

Electriclocomotivescansustainmomentaryoverloads(whenstarting,onsteepgradients,etc.),incontrasttodieselones,aslongasacceptablelifetimeandmaintenancecostconstraintsareconsidered.

Furthermore,alonglinescrossinghigh-altitudeareas,nopowerdropisobservedwithelectrictractionengines.Thisisnotthecasewithdieselengines,astheairenteringtheengineissignificantlyreduced.

Inthecaseoflongtunnels,electrictractionismandatoryduetothelimitedairsupply.

Finally,electricenginescauselittle,ifany,atmosphericpollution,whilemaintenanceisfarsimplerandeasierthanwithdiesellocomotives.Nevertheless,itshouldbenotedthatevendieseltrainspollutemuchlessthanautomobiles(attheratioof1:14perpassenger-km).

Fig.20.6.Comparativepowerofelectricanddiesellocomotives,(347)

20.7.Feasibilityanalysisbeforeelectrification

20.7.1.Feasibilityanalysisparametersandprocedure

Whenconductingafeasibilityanalysistojustifyelectrificationofarailwayline,twocostfactorsshouldbetakenintoconsideration:

•fixedinstallationscosts,includingoverheadcontactsystemsandsubstations,whichdonotdependontrafficvolume,

•operatingandmaintenancecosts,whichdependontrafficvolume.

Thequantitycommonlystudiedisthetotalannualcostsasafunctionoftheline’straffic,anindexofthelatterbeingtheenergyconsumedannuallyperkilometerofline.Figure20.7illustratesacomparativepresentationoftheannualcostsofdieselandelectrictraction.

Weseethatatlowtraffic,electrictractionisnotcost-effective.However,asthepointbeyondwhichelectrictractionbecomescost-effectiveisapproached,amoredetailedinvestigationoftheproblemisrequired.

Theperiodoffeasibilityanalysisusuallycovers20÷25years,andcostsasawhole(initialconstructioncostandannualoperatingcosts)areconvertedforeachtractionsystemtoconstantpricesbythepresentvaluemethod.Afeasibilityanalysisofelectrictractioninvolvesmanyuncertainties,particularlywithrespecttothepriceofliquidfuelinthenext20÷25years,theadjustmentinterestratewherebythevariouscostsareconvertedtoconstantprices,thelengthofthefeasibilityanalysisperiod,etc.Itisaccordinglyadvisabletoalsoperformasensitivityanalysis(whichaimstoexaminetheimpactofthevariationofoneparametertotheresultofthefeasibilityanalysis),(16).

Fig.20.7.Annualcostsasafunctionofenergyconsumptionperkilometeroflinefordieselandelectrictraction

20.7.2.Criterionforselectionofthelinestobeelectrified

Inmostcases,theneedarisestoreachaconclusioneasilyandquicklyastowhetherornotelectrificationofaparticularlineisadvisableandthenconductadetailedfeasibilitystudy.Thevariousrailwaynetworkshaveaccordinglyadoptedduringthe1970sand1980ssimplecriteriatothiseffect,themostwidelyusedbeingthenumberoftrainsonalineor(moreprecisely)theenergyconsumptionperkilometerofline.

Thecriteriainquestionvaryfromonerailwaytotheother,sincetheparticularitiesofeachcountryasregardscostoflabor,costofenergy,costofborrowing,etc.,areinvolved.

Acriterion,which,however,canonlybeusedtomakeafirstapproximateestimation,isthenumberoftrainsrunningontheline.Forexample,until1973(whenthecostofenergywaslow),alinehadtoberundailybyatleast30trainsperdirectiontoqualifyforconsiderationofelectrification.Aftertheenergycrisesof1973and1979,thecriterionbecamearound15trainsperdirectiondaily,andithaschangedeversinceinrelationtotheincreaseofcostofenergy.

However,giventhatatrainmaytransportpassengerorfreightwithavaryingnumberofvehicles,acriterionmaybetheenergyconsumptionperkilometerofline,whichforadoubletrackis1.0÷1.3MW/kmforahigh-speedlineand1.7÷2.5MW/kmforaheavy-freightline.Forinstance,theFrenchrailwaysconsiderinprincipleanannualconsumptionof70,000kW/kmoflineastheelectrificationcost-effectivenessthreshold,whiletheGermanrailwaysestimatethislimitat150,000kW/km,(355).Criteria,therefore,maydiffersignificantlyfromonerailwaytotheother.

Whenthetrafficloadortheenergyconsumptiononaparticularlineexceedstheabovelimits,adetailedfeasibilitystudyshouldbeconducted,asdescribedinsection20.7.1,beforeanydecisiontoelectrifythelineismade.

20.8.Overheadcontactsystem

20.8.1.Partsandcomponentsoftheoverheadcontactsystem

Theoverheadcontactsystemincludes,(354):Feederconductors,contactconductors(touchingthepantograph),suspension

wireropes,guywires.Conductorsupportstructures,whichmayconsistofpoles,(Fig.20.8),orframes,(Fig.20.9).Insulators,postbrackets,(Fig.20.10),tensioningdevices(usuallyevery1,200m),counterweights,variousmountinghardware,wiresconnectingthepolestothecontactwireandtotheground,andconductorsforconnectiontothesubstations.

AsillustratedinFigure20.10,theoverheadcontactsystemissuspendedfromthepostbrackets,whichinturnaremountedbyinsulatorsonsupportingpoles,erected3.25m÷3.80mfromthetrackaxis(thisdistanceisincreasedincurvesby40cmmaximum).Thepostbracketsareusuallyzinc-platedsteelpipes.

Fig.20.8.Pole-supportedoverheadcontactsystem

Fig.20.9.Frame-supportedoverheadcontactsystem

Fig.20.10.Insulatorsandpostbrackets(Cisthesupplypoint)

20.8.2.Calculationofthecharacteristicsofthecontactwirewiththeuseofphysicalmodels

Calculationofthecross-sectionandothercharacteristicsofthecontactwireisperformedonthebasisofthepermissiblevoltagedropfromthesubstationstothelocomotiveswitchboards,allowingafluctuationofnomorethan10%fromthenominalvalue.

Theoreticalcalculationofthevoltagedropisbasedontheassumptionthatthepassingloadisconstant,which,however,isnotthecase,sincethenumberoftheoperatingtrains,theirpositions,etc.arevariable.Calculationofthecharacteristicsofthecontactwirecanbeconductedeitherwiththeuseofthefiniteelementmethod(seebelowsection20.8.3)orwiththehelpofasmall-scalephysicalmodel,where:•substationsaresimulatedbyconstant-voltagesources,complementedbysuitableresistorssimulatingtheinternalcircuitsofthestations,

•currentfeederandreturnwiresaresimulatedbysuitableresistors,•trainsaresimulatedbyvariableresistors,whichcanbeconnectedtovariouspointsoftheline,

•suitablemeasuringinstrumentsgiveadirectreading(asafunctionofsubstationdistanceandtransmissionlinecross-section)ofsubstationoutputvoltage,totalcurrentateachsubstation,voltageatengineswitchboards,etc.

Thisphysicalmodelwasusedextensivelyuntilthe1980sandenabledthetestingandverificationofvariouscombinationsoftransmissionconductors,substationdistances,etc.andtheselectionoftheoptimumsolution.

20.8.3.Calculationofthecontactwirewiththeuseofthefiniteelementmethod

Thefiniteelementmethodcanbeusedfortheaccurateanddynamicanalysisofthebehaviorofthecontactwireanditcantakeintoaccountthefollowing:geometricalparametersoftheoverheadcontactsystem,conductorcharacteristics(cross-sections,materialsandtheirappropriateconstitutivelaw,etc.),pantograph’smass,thespringanddampercharacteristicsofthepantograph,numberandspacingofpantographs,andaerodynamiceffects,(350).Suchacalculationhasbeenconductedonthehigh-speedParis-Marseillelineandpermittedcalculationofthefollowing,(Fig.20.11):–contactforcebetweencontactwireandpantograph,–oscillationsofthepantograph,–positionofthetransmissionline.

Finiteelementanalysishasprovidedforthecontactwire(forAC25kV,50Hzandspeedsupto350km/h)thefollowingresults,(350):across-sectionof150mm2,aminimummechanicalresistanceof43kg/mm2,alinearmaximumresistanceof0.148Ohm/kmin20°C,

aconductivityof80%,amediumdeflectionofthecontactwireof6cmatthespeedof300km/hand9cmat350km/h.

Duringtheanalysis,thefollowingEuropeanstandards(orother,ifany)onoverheadcontactsystemsandpowersupplyshouldbetakenintoaccount:•EN50119,Overheadcontactsystem,•EN50149,Copperandcopper-alloycontactwires,•EN50163,Voltagesystemsonrailwaypower-supplynetworks.

Inanycase,accordingtoUICregulations,inthecaseof25,000V,50Hztraction,thecontactwirevoltage,inordertoensureanormaltractionenginepowersupply,shouldhaveamaximumvalueof27,500V,anormalvalueof25,000V,aminimumvalueof19,000Vandonlyamomentaryfallto17,000V,(348),(349).

Fig.20.11.Resultsofapplicationofthefiniteelementmethodforthecalculationoftheoverheadcontactsystemofahigh-speedtrack,(350)

20.8.4.Suspensionofoverheadcontactsystems

Varioussuspensionmethodsofoverheadcontactsystemsarebeingused,(Fig.20.12),dependingmainlyontrainspeed,butalsoonclimaticconditions(windspeedanddirection)andonpolespacing.Withlowspeeds(upto120km/h),simplesuspensionisadequate,whereaswithmediumandhighspeedscatenary-typesuspensionismandatory,(357),(358).

However,thecontactwireoscillatesatthetransverselevelwithamaximumdisplacementattheorderof20cm.Thus,aquickwearofthepartsofthepantographtouchingthecontactwireisavoided.

Fig.20.12.Suspensionmethodsofoverheadcontactsystems

Wheneverseveraltracksarelaidparallel(stations,tunnelentrance-exit,bridges,etc.),itisadvisabletoreconfigureandeliminatecertaintracksinordertoreducethetotalnumberoftrackstobeelectrified,(359).

20.8.5.Thepantograph

Thepantographtransferselectricpowerformtheoverheadcontactwiretotherailwayvehicle.AccordingtotheEuropeantechnicalspecificationsforinteroperability,(361):–theworkingrangeofapantographshouldbeatleast2,000mm,–thecontactpointofpantographtothecontactwireshouldbeataheight4,500÷6,500mmaboveraillevel,

–thestaticverticalforceexertedbythepantographheadonthecontactwireshouldbeattherange60÷90NforACsystems,90÷120NforDC3kVsystems,70÷140NforDC1.5kVsystems.

20.8.6.Powertransmissionbyconductorrail

Fig.20.13.Powersupplybyconductorrail

Asmentionedinsection20.5.1,electricpowermaybesuppliedtolocomotivesusingeitheranoverheadcontactsystemorconductorrails(oneortwo).Conductorrailsaremainlyusedinmetrosandsomesuburbanrailways.

Theconductorrailsolution,(Fig.20.13),ispreferableinthecaseofincreasedtrafficloads,forwhichverylargeoverheadlinecross-sectionswouldbeotherwisenecessary.Theconductorrailisequivalenttoanoverheadcontactsystemwitha900mm2cross-sectionandinthecaseoftunnelsallowsasmallerloadinggauge,andthereforeconsiderablesavings.

Inthevicinityoflevelcrossingsorturnouts,thethirdrailisinterruptedandspecialinsulatedcablesensurepowersupplycontinuity.Specialattentionshouldbepaidtosafety,possiblycoveringtheconductorrailwithinsulatingplatesatlevelcrossings,passages,andpersonnelworkingareas.Conductorrailsaremoresensitivetosnowandfrostthanoverheadsystems.Insomemetros(Londonundergroundforinstance)twoconductorrailsareusedtoavoidgroundingofcurrentontherunningrails.

Untiltheearly1950s,steelconductorrailswereextensivelyused,ironconductorslateron,andrecentlyaluminium-steelcompositerails.Permissibleintensityis2,800Aforanironconductorrailand4,700Aforanaluminiumcompositerailforamaximumtemperatureof85°C,acriticaltemperatureoftheenvironmentof40°Candaconductorcross-sectionof5,100mm2(specificationofthemetroofBerlin).

Becauseofthegreatmassoftheconductorrail,lengthvariationforextremetemperaturedifferences(-30°C÷+80°C)becomeshigh,andforthisreasonjointsareplacedevery45÷60m.

Conductorrailmaybeplacedattherailleveloroverthetrackgauge.

20.8.7.Electricalandpowercharacteristicsofsomehigh-speedtracks

Table20.1recapitulatestheprincipalelectricalandpowercharacteristicsofsomehigh-speedtracks.

Table20.1.Characteristicsofelectrificationofsomehigh-speedtracksinEurope,(346)

20.9.Overheadlinesupportingpoles

20.9.1.Polematerial

Thepolessupportingtheoverheadlinemayconsistofcaststeelorzincplatedsteelorprestressedconcreteorreinforcedconcrete.

20.9.2.Polespacing

Thespacingbetweensupportingpolesrangesbetween50÷75mdependingonthefollowingfactors:pantographoscillations,locomotivetransversemotions,climaticconditions.

Fig.20.14.Pantographoscillations

Figure20.14illustratesthetransversedisplacementDofthepantograph,resultingfromtheadditionof,(348),(359):–thehorizontaldefectHD,–thetransversedefectTD,whichisreflectedonpantographdisplacementmultipliedbytheratioμ:

–thetransversedisplacementLofthelocomotive,dependingonthespeedofthetrain,theheightoftheoverheadwire,thelocomotivesuspensionsprings,etc.

Bothlongitudinalandtransversepantographmotionhavetobecalculatedindetail.Itshouldbestressedthattheprimaryconstraintonmaximumtrainspeed(574.8km/hintestrunsin2001)isthemaximumpermissiblepantographoscillations,andtoalesserdegreethemetal-to-metal(wheel-rail)contact,(352).

20.9.3.Polefoundation

Whenerectingpolesforelectrictraction,specialcareisrequiredbothattheexcavationandatthefilling-upstages,(Fig.20.15),soastominimizeeventualsettlementoftheground.

Fig.20.15.Erectionofelectrictractionpoles

Whenthesubgradeisofgoodquality,foundationofthepoleshastheformillustratedinFigure20.16andcalculationofmomentsMisconductedaccordingtotheequation,(359):M=c·B·L3

withcoefficientcdependingonsoilcharacteristics.

Fig.20.16.Calculationofpolefoundationongood-qualitysubgrade

Inthecaseofpoorsubgrade,polesareerectedonaconcreteslabwiththeusualdimensions2.0m×3.5matadepthof1.1÷1.2m.

20.10.Substations

20.10.1.Substationsfeedingdirectcurrentsystems

SubstationsfeedingDCsystems,inadditiontosteppingthethree-phasevoltagedown,alsorectifytheACintoDC.

RectificationwasinitiallyperformedbyACmotor–DCgeneratorcouples,latersupersededbymercury-poolrectifiersandmorerecentlybysiliconrectifiers.

Fig.20.17.FunctionofaDCsubstation

Amodernsubstationincludesavoltagetransformerwithoneortwooutputvoltages,andarectifierassembly,(Fig.20.17).Silicondiodesorthyristorshavebeenusedasrectifiers,butsincethemid-1980s,theyhavebeenreplacedby‘gatetakeoff’technology(seebelowsection20.10.3).

20.10.2.Substationsfeedingalternatingcurrentsystems

InACsubstations,(Fig.20.18,nextpage),onlythevoltageisbeingsteppeddown,andthereforesubstationsinthiscasearesimplerthanDCsubstations.ACsubstationdesignshouldtakeintoparticularconsiderationtheriskofshort-circuiting,whichcanbepreventedbytheadditionofappropriatedevices.

Fig.20.18.ACsubstation25kV,50Hz

20.10.3.Fromthyristorsto‘gateturnoff’technology

Thyristorswereextensivelyuseduntilthemid-1980s.Theintroductionatthattimeofthe‘gateturnoff’technology,(Fig.20.19),permittedomissionofthecommutatingcircuits,thusenablingadistinctreductionofloadlosses,(Fig.20.20,nextpage).thyristortechnique‘gateturnoff’technique

Fig.20.19.Thyristorand‘gateturnoff’techniques

20.10.4.Operatingcontrolcenter

Nowadays,substationsandthesystemssuppliedbythemareremote-controlledandmonitoredfromanoperatingcontrolcenter,providedwithavisualpanelshowingthetracks,substationsandthesectionssupplied(andthereforecontrolled)byeachsubstation.Remotecontrolisachievedusingasignalcodecomposedofdifferentfrequencies.Electroniccontrolcircuitsinrecentyearshavemadepossibleexecutiontimesontheorderof0.3sec.

Fig.20.20.Loadlossesbythyristorand‘gateturnoff’techniques,(320)

20.10.5.Interferenceofelectrictractionwithtelecommunicationandsignalingsystems

Inadditiontopowertransmissionlines(inthecaseofelectrictraction),telecommunicationandsignalingcablesarealsorunning(usuallyunderground)alongsiderailwaytracks.Inordertopreventinterferencebetweenthepowerandtelecommunicationandsignalingcables,voltagesinducedinthetelecommunicationsandsignalingnetworkshouldbecalculatedprecisely.Installationsnearthetrackcomposedofsteelmayalsobeaffected.Themagneticfieldcreatedbythetrainequipmentusingcurrentmaybestrongandmayaffectneighboringtelevision,personalcomputersandhospitalequipment.Insuchcases,ariskanalysisshouldbeconducted.

Problemsmayalsoariseinareaswheretractionpowercablesintersectwithlinesofthepublicpowernetwork.

20.11.Synchronousandasynchronousmotors

Electricmotorsmaybeclassifiedintothefollowingthreegeneralcategories,(Fig.20.21,nextpage):Direct-currentmotors.Theinductorisfixed(stator)andcarriesDC.Inductiontakesplacebetweenthestatorandthemovingpartorrotor,whichissuppliedwithDCthroughbrushes,sothattherotorwindingscarryalternatingcurrent.MotorspeedisadjustedbyvaryingtheDCvoltageappliedtothemotoraswellasbyvaryingtheinducedmagneticfield.Thedirectionofrotationisreversedbyinvertingtheinductorconnections(polarityreversal).

Fig.20.21.Thethreecategoriesofelectrictractionmotors

Synchronousmotors.Theinductorisrotating(rotor)andcarriesDC.Induction

takesplacebetweentherotorandthefixedpart(thestator),whichcarriesthree-phaseAC.Rotationspeedisadjustedbyvaryingthefrequencyofthethree-phasealternatingcurrent.ReversingtheACphasesequencereversesthesenseofrotation.Asynchronousmotors.Theinductorisfixed(stator)andcarriesthree-phaseAC.Inductiontakesplacebetweenthestatorandtherotatingpart(rotor)whichcarriesthree-phaseAC.Speedisadjustedbyvaryingthethree-phaseACfrequency.Reversingtheinductorphasesequencereversesthesenseofrotation.

Asynchronousmotorsofferthefollowingadvantages:–lighterweight,abouthalfcomparedtosynchronousmotorsofthesamepower,

–higherefficiencyandtorqueandlesstrackloading,–simpleconstruction,reliabilityandsmallmaintenance.

Mostelectriclocomotivesusedirect-currentmotors.TheFrenchrailways,forinstance,employelectriclocomotivesoftheBBseries,manufacturedbyAlstom,weighing90tons,withapowerof4,400kWandaspeedof160km/h;theSwedishRailwaysuseR/C-serieslocomotivesmanufacturedbytheformerABB;theGermanrailwaysuseE181.2-serieslocomotivesmanufacturedbyKruppwithapowerof3,300kWandaspeedof160km/h.ExamplesofasynchronousmotorsaretheGermanhigh-speedICE,thehigh-speedEurostarLondon–Paris,whiletheFrenchhigh-speedTGVAtlantiquehassynchronousmotors.

Synchronousandasynchronousmotorsarepracticallyequivalentconcerningpower.Theyaremoreefficientthandirect-currentmotorsbecauseoftheirgreaterspeedofrotation.Asynchronoustechnologyisexpandingrapidly,inspiteofcomplicatedelectroniccommandsystems.Thechoicebetweensynchronousandasynchronousmotorsmustbebasedonananalysisofthepurchase,operationandmaintenancecostofeachoneofthem.

20.12.Electriclocomotivesmaintenance–Depot

Acriticalfactorforthegoodoperationoftherollingstockistheefficiencyandintimemaintenance.Maintenancemustbepreventiveandbasedonthefollowingprinciples:•specializationofstaffandequipment,•timelyschedulingofmaintenancesessions,

•appropriatemechanicalandcomputerequipmentfortheaccuratemonitoringofanydeficiencies,

•continuouscontrolandevaluationofresults,•reductionofcost.

Forelectrictractionengines,variousroutineinspectionsandmaintenancemustbeperformed:two-dayinspection,weeklyinspection,monthlytechnicalinspection,two-monthmaintenance,four-monthmaintenance,yearlymaintenance,generaloverhaulevery10years,generaloverhaulevery20years.Inordertooptimizetheuseofrollingstock,railwaysconducttheso-calledRAMS(Reliability,Availability,Maintainability,Safety)study(seealsosection16.11).

Maintenanceuptothefour-monthlevelcanbeperformedinthelocaldepot.Beyondthislevel,repairsareconductedatamaintenancefacility.

21Signaling—Safety—Interoperability

21.1.Functionsofsignaling

21.1.1.Evolutionofsignaling

Whenthefirsttrainsmadetheirappearance,itbecameclearthattrafficregulationandsafetyruleswerenecessary.

Aslongasrailwaylineswerefew,withasmallnumberofbranchesandcrossings,themainconcern(alsovalidtothisday)wastoensure,beforethedepartureofatrain,thatthelineaheadtothenextstopwasclear.Aseriesofaccidentsmadenecessarythepostingofguards,who,byhandorflagsignals,triedtonotifythetraindriveronwhetherheshouldstoporproceedalonghiscourse.

Unavoidablehumanerrorsbytheguards,however,ledtotheinstallationofsignalsvisibledayandnight(semaphoresignals),whichhadaclearermeaningtothedriverthantheflagsignalsusedbyguards.Foralongtime,semaphoresignalswerethebasisoftheregulationofrailwaytrafficandarestillemployedtoaconsiderableextent.Suchsignalsareusuallyilluminatedduringthenight.

Advancesinelectrictechnologyled,aroundtheendofthe19thcentury,totheemergenceoflightsignals,whichhavelargelysupplantedsemaphoresignaling.Lightsignalsarecurrentlytheprincipaltoolofregulationandsafetyforrailwaytraffic.

Untilthe1970stheregulationofrailwaytrafficwasdonewiththeuseoffixedlightsignalsalongthetrack.Asspeedincreases,however,theriskforthedrivertooverlookasignalalsoincreases.Athighspeeds,additionalsignalswithinthedrivercab(cabsignals)areaccordinglyemployed,providingcontinuousinformationontrafficandsafety,(368),(372),(374).Nowadays,cabsignalinghasbeenextendedtorailwaytrafficotherthanhigh-speed.

Duringthelastdecades,concernforsafetyresultedintechnologieswhichassureacontinuoustransmissionofinformationtothedriverandanautomaticcontrolwhetherthepermittedspeedandsignalscompliancehavebeenproperlyfollowed.CellulartelephonesandGSM(GlobalSystemforMobile

Communications)techniqueshavecontributedtosuchachievements.

21.1.2.Brakingdistanceandsignalingrequirements

Duetometal-to-metalcontact,railtransporthasalowrunningresistanceandthusalocomotiveiscapableofhaulingmuchgreaterloadsathigherspeedsthanaroadvehiclewiththesametractionpower.

Ontheotherhand,adhesionforcesbetweenwheelandrailarelowerthaninarubber-tiredroadvehicleandareattherootofaseriousdisadvantage:thedifficultyofstoppingamovingtrain.

Thebrakingdistanceis1,300÷1,400mataspeedof160km/h,2,500÷3,000mat200km/h,and7,500÷9,000mat320km/h,(374).Therefore,duetothelongbrakingdistances,theprotectionofthetrainfromobstaclesonthetrackcannotbelefttothevigilanceandquickreactionofthedriver.Earlywarningofthedriverisobligatoryandisachievedbysuitablesignalsandalarms.

21.1.3.Trafficsafetyandregularity

Therailwayisamasstransportationmediumandshouldensuremaximumsafetytopassengers.Threesafetyproblemsariseduringtrainmovement,(368),(372):–Protectionfromanothertrainmovingonthesametrackandinthesamedirection,eitherinfrontoforafterit.Duetothelongbrakingdistances,successivetrainsmustbeseparatedbylargesafetymargins,whichcanbenoshorterthanthebrakingdistance.

–Inthecaseofsingletracks,protectionfromtrainsmovingintheoppositedirectionandpreventionofahead-oncollision.Accordingly,themovementofatrainonanyparticularlengthoftrackisallowedonlyafterascertainingthatthetrackisandwillremainclear.

–Protectionfromtrainsmovingonanothertrackconverging(bycrossingorturnout)totheparticulartrack.

Theprimarypurposeofsignalingistrafficsafety.Atthesametime,however,itensurestrafficregularity,i.e.thepresenceofatrainataparticularpointataspecificmomentandatagivenpriority.Thus,thedegradationoftrafficregularitymayindirectlycauseareductionofsafety.

Onlineswithahightrafficload,whichapproachtrackcapacity(withtheriskofsaturation),signalingalsoaimsatincreasingtrafficcapacity,i.e.themaximumnumberoftrainsrunningontheparticulartrackperunittimeata

particularspeed.

21.1.4.Theregulatoryframework

Traintrafficisgovernedbydetailedrulesspecifiedinthescheduleservicemanualandinthegeneraltrafficregulation,withwhichthedriverisundertheobligationtocontinuouslycomply.Inadditiontoregulationprovisions,thecoursefollowedbythedrivershouldalsoconformtotheinstructionsgivenbystationdispatchers.

Onlineswithno(oroutoforder)lightsignaling,trafficregulationsadvisethedriverabouttheactiontobetakenineachcase.Evenonlineswithsignaling,however,trafficregulationsareimportanttotrafficsafety.

21.1.5.Basicsignalingfunctions

Signalingmustfulfillthefollowingfunctions:separationoftrainsmovinginthesamedirection,protectionoftrainspassingthroughcrossingsorswitches,bypreventingthepassageofanothertrainonthesametrack,protectionfromatrainmovingintheoppositedirection,trainprotectiononlevelcrossings,ensuringcomplianceofthedriverwithspeedlimits,topreventderailment,assistingbothtrafficsafetyandregularity.

21.2.Semaphoresignaling

21.2.1.Visualandaudiblesignals

Semaphoresignalingismainlyvisual.Audiblesignalsarealsoused,however,mainlyintheeventofthedriverignoringasignaloraspeedlimit.Visualsignalingispermanentortemporary(inthecaseofworksoraccidentsites)andconsistsofdevicesactivatedmechanically.Forthisreason,semaphoresignalingisoftentermedas‘mechanical’.

21.2.2.Colorsusedinsignals

Railwaysignalingusesthesamecolorsasroadsignaling:–redmeansthatthetrainshouldstopimmediately,

–greenmeansthatthelineisclearandthetraincanmovesafely,–yellowiswarningthatspeedshouldbereducedbecauseofanimminentprohibitorysignal(red).

21.2.3.Typesofsignals

Thevarioussignalsmaybeclassifiedasfollows:mainsignals,–homeorentrysignals,–exitsignals,–intermediatesignals,–blocksignals,–protectionsignalscoveringdangerousareas,advancesignals,subsidiarysignals,signalingboards,suchasspeedindicators,directionindicators,etc.

21.3.Operatingprinciplesoflightsignaling–Thetrackcircuit

21.3.1.Definitionoflightsignaling

Semaphoresignalingcannotprovidemaximumsafetytotraintraffic.Thecommunicationprocedurebetweensuccessivestationsbyexchangeofcablemessagesismorereliable,butalsotime-consumingandlargelylimitsthetrackcapacity.Onmainrailwaylines,trafficisaccordinglycontrolledusinglightsignaling.

Lightsignalingconstitutestheelectricalexpressionoftheoperatingregulationoftheparticularline,takingintoaccountthevariousimposedrestrictions.Comparedtotrafficcontrolbyexchangeofcablemessages,lightsignalingcarriesoutautomatically,andthereforewithveryhighreliabilityandspeed,allspecificfunctionsandordersrequiredforthesaferunningoftrains,conditional,ofcourse,onstrictcompliancebytrainpersonnelwiththevarioussignals.

21.3.2.Thetrackcircuit

21.3.2.1.Definition

Aprerequisiteconditionbeforeatrainrunsonatrackistodeterminewhetheranyothertrainispresentatsomepointofthetrack.Thismonitoringiscontinuouslyandautomaticallyperformedbytrackcircuits,whicharethebasisoflightsignaling.

Thetrackcircuitisarailwaysubsystem,whichinasimplifiedapproachconsistsof,(Fig.21.1),(372):–thetworailsofatracksectionAB,–arelayattheentranceAandapowersourceattheexitB,–therequiredinsulatingjointsi,(seeFig.21.1),forthetworailsoftracksectionABinthelongitudinalsense,i.e.eachrailsectionABiselectricallyinsulatedfromtheprecedingandthefollowingrailsection,

–thenecessaryinsulatingmaterialsofeachrailfromthesleepers(andthereforefromtheotherrail).

Fig.21.1.Partsofatrackcircuit

21.3.2.2.Operatingprincipleofthetrackcircuit

Thetrackcircuitisanelectricalcircuitusingthetworailsastransmissionlinesandfedwithalowcurrentbyapowersource.WhennotrainispresentontracksectionAB,(Fig.21.2.a),thecurrentpassesthroughtherelay,whichisactivatedandclosesthesignalingcircuit,causingthesignalingequipmentprecedingsectionABtodisplaya‘lineclear’signal.

AssoonasawheelpairenterstracksectionAB,(Fig.21.2.b),thetworailsareshort-circuitedthroughthewheels-axlesinteraction,therelayisnolongeractivatedandthesignalingcircuitopens,causingthesignalprecedingtracksectionABtoreverttothe‘lineoccupied’signal.

Inordertoreliablydetectthepresenceofarailvehicle,however,atleasttwoaxlesshouldentertracksectionAB.

Fig.21.2.Trackcircuitwithnotrain(a)andwithatrain(b)ontracksectionAB

21.3.2.3.Theblocksection

Whensuccessivetrainsaremovinginthesamedirection,theyshouldbeseparatedbyadistance,termedablocksection,atleastequaltothebrakingdistancedattheparticularspeedandusuallyequalto1.5·d.Inlightsignalingsystems,alineisdividedintosuccessivetrackcircuitsAB,eachconstitutingablocksection.

Atleastonefreetrackcircuitshouldbeinterposedbetweensuccessivetrains.LetusconsiderthetrainpositionsshowninFigure21.3.Thelightsignalattheendofcircuit3isgreen,attheendofcircuit2(precedingcircuit3)isred(noentry),whilethelightsignalattheendofcircuit1(precedingcircuit2)isyellow(warningthedrivertoslowdownbecausearedlightwillfollow).IftwotrackcircuitswerefreebetweentrainAandtrainB,thenthelightsignalinfrontoftrainAwouldbegreen.

Fig.21.3.Lightsignalsinthecaseofsuccessivetrains

21.3.2.4.Typesoftrackcircuits

Thedistancebetweensuccessivestationsmaybedividedintooneorseveraltrackcircuits.Wewillexaminethecaseofonetrackcircuitbetweentwosuccessivestations.

Figure21.4illustratesthesignalingequipmentinastationarea.Thetrackcircuitsofastationaredistinguishedinto:–Trackcircuitattheentrancesofastation(01,04,seeFig.21.4).–Switchtrackcircuit.Thisisthedesignationgiventothetrackcircuitfollowingthetrackcircuitattheentranceofastation.Itincludesallelectricallycontrolledswitchesoneithersideofthestationentrance(02,03).

–Stoptrackcircuit.Thisisthetrackcircuitinthestoppingareaoftrainsarrivingatthestation(I,II).

Fig.21.4.Configurationofasignalingsystemintheareaofastation

21.3.2.5.Trackcircuitrelay

Arelayiscomposedoffourparts:theactuator(Fig.21.5.a),thearmature(Fig.21.5.b),thebase,andthecover.

21.4.Equipmentandpartsofalightsignalingsystem

Alightsignalingsystemiscomposedofthefollowingparts:–traindetectionequipment(alsoincludingeventualtreadles),–lightsignals,–pointthrowingmachines(includingpointdetectors,derailers,stoppingblocks),

–interlockingequipment,–electricalsupplyandfeedingequipment.

Fig.21.5.Partsofarelay(a:Actuator.b:Movingparts)

21.4.1.Lightsignals

Alightsignaliscomposedof:thesignalmast,thelights,theidentificationplate,thetelephonesets,whichenablethedrivertocallthestationdispatcherortrafficcontroller,providedthatthestationincludesremotecontrol.

Thelightsignalsareplacedatthestationentranceandexit.Advancesignalsareplacedtowarnthedriverofthesignalsheisabouttoencounter.

21.4.2.Switchcontroldevices

Inasignalingsystem,theswitchesemployedareusuallyelectricallyactuatedbutalso(thoughnotoften)hydraulicallyorpneumatically,andtheirpositionisautomaticallymonitored.Certainswitches(normallyofsecondaryimportance)maybemanuallyoperated,but,asamandatoryrequirement,theirpositionisagainelectricallymonitored.

21.4.3.Trainintegritydetectors

Entryofthefirstaxlesofatrainintoatrackcircuitdoesnotguaranteethattheentiretrainhasenteredthecircuit,becausepartofthetrainmayhavebeencutoff.Theintegrityofthetrainasawholeisverifiedbythefollowingprocedure.Apermanentmagnetismountedattherearendofeachtrain.Attheentrancetoeachstation,aso-calledtaildetectorislocated.Thisisanelectromagneticdevicemountedonthetrackandactivatedwhenthepermanentmagnetattherearofthetrainispassingaboveit.Useofthis,ratherobsolete,equipmentpermitscheckingtheintegrityofthetrain.

21.4.4.Approachlockingdetectors

Trafficsafetyisensuredwhensuccessivetrainscannotgetcloserthanthebrakingdistance.Therelevantcheckismadebytheso-calledapproachlockingtechnique.

21.4.5.Localoperatinganddisplayboard

Eachrailwaystation,dependingonitstrackconfiguration,itsimportanceandtheestimatedtraffic,isprovidedwithasuitablelocaloperatinganddisplayboard.

Onthisboard,thetrackandswitchlayoutaredisplayedinclearschematicformand,bysuitableluminousindications,thestateofthelightsignalsandthefreeoroccupiedconditionofthetracksortrackcircuitsareindicated.Finally,defectsorfailures,ifany,ofthesignalingsystemareshownbyluminousindicationsonthiscontrolboard.

Thevariousoperationsofthelocalboardarecarriedoutbyoperatingspecifickeys,wherebythestationoperatorspecifiesaroute,assignsatrack,locksanexitlightsignal,etc.Thelocalboardincludescertaincontrols,whicharesealedundernormalconditions.Inamalfunctionemergency,however,itispossibletorestorenormalsystemoperationbyunsealingandoperatingthesecontrols.

21.4.6.Remotemonitoringandcontrol

21.4.6.1.Operatingprinciples

Theremotemonitoringandcontrolsystem,enablingcentraltrafficsupervision,isusedforbettercoordinationandmonitoringofatracksectionorofseveral

successivetrains.Itisthuspossibleforafewoperatorstoregulatethedensesttraffic.

Allinformationinaremotecontrolledstationistransferredbysuitabledevicesanddisplayedonthecentralcontrolboard.Thus,thecentraloperatorhasacompletepictureofthesituationatallstationsinhisareaaswellasofthesituationinthevarioustracks(trainlocations,lightsignalstatus,occupiedtrackcircuits,switchpositions,etc.).Theboardisupdatedautomaticallyandcontinuouslybyspecialhigh-reliabilitycodedsignals.

Thecentraloperatorisprovidedwithacontrolpanelwithvariouskeysandsends,byhigh-reliabilitycodedsignals,thenecessaryinstructionstostationssupervisedbyhim.

21.4.6.2.Equipment

Theoperatingcontrolcenter(orremotemonitoringandcontrolcenter)consistsof,(373):–alloperatingcontrolsanddevicesfortransmissionoftheinstructionstosatellitefacilities.Thelatterareunderstoodtobethestations,trackswitches,blockposts,crossoversatdouble-tracksections,etc.Eachunmannedsatellitepositionisprovidedwitharemote-control-typeuninterruptiblepowersupply,

–allmonitoringdevices,whichperformthroughcolorindicationsonamosaic-typecentralcontrolpanelor,morerecently,onacomputerdisplay,eventuallyprojectedonalargescreen.

21.4.6.3.Remotemonitoring–Controloftrafficsafety

Itshouldbestressedthattheremotemonitoringandcontroldevicesavailabletothecentraloperatorarenottrafficsafetyequipmentbutsimplemeansfortransmissionofinstructionsandreceptionofcorrespondinginformation.Trafficsafetyisatalltimesensured:atsatellitefacilities,bythelocalsafetyinstallation,whichpermitslightsignalstofunctionfollowingallsafetyconditions,attheopenline,bytheautomaticblocksystem,whichregulatesthesuccessionoftrains.

21.4.7.Powersupplyequipment

Theelectricpowernecessaryforoperationofthesignalingsystemissuppliedbythenationalpowernetworkandisdistributedtothevarioussatellitefacilitiesthroughtransformers,rectifiersandotherpowerdevices.

Intheeventofapowerfailure,apowergeneratingcoupleisautomaticallyactivatedateachstation.Finally,inthecaseofmalfunctionofthemotorgeneratorcouple,thesupplyofpowertothesignalingsystemisensuredbyautomaticswitchovertoarechargeablebattery.

21.5.Trainrunningprocedureinalightsignalingsystem

Theuseoftrackcircuitsmakesiteasytolocateatrainatanypointonatrack.Beforeschedulingaroutefromonestationtoanother,theautomaticsignalingsystemchecksbysuitablycodedsignalsthatthetrackbetweentheparticularstationsisandwillremainfreeofanytraffic.Thescheduleisthencarriedout,withthesimultaneousexclusionofanypossibilitytoattemptanotherincompatibleschedule.

Theoperatorofthesignalingsystemensurestheprerequisitesnecessaryforthesaferunningofatrainbymeansofautomaticelectricdevices.Theseprerequisitesarealsoknownassafetyinterlocksandthemainonesaregivenbelow.

21.5.1.Routeinterlock

Uponthearrivalofatrainatitsdestination(orupondeparturefromitsorigin),thetrackswitchesarelockedatthepositionsetbythescheduledrouteandanymodificationoftheirpositionbeforethescheduledtrainrunisprohibited.

21.5.2.Singletrackinterlock

Whenasingletrackcircuitisprovidedbetweentwostations,thentherunningofatrainbetweenthetwostationsrulesoutthemovementofanyothertrainonthatparticulartrack.

21.5.3.Approachinterlock

Thisissuehasbeendiscussedpreviously,(section21.4.4).

21.5.4.Interlockingofoppositeschedules

Schedulingtrainsinoppositedirectionsinstationareasisstrictlyprohibited.

21.5.5.Freewayinterlocking

Insuccessivedepartureandarrivalschedules,thearrivalscheduleshould,asamandatoryrequirement,precedethedepartureschedule.

21.5.6.Lightsignalinterlocking

Theorderofsuccessionofthevariouslightsignalsindicationsisensuredbythefollowinginterlockfunctions:alightsignalmaybeopenedonlyaftertherouteinterlockfunctionisactivated,alightsignalisautomaticallycloseduponfinalizationofaschedule,upontheactivationofalightsignal,theindicationcorrespondingtothetrackswitchpositionsisselected,successionoflightsignalindicationsshouldbedoneinconformitytothetrafficregulation,automaticswitchoverofafailingindication(e.g.duetoalampfailure)toanindicationofahigherorderofsafety.Forinstance,ifayellowentrancesignalfails,theredlightsignalisautomaticallyturnedonwithsimultaneousswitchoverofthegreentoayellowlight.

21.5.7.Compatibleandincompatibleschedules

Onthebasisoftheabove,mutuallycompatibleandincompatibleschedulesarelaidoutforeachcase.

21.6.Speedcontrol

21.6.1.Thevariousspeedcontrolsystems

21.6.1.1.Automaticcontrolanddriverfunctions

Formanydecades,trainswereequippedwiththeso-calleddeadman’shandle(oremergencybrakingswitch).Thisisanobsoletesafetydevice,whichimmobilizesthetrainintheeventthatthedriverlosesconsciousness.Althoughthisisnotaspeedcontrolsystem,itisasafetydevicewhichinthelongrunwassupersededbymoreadvancedautomation,whichmayevensubstituteautomatictrainoperationsystemsforthefunctionsofthedriver.

Thedilemmafacedinrecentyearsiswhethertherailwaysshouldstressautomatictrainoperation(withamarginaldriverrole)ortheactiveroleofthedrivershouldbemaintained,withtheassistanceofadvancedautomationsystems.Thefirstschemecouldbeimplementedonmetrolines,whichare

adequatelyprotectedandhaveuniformtraffic.Onconventionalrailwaylines,however,withamultitudeofswitches,non-uniformtrafficandafrequentneedtoinsertunscheduledtrains,completelyautomatedtrainoperationwouldleadtoinflexibility(asregardsdealingwithunforeseenoccurrences)andtoamarginalroleforthedriver.Thelatter,withnoapparenttask,wouldnotmaintainthevigilancenecessarytodealwithunforeseencircumstances.

Fortheabovereasons,fullyautomatictrainoperationisusedprincipallyinmetrosystems.Inallothercases,theroleofthedriverremainsessential,withcontinuousassistanceandcontrolbytheindispensableautomationsystems.

Boththetrainspeeddatacollectionbyautomaticcontrolsystemsandspeedcontrolitselfmaybeperformedeitheratdiscreteintervalsorcontinuously.

21.6.1.2.Intermittentspeedcontrol

Theintermittentspeedcontroloperatesbeforespeedlimitsignalsattrackswitches,atstationentrancesandexits,etc.Therelevantdatamayberecordedeithercontinuouslyoratdiscreteintervals.

Themethodsemployedmaybeeitherelectromechanical(e.g.theso-called‘crocodile’,atechniqueemployedbytheFrenchrailways),orcontinuouselectricalcommunicationbetweenacontrolpanelandthetrain.Thevariousmethodsincludetheautomaticwarningsystem,usedintheUnitedKingdom,theIndusi,employedbytheGermanrailwaysandthe‘systèmeàbalises’usedbytheFrenchrailways.Theirdifferencesnotwithstanding,allsystemsrelyonthesameoperatingprinciple,(371):ifatthebeginningofaparticularspeedlimit,trainspeedexceedsthespeedlimitby5km/h,thedriverisnotifiedbydistinctiveaudibleandvisualsignals.Ifthespeedlimitisexceededby10km/h,theautomaticbrakingmechanismisactivatedandthetrainisimmobilized.

21.6.1.3.Continuousspeedcontrol

Continuousspeedcontroldependsoncontinuouscommunicationbetweenthetrackandthetrain.Thisisachievedbysuitableequipmentbothinthetrackandinthedriver’scab.

Continuousspeedcontrolalsoinformsthedriveraboutthespecifiedspeed(ateachpointoftheroute)andtheactualspeedateachmoment.

Continuousspeedcontrolisthefirststeptoautomatictrainoperation.Therelevanttechnology(seesection21.6.2.2.below)wasdevelopedintheearly1980sbytheNorwegianandSwedishrailwaysandwaslateradoptedbymanyotherrailwaynetworks,(369).

21.6.1.4.Speedcontrolandinteroperability

Speedcontrolisanessentialfunctionofinteroperabilitysystemsanditisanalyzedbelow(section21.9).

21.6.2.Technicalcharacteristicsoftrainspeedcontrolsystems

21.6.2.1.Electromechanicalcontrol

Inthecaseofelectromechanicalcontrol,ametalbladeassembly,alsoknownasa‘crocodile’,ismountedinthemiddleofthetrack.Ametalbrush,mountedunderthelocomotive,contactstheblades.

Exceedingthespeedlimitorrunningastopsignalcausesaweak8,500HzACvoltagetobeappliedtothebladeassembly.Thisfrequencyissensedbyaspecialreceiveronthelocomotiveandtriggersanaudiblelightsignalwarningthedriver.Shouldthelatterfailtoreactwithin5seconds,thebrakingmechanismisautomaticallyactivatedandthetrainstops,(371).

21.6.2.2.Track-locomotivecontinuouscommunicationsystem

Therelevantequipmentisdistinguishedintounitsmountedonthetrackandunitsmountedonthelocomotive,(371).

Onthetrackaremounted:–ontheonehand,devicestransmittingcodedinformation(concerninggradients,permissiblespeeds,redlightsignalsifany,etc.),

–ontheotherhand,recorders(ofthespeedandotheroperatingparameters)directlyconnectedtothecodedinformationtransmissiondevices.Onthelocomotivearemounted:

Areceiver,receivingthevariousdata,transmittedinanelectromagneticinductionmode,bytheequipmentmountedonthetrack.Advancesinelectronictechnologymakepossiblethetransmissionofalargeamountofdata.Forinstance,intheFrenchTGV,221datacanbetransmittedonacontinuousbasisand228onanintermittentbasis.Acomputer,whichonthebasisofthedatadetectedbythereceiver,determinesthemaximumpermissiblespeed,theactualspeedandvariousotherrouteparametersateachmoment.Luminouspanelsonwhichtheresultsofcomputeranalysisaredisplayed.

21.7.Trainscheduling

Theplanningofatrainschedulenecessitatesthatthevaluesofthefollowing

shouldbedetermined:•approvedmaximumloads,•plannedstoplocations,•runningresistancesandgradients,•inertialcoefficientsofrotatingmasses,•speedlimitsduetothetrack,•speedlimitsduetotherollingstock,•accelerationonstarting,•decelerationonbraking,•brakingdistance.

Operationalcharacteristicsshouldbealsotakenintoaccount,suchas:–requiredtraveltimes,–traincrossing,–bestuseofrollingstock.

Optimizationoftrackcapacityrequiresthegroupingoftrainsintotwocategories:fast(passenger)andslow(freight).Withineachcategory,thespacingoftrainsisrelatedtothespecificspeedandtodistancesofbraking;aspreviouslyanalyzed,thehigherthespeed,thegreaterthebrakingdistance.

Manycomputerprogramshavebeendevelopedandareinusebytherailwaysfortheaccuratecalculationoftrainscheduling.Figure21.6illustratessuchaschedulingforadoubletrack,(370).

Fig.21.6.Extractofaschedulingonadoubletrack

21.8.Calculationofthecapacityofatrack

Thecapacityofatrackisunderstoodasthemaximumnumberoftrainsperhourthatcanrunonasectionofatrack,takingintoaccountthespecificconditionsoftrackandoperation,andassuringasatisfactorylevelofservice.

Forbusytracksequippedwithlaterallightsignals,blocksectionsmayhavealengthof2kmorevenlowerandtrainscanfolloweachotherevery3÷4minutes.Withtheassumptionthattrafficishomogeneous,(i.e.,itiscomposedoftrainswiththesamespeed,samelength,withnostopandsucceedingeachotheratconstantintervals(e.g.,all4minutes)),thecapacityofthistrackperhourwillbe60min/4min=15trains.Unfortunatelythissituationoccursonlyonmetros.Andifadelayappearsinatrain,itaffectsallcomingtrains.

Asrailwaytrafficiscomposedofbothfastandslowtrains,whichmakemanystopsandarenotregularlyspaced,thetargetistoattainapracticalcapacity,whichcanabsorbshortdelaysandbeascloseaspossibletothemaximumtheoreticalone.Twoapproachescanbedistinguished:–increasethetimeintervalbetweensuccessivetrains(forinstancefrom4to5minutes),

–foreveryfivescheduleshaveoneschedulevoid(i.e.withouttraffic).

Inthisway,someshortdelayscanbeabsorbed.Choiceofthemostsuitableapproachismadeinrelationtolocalconditions.Inmanycases,practicalcapacityis60%ofthetheoreticalcapacity,whereasfortrackswithdenseandhomogeneoustrafficitcanreach90%ofthetheoreticalcapacity.

Capacitymaybeincreasedifinsomestationstracksaredesignedsothatfasttrainscanovertakeslowones.Thismethodismoreefficientinthecaseofsingletracksrunbytrainsonbothdirections.

21.9.Interoperability

21.9.1.Definition

Almostallrailwayshavebeendesignedfollowingnationalneedsandpriorities.Asaresult,significantdifferencesexistfromonerailwaytoanotherconcerninggauge,electrificationandsignaling.International(andinmanycasesevennational)railservicesrequirechangesoflocomotivesinthefrontiers(orelsewhere)andinsomecasestransshipmentoffreightandtransferofpassengersfromonetraintoanother.Thissituationcreatesdelays,reducesqualityoftransport,increasescosts,andisnolongeracceptable.

Interoperabilitycanbedefinedastheabilityofarailsystemtoallowthesafeandcontinuousoperationoftrains,whileachievingaspecificlevelofperformance.Thus,interoperabilitycanrefereithertotechnicaloroperationalissuesandmoreparticularlytothefollowingsubsystemsoftherailsystem:infrastructure,energy,maintenance,signalingandcontrol-command,rollingstock,trafficoperationandmanagement,andtelematics.Amongthem,andinordertoassureasafeanduninterruptedrailservice,themostcriticalissuesconcerntrackgauge,electrification,andsignaling.EuropeanUnionDirectives48/1996,16/2001,50/2004,57/2008coverthevariousissuesofinteroperabilityandaredetailedbyrelevanttechnicalspecifications,(134),(333),(361).

21.9.2.Interoperabilityoftrackgauges

Whenavehiclerunsontracksofdifferentgauges,themostefficientwaytoassureinteroperabilityistobeequippedwithaxlesofvariablegauge,whichatthefrontierbetweentwocountries(orwheredifferentgaugesexist)canbeeasilyadjustedfromonegaugetoanother,(366).

21.9.3.Interoperabilityofpowersystems

Anelectriclocomotivenecessitatesspecialdesignandconstruction,whichcanallowmulti-currentormulti-systemoperation,inordertorunonmorethanonepowersystems.Currently,locomotives(liketheThalyshigh-speedtrain)equippedwithsystemspermittingoperationunderthreedifferentpowersystems(25kV50Hz,1.5kV,3kV)areinoperation,aswellaslocomotiveswiththepossibilitytooperateunderfourdifferentpowersystems,(seesection19.7,Table19.3),(367).

21.9.4.TheEuropeanRailTrafficManagementSystem(ERTMS)

Table21.1illustratesthediversityofsignalingsystemsinEurope,withthirteendifferentsignalingandtrafficregulationsystems.TheEuropeanRailTrafficManagementSystem(ERTMS)isaspectacularachievementfortacklingthisproblem.ERTMSiscomposedoftwocomponents:theEuropeanTrainControlandCommandSystem(ETCS)andRadioCommunicationSystem(GSM-R)(whichsendsinformationtothetraindriver).WecandistinguishthreelevelsofapplicationinERTMS:–ERTMSLevel1,(Fig.21.7).Track-basedequipment,usuallytrackcircuitsoraxlecounters,performthedetectionofatrain.Theinformationiscommunicatedtothedriverfromeitherthesidesignalingorusingcabsignaling.Transmissionofdataalongthetrackisrealizedeitherinanintermittentway,

withtheuseoftheEurobalisesystem,orinasemi-continuousway(Eurolooporradioin-fill).

Eurobaliseconsistsofthefollowingcomponents,(Fig.21.7):•theLine-sideElectronicUnit(LEU),whichisacoderininterfacebetweenbaliseandusualsignalingsystems,

•abalisesituatedonthetrack,whichassurestheexchangeofinformationfromonesidebetweensoilandtrain,fromtheothersidebetweenbaliseandLEU,

Table21.1.VarioussignalingandtraincontrolsystemsinoperationinEurope

Fig.21.7.EuropeanRailTrafficManagementSystem(ERTMS)Level1

•anantennaandareceptionsystem,knownasBaliseTransmissionModule(BTM),whichensurestheexchangeofinformationbetweensoilandboard.SignalssentfromtheEurobalisetothebaliseusethefrequencyof27.095MHz(veryclosetothefrequencyof27.115MHzofKVBandEBICABsystems),whereassignalsfromthebalisetoEurobaliseantennaaresentatafrequencyof4.234MHz.,

•anon-boardcomputer(Eurocab),inconstantinterfacewiththedriver,forthecontinuouscalculationofthepositionofatrain,correlation

betweenpermittedandactualspeed,eventualemergencybraking,etc.

IfwewanttoworkERTMSLevel1inasemi-continuousway,thenitisnecessarytoinstalltheEuroloopsystem,whichconsistsofacablerunningalongthetrackandreceivingmessageswhichhavebeensentatfrequenciesbetween1.8÷7.2MHz.

ERTMSLevel1canbeusedbyitselforinsuperpositionofausualsignalingsystem.–ERTMSLevel2.InadditiontothefunctionsofERTMSLevel1,inERTMSLevel2,thetransmissionofdataalongthetrackisdonebytheradio(GSM-R),(Fig.21.8).Thedetectionoftrainsisachievedbytrack-basedequipment,usuallytrackcircuitsoraxlecounters.Informationiscommunicatedtothedriverbycabsignaling.InERTMSLevel2,lateralsignalingisnomorenecessary,butmaycontinuetoco-existwithcabsignaling.Co-existence,however,ofthetwomodesofsignalingmaycauseconfusionorcontradictiontothedrivers.Authorizationforthemovementofatrainismadecontinuouslywiththehelpoftheradiothroughthesoiltothetrain.Inadditiontoensuringinteroperability,ERTMSLevel2implementedintrackswithadensetrafficmayaugmenttrackcapacityby10÷15%,(364).

–ERTMSLevel3.Transmissionofdataalongthetrackisdonebyradio(GSM-R).Thedetectionoftrainsisachievedbytrain-basedequipmentreportingtothecommand-controldataprocessingsystem.Informationiscommunicatedtothedriverinthecab.InERTMSLevel3,thereisnomoreneedfortrackcircuit,(Fig.21.9),whichisreplacedbyasystemofdetectionofthepositionofthetrainandofitsintegrity,(364).

Fig.21.8.EuropeanRailTrafficManagementSystem(ERTMS)Level2

Fig.21.9.EuropeanRailTrafficManagementSystem(ERTMS)Level3

TheERTMStechnologyisimplementednotonlyinEuropeanbutalsoinnon-Europeancountries(amongthem:China,Taiwan,India,Korea,SaudiArabia,Australia,Malaysia,Kazakhstan,Turkey,Brazil,Mexico).In2012,ERTMSwasinoperationon17,000kmoftracksworldwide,morethanhalfofthemoutsideEurope.InstallingERTMSonanewtraincosts0.5million€,whereasonanoldoneitcosts1.5million€.

21.10.Safetymeasuresatlevelcrossings

Levelcrossingsoftenbecometheplaceswhereanumberofaccidentsmayoccur.Levelcrossingswithnotechnicalprotectionshouldnotbeallowedinlinesoperatedwithspeedsabove120km/h,(363).

Levelcrossingsshouldbeeliminatedatthefollowingcases:–crossingswithheavyandslow-movingroadtraffic,–crossingswithheavyvehiclespassingwithaperiodicfrequency,–privateorrarelyusedlevelcrossings,–crossingsreservedforpedestrians.

Safetymeasuresatlevelcrossingsmayincludeoneormoreofthefollowing:roadlightsignaling,halfbarriers,andfullbarriers.Automaticequipmentshouldbeusedexclusively.Thetypeofwarningdeviceadoptedwilldependonthetrainspeed,thetypeofvehiclescrossing(slow,heavy),etc.

Automaticequipmentconsistingonlyofaroadlightsignaling,withoutbarriers,shouldbepermittedonlyexceptionallyandunderveryrestrictiveconditionsforspeedsupto140km/h.

Thesolutionofhalfbarriers,shuttingoffapartoftheroad(thedrivingdirection),canbeusedincombinationwithroadlightsignalingforspeedsupto160km/h.

Fullbarriers,shuttingoffthewholewidthoftheroad,combinedwitharoadlightsignaling,arerecommendedforspeedsabove160km/h,(363).

21.11.Managingrailwaysafety

Whilethesafetylevelofrailtransportisfarhighercomparedtoothertransportmodes,thereexistwaystofurtherincreaserailwaysafety.AccordingtotheInternationalOrganizationforStandardization(ISO),safetycanbedefinedasthereleasefromunacceptablerisks,ariskbeingacombinationofharmprobabilityandgravityofharm.Intherailwaysector,theriskcanbedefinedinrelationtotheeventsthataffectsafety(fatalities,injuriesofpassengersoremployees,seriousmaterialdamages)ortransportationstability(delay).

Accidentsaretheresultofcomplicatedcombinationsofvariousfactorssuchas:thenumberoftrains,thenumberofpassengersandfreight,safetyequipment(signalingandspeedcontrol),thesurroundingenvironment,andhumanfactors.Themostusualformsofrailaccidentsare:collision,derailment,fire,duringmaintenanceworks,withpedestriansatplatforms,etc.,(seealsosection22.5).

Accidentanalysisandmodellingaimtoquantifythedegreeofinfluenceofvariousfactorstotheprobabilityofoccurringthespecificcategoryofaccident.Railwayaccidentsanalysisrequiresanalyticalandaccuratedataandproceedswiththeuseofstochasticmethods.Asaresult,theappropriatemeasurestobetakenaresuggested,e.g.inordertoavoidinaplatformcollisionoraccidentswithpedestrians,warningsystemsdetectingpedestriansorothertrainscanbeinstalledonatrain.

InEuropeanUnioncountries,inordertobegrantedaccesstotherailwayinfrastructure,arailwayundertakingmustholdasafetycertificate,whichistheresponsibilityofeachmember-state,(seealsosection3.6).Anessentialaspectofsafetyisthetrainingandcertificationofstaff,particularlyoftraindrivers.Thetrainingcoversoperatingrules,thesignalingsystem,theknowledgeofroutes,andemergencyprocedures.Therailwayundertakingshouldalsoprovethatitsrollingstockhasbeenproperlycheckedandapproved.

22EnvironmentalEffectsofRailways

22.1.Climatechange,thetransportsectorandsustainabledevelopment

22.1.1.Climatechange

Everyhumanactivityhasaminorormajoreffectontheenvironment.Uptoacertainlevelofindustrialproduction,theenvironmentmayabsorbtheeffectsofhumanactivitiesthroughanaturalprocedure.However,beyondthislevel,climatechangemayappear;thischangeisunderstoodasasignificantandlastingchangeinthestatisticaldistributionofweatherpatternsoverperiodsfromsomedecadestocenturiesorevenmillionsofyears,(375).Theoriginsofclimatechangecanbetracedtohumanactivitiesbutalsotofactorsexogenoustothehumanbeing,suchasoceanicprocesses,solarradiation,platetectonics,andvolcanicactivity.Thequestioniswhetheratthispointwehavereachedalevelofhumanimpactontheenvironment,beyondwhichclimatechangebecomesirreversible.

TheUnitedNationsintergovernmentalpanelonclimatechangehasconcludedsincetheearly1990sthatthebalanceofevidencesuggestsadiscernedhumaninfluenceonglobalclimate.TheanalysesofauthoritiessuchastheNASAmakeclearthat,(375).–theaverageglobaltemperaturehasrisenbetween1900and2000by0.7°Candbetween2000and2010by0.05°C.Ifnochangeoccursintheactualratesofglobalwarming,averagetemperatureswillriseby2.6÷4.7°Cin2100,

–theglobalsealevelhasrisenbetween1900and2000byaround20cmandbetween2000and2010by3cm,withanactualrateofincreaseof3.16mm/year.Ifnochangeoccurs,afurtherriseattheglobalsealevelofmorethan30cmshouldbeexpectedby2100,dueprincipallytothemeltingofpolaricecaps,

–thevolumeofthearcticseaicewasreducedbetween1980and2000by25%andbetween1980and2012byaround40%,

–among600livingbeingstested,morethan75%presentevidencecompatiblewithaneffortofadjustmenttoanincreaseinexternaltemperature,

–knownoilreserveswillbeexhaustedatthelatestby2050÷2060,–therewillbemajorshiftsintheworld’svegetationzones,desertswillbecomehotteranddesertificationwillincrease.

Figure22.1illustratestheevolutionofkeyfactorsofhumanactivityandtheforecastingoftheireventualevolutionuntil2100.

Fig.22.1.Evolutionofkeyfactorsofhumanactivitybetween1900and2100,(391)

22.1.2.Sustainabledevelopment

Awarenessoftheshortageofnaturalresourcesandoftheeffectsofhumanactivitiesontheenvironmenthasledworldinstitutionsandmostgovernmentstotheadoptionoftheterm‘sustainabledevelopment’,whichisunderstoodasthekindofeconomicandsocialdevelopmentinwhichresourceuseaimstomeethumanneedswhilepreservingtheenvironment,sothatfuturegenerationscansatisfytheirneedsandenjoyalevelofprosperitynotverydifferentofthatofgenerationsbetween1950and2010.Principalfactorsfortheachievementofsustainabledevelopmentareeconomicefficiency,environmentalresponsibilityandsocialequity,(376),(392).

22.1.3.Transportandtheenvironment

Thetransportsectorhastogetherwiththeindustrial,tertiaryandhouseholdactivitiessectorsanumberofbadeffectsontheenvironment,suchasairandnoisepollution,consumptionofenergy,accidentsandsafety,landoccupancy,(384).Withinthetransportsector,however,railwaysarethemodeoftransportleastharmfultotheenvironmentandthiscouldproveinthedistantfutureacriticalelementforthedevelopmentofrailways.

Theenvironmentaleffectsofeachtransportmode(road,rail,air,sea)includepassengerandfreighttrafficandmayrefertothefollowing:•constructionandmaintenanceofinfrastructure,•manufacture,maintenanceanddisposalofrailandroadvehicles,airplanes,ships,

•operation.

TheconsumptionoftransportbyindividualsisaffectedbytheirincomeandtheGDPofthespecificcountry(seesection1.3,Figure1.4).AcausalrelationshipcanbeestablishedbetweentheindividualconsumptionoftransportCtrandtheGDPforvariouscountries,asillustratedinFig.22.2.

Fig.22.2.AcausalrelationshipbetweenpercapitaGDPandindividualconsumptionfortransport

Conclusiveevidencesuggeststhatformanydecadesandallovertheworldtheamountoftimethatpeoplearewillingtospendontravelhasremained

remarkablyconstantatapproximately1.1hoursperday.Thismeansthataspeoplehaveanincreasedincome,theymakeuseoffastermodesoftransport,afactleadingtomoreharmtotheenvironment.

22.2.Airpollutionandrailways

22.2.1.Airpollutantsfromrailwaysandothertransportmodes

Transportisanimportantairpollutionemitter,accountingfor90÷95%ofcarbonmonoxide(CO)emissions,60÷70%ofnitrogenoxides(NOx),40÷50%ofhydrocarbons(HC)andvolatileorganiccompounds(VOC),30%ofcarbondioxide(CO2)emissions,5%ofsulfurdioxide(SO2)and25%ofsuspendedmaterials,(379).Table22.1presentstheemissionsofsomeairpollutantsprovokedbythevarioustransportmodesforpassengerandfreighttransport.

Table22.1.Emissionsofpollutantsprovokedbyvarioustransportmodes,(395)

22.2.2.ThegreenhouseeffectandCO2emissionsfromrailwaysandothertransportmodes

Thegreenhouseeffectisattheoriginoftheexistenceoflifeonearth.Indeed,fromthetotalamountofsolarenergyarrivingonearth,30%isreflectedintothespacebytheozonelayerandtheclouds,andtheremaining70%isabsorbedbytheair,theoceansandtheground.Astheearthisheated,itradiatesthisenergy(thegreatestpartofwhichiscapturedbytheso-calledgreenhousegases(ozone,nitrogenoxides,methane,stratosphericwater))intothespace.Thecontributionofgasestothegreenhouseeffectfortheperiod1980÷1990wasasfollows:

carbondioxide50%,chlorofluorocarbons22%,methane13%,troposphericozone7%,nitrousoxides5%,stratosphericwater3%,(376).Withoutthegreenhouseeffect,thetemperatureonearthwouldbe-18°Candofcourselifewouldnotexistinanyrecognizableform.Humanactivitiesduringthelast4÷5decades,principallytheburningoffossilfuelsanddeforestation,haveledtotheincreaseandaccumulationofCO2concentrationsaroundtheearth,afactthatintensifiesthenaturalgreenhouseeffectandcausesglobalwarming.

In2009,thetransportsectorwasresponsibleforthe27EUcountriesfora31.2%oftotalCO2emissions,theothersectorscontributingelectricityandheat37.8%,themanufacturingsector13.2%,theresidentialsector11.3%,theagriculturesector1.5%andtheothersectors4.9%,(379).Withinthetransportsector,contributionofthevarioustransportmodesinCO2emissionswasforthe27EUcountriesfortheyear2009asfollows:roads71.0%,navigation14.3%,aviation12.3%,railways1.8%,other(non-specified)0.5%.However,changesbetween1990and2009inCO2emissionsfromfuelcombustionforthevarioustransportmodesareillustratedforthe27EUcountriesinFig.22.3.

Fig.22.3.ChangesinCO2emissionsfromfuelcombustionbythevarioustransportmodesforthe27EUcountriesbetween1990and2009,(379)

22.2.3.CO2emissionsbythevarioustypesoftrains

Figure22.4illustratestheevolutionofCO2emissionsforpassengerandfreighttrainsbetween1990and2009.Figure22.5givesspecificCO2emissionsfordieselandelectrictractionfortheyear2009andFigure22.6CO2emissionsbyservicetype(high-speed,intercity,regional)fortheyear2005.ComparativeCO2

emissionsofrailwaysandtheircompetitorsaregivenforthe27EUcountriesinFigure22.7.

22.2.4.Carbontax,internalizationofexternalcostsandrailways

Inordertoreducethegreenhouseeffect,theKyotoagreementimposes(tothestateswhichhavesignedit)areductionofCO2emissionsduringtheperiod2008÷2012by5.2%comparedtothelevelsemittedin1992.

Fig.22.4.CO2emissionsofpassengerandfreighttrainsforthe27EUcountries,(379)

Fig.22.5.SpecificCO2emissionsfordieselandelectrictractionforthe27EUcountriesfortheyear2009,(379)

Fig.22.6.SpecificCO2emissionsforhigh-speed,intercityandregionaltrainsforelectricanddieseltractionforthe27EUcountriesin2005,(379)

Fig.22.7.ComparativeCO2emissionsofrailwaysandothertransportmodes,(379)

AsawaytoconfrontthegreenhouseeffectandCO2emissions,acarbontaxof20.0USdollarspertonofcarbonemittedhasbeensuggested.Ifthisinternalizationproceeds,somethingthatisnotverylikely,ashiftoftraffictotherailwayscanbeexpected.Assessmentofthisshiftoftrafficmaybeapproachedasfollows,(15).

Firstadecisionshouldbemadewhether:-internalizationshallincludeonlyCO2emissionsorallexternalcosts,-internalizationshallbebasedonmediumexternalcostormarginalsocialcost.

Astudyontheinternalizationofexternalcostsforthe27EUcountrieswasbasedontheincreaseofoperationcoststhatwillresultandoncross-elasticities

betweenrailandothertransportmodes.Ifinternalizationisconductedaccordingtomediumexternalcosts,expectedshiftoftraffictotherailwayswouldbeontheorderof12÷15%forpassengerandupto24%forfreight.If,however,internalizationisconductedaccordingtothemarginalsocialcost,theexpectedshiftoftrafficforpassengerandfreightwouldbeontheorderofonly6%,(15).

22.3.Railwaynoise

22.3.1.Sourcesanddampingofrailwaynoise

Sourcesofnoisefromrailtraffichavebeenanalyzedinsection8.9.1andare;•noisefromtheenginesofrollingstock,•noisefromwheel-railinteraction,plus(forelectrifiedlines)noisefromthecontactbetweenthepantographandthecontactwire(seealsosection20.8),

•aerodynamicnoise,

Figure22.8illustratesnoiselevelsforthesethreesourcesofrailwaynoiseinrelationtospeed,(380).Apparentlytotalnoiseisnotthesumofthethreesourcesofrailwaynoise.Figure22.8illustratesthatatlowspeeds(V<100km/h)noisefromtheenginesofrollingstockisdominant,atmediumspeeds(100km/h<V<200km/h)wheel-railnoiseisdominant,whereasathighspeeds(V>200km/h)aerodynamicnoiseisdominant.Concerningtraintype,however,theimpactofthevarioussourcesofrailwaynoiseisdifferent(Table22.2),(380).Noiselevelsareattenuatedbydistance(thoughnon-linearly)andareinfluencedmorebydistancethanbychangesinspeed(seesection8.9.3).Resultsofmeasurementsofnoiselevelinrelationtodistance,thetypeoftrain,andthespeedwerepresentedinsection8.9.5.

Fig.22.8.Noiselevelofthevarioussourcesofrailwaynoise,(380)

Table22.2.Importanceofsourcesofrailwaynoiseinrelationtotraintype,(380)

22.3.2.Noiseindicatorsandmaximumpermittedlevelofrailnoise

AccordingtotheEuropeanDirective49/2002,relatedtotheassessmentandmanagementofenvironmentalnoise,theso-calledday-evening-nightlevelLden

shouldbeusedasabasicnoiseindicator,whichcanbedefinedasfollows,(380):

inwhich:-LdayistheA-weightedlong-termaveragesoundleveldeterminedoverallthe

dayperiodsofayear,-LeveningistheA-weightedlong-termaveragesoundleveldeterminedoveralltheeveningperiodsofayear,-LnightistheA-weightedlong-termaveragesoundleveldeterminedoverallthenightperiodsofayear.

Thedayisconsideredtohave12hours,theevening4hoursandthenight8hours.However,theeveningperiodmaybeshortenedby1÷2hoursandthedayornightperiodlengthenedby1÷2hoursaccordingly,(380).

TheEuropeantechnicalspecificationsforinteroperabilitysetthemaximumnoiseemissionforhigh-speedtrainsatthelevel82÷87dB(A),(134),(380).Theselevelsareatleast10%lowerthanthecurrentemissionlevelsinadvancedrailways,liketheGermanrailways.

However,recommendationsoftheWorldHealthOrganization(WHO)fornoiselevelinlivingorworkingareasarefarlower;forinstanceinordernottodisturbpeople’ssleep,noiselevelinsleepingroomsshouldnotexceed30dB(A).Thus,theneedtoattenuateanddampenemittednoiselevelsemerges.

22.3.3.Measuresforreductionofrailnoiseandrelatedcosts

Themostefficientstageforthereductionofrailnoiseisduringthedecisionmakingprocessconcerninglayout.Infact,layoutdesignonembankment,viaductandbridgeresultsinnoiselevelsattherangeof75÷105dB(A),whereaslayoutdesignincutresultsinnoiselevelsattherangeof50÷75dB(A),(seesection8.9.4),(163),(388).

Otherwaystoreducerailnoiseattheoriginare,(379):–reductionofnoiseofthedieselengine(EuropeanDirective26/2004putsmorestrictterms),

–appropriategrindingofrails,(seesection16.8),–compositebrakeshoes,whichinthecaseoffreighttrainscouldsignificantlyreducetheemittedlevelofrailnoise.

Ifrailnoisecannotbereducedattheorigin,thenthesolutionispassivemethodsofreduction,withmostefficientamongthemtheuseofnoisebarriers,(385).These,shouldbeplacedascloseaspossibletothetrack,andhavesuchaheightthatthereisnodirectvisualcontactbetweenthereceiverofthenoiseandthewheeloftherailvehicle.Implementationofnoisebarriers(ofanon-absorbingmaterial)ataheightof2mandadistanceof3.50mfromthetrackresultsinareductionoftheperceivednoisebyapproximately10dB(A).If,in

addition,noisebarriershaveanoiseabsorbingmaterialatthesideofthetrack,noisereductionisfurtherincreasedby2÷5dB(A).Noisereductionwiththeuseofbarriersisnotaffectedbytrainspeed,(170).

Table22.3(nextpage)illustratesthesourcesofrailwaynoise,suggestedmeasuresforthereductionofnoise,expectedresults,andestimatedcosts.

22.4.Energyconsumptionandrailways

22.4.1.Energyconsumptionandthetransportsector

Forthe27EUcountriesintheyear2010,thetransportsectorconsumed31.7%oftotalenergy,households27.7%,industry25.3%,services13.2%,agriculture2.2%,otheractivities1.9%.Percentagesoftheconsumptionofenergyattheworldlevelwerefortheyear2010asfollows:transport27.3%,industry27.8%,domesticandtertiarysector36.0%.Worldenergydemandwassatisfiedin2006fromfivemainsources:oil37.8%,gas23.8%,coal25.6%,nuclear8.1%,hydroelectric6.1%,alternative0.9%.Whileaglobaloilshortageshouldbeexpectedaround2050÷2060,knowngasreserveswillcontinuetoservetheplanetandsatisfyworlddemandwithoutexcessivepricesatleastuntil2100÷2150,(379).

22.4.2.Energyconsumptionwithinthetransportsector

Withinthetransportsectorforthe27EUcountriesintheyear2009,railwaysconsumed2.6%oftotalenergyfortransportactivities,roadtransport71.9%,navigation13.0%,airtransport12.1%andothernon-specified0.4%,(379).Figure22.9illustratestheevolutionofenergyconsumptionbytransportmodefrom1990to2009forthe27EUcountries,(379).

22.4.3.Energyconsumptionfordieselandelectrictraction

Figure22.10illustratesforthe27EUcountriesintheyear2009,whatpartofenergyconsumedbyrailwaysisusedfordiesel(28%)andelectric(72%)traction.However,thesituationmaywellbetotallydifferentinotherpartsoftheworldwithfewerkilometersofelectrifiedlines.

Table22.3Sourceofrailwaynoise,suggestedmeasure,levelofimpact,expected

reductionofnoiseandestimatedcost,(380)

Fig.22.9.Evolutionofenergyconsumptionofthevarioustransportmodesforthe27EUcountries,(379)

Figure22.10.Consumptionofenergyfordieselandelectrictractioninthe27EUcountries,(379)

22.4.4.Specificenergyconsumptionofrailwaysandothertransportmodes

Figure22.11illustratesspecificenergyconsumptionperunittransported(passenger-km,ton-km)forrailwaysandothertransportmodes.Duetotechnicalinnovationsintroducedduringrecentyears,specificenergyconsumptionhasbeensubstantiallyreduced,asisillustratedforthe27EUcountries(Fig.22.12).

Inotherpartsoftheworld,thereductionofthespecificenergyconsumptionofrailwaysbetween1990and2009wasasfollows:USA50%,China63%,India71%,Russia17%,(379).

Specificenergyconsumptionforbothconventionalandhigh-speedtrainsisintherangeof28÷39wh/seat-kmandisnotsignificantlyaffectedbyspeed(Fig.22.13),butisstronglyaffectedbylongitudinaltrackgradient(Fig.22.14).Notethat1kwh=3,600kJ.

Fig.22.11.Specificenergyconsumptionofrailwaysandothertransportmodes(395)

Fig.22.12.Evolutionofthespecificenergyconsumptionofrailwaysforthe27EUcountriesbetween1990-2009,(379)

Fig.22.13.Energyconsumptionofpassengertrainsinrelationtospeed,(379)

Fig.22.14.Energyconsumptionofpassengertrainsinrelationtospeedandlongitudinalgradient,(379)

However,thevaluesofspecificenergyconsumptionforrailfreightmaypresentagreatrange,duetotheheterogeneityofrollingstock.Figure22.15illustratesforvariousfreighttransportmodeswhatdistancecanbetraveledfor1tonoffreightwhenusing1kwhofenergy.

Fig.22.15.Distancetraveledbyvarioustransportmodesfor1tonoffreightwhenusing1kwhofenergy,(379)

22.5.Energyconsumedinrailwaysforcomfortfunctions

Energyconsumedbyelectrictrainsiseasytomonitoranalyticallyperpointoftrackandcanbebrokendownin3categories:•energyrequiredtoovercomethetrain’sresistancetomovement(rollingresistances,mechanicalresistances,aerodynamicresistances)(seealsosection18.3),

•energyrequiredtoprovidecomfortfunctionstopassengersduringtraveling,•energylostbetweensubstations-pantographandpantograph-wheel.

Figure22.16illustrateshowenergyisconsumedinelectrictrains(conventionalandhigh-speed).Whatbecomesevidentisthepositiveeffectofusingregeneration,thatis,regenerativebraking,whichfeedsbackintothecatenarypower;otherwisethiswouldbedissipatedandlost.

Oilpricespresentirregularities,(seeFig.1.3),asaresultofeconomicfactors(recession-growth,needsofemergingeconomies),politicalfactors(embargos,wars),thespeculationofstockmarkets,psychologicalfactors(fearsofshortage).However,dependingontheloworhighvaluesofoil,fuelcostsasapercentageoftotaloperationcostsamountto6÷10%forrailwaysandtrackingcompaniesand15÷30%foraircompanies.Thus,fluctuationsinoilpricesdonotcriticallyaffectthecompetitivepositionofthevarioustransportmodes.

Fig.22.16.Consumptionofenergyforvariouscategoriesofelectrictrainstoovercomeresistancesandassurecomfort,(379)

22.6.Accidents,safetyandrailways

22.6.1.Definitionofrailwayaccidents

Safetyisacentralconcernforalltransportmodes.Railwayaccidentsattracttheattentionofmediaandthepublic,astheyarespectacularevents(togetherwithaircraftcrashes).However,comparedtorailways,theriskofdeathis7timesgreaterwhenusingacarand2timesgreaterwhenusingabus.Theeconomiceffectsofaccidentsinalltransportmodesamountforthe27EUcountriesto2%oftheirGDP,(95).

AccordingtotheEuropeanRegulation1192/2003,asignificantrailaccidentisanyaccidentinvolvingatleastonerailvehicleinmotion,resultinginatleastonekilledorseriouslyinjuredpersonorinsignificantdamagetorollingstock(atleast150,000€),track,otherinstallationsortheenvironmentorextensiveinterruptionintraffic.Accordingtothisdefinition,accidentsinworkshops,warehousesanddepotsareexcluded.

22.6.2.Typesofrailwayaccidents

Railwayaccidentsincludethefollowingtypes:collisions,derailments,accidentsinvolvinglevelcrossings,accidentstopersonscausedbyrollingstockinmotion,andfiresinrollingstock.

Table22.4illustratestheeffectsofrailwayaccidentsonthe27EUcountriesfortheyear2011,duringwhich2,685significantrailaccidentsoccurredwith2,325personskilledorseriouslyinjured,(377).

Inthetotalnumberofdeathsoccurringinrailwayaccidents,fatalitiesofpassengersaccountfor5%,ofemployeesfor2%,oflevelcrossingusersfor29%,ofunauthorizedpersonsfor60%andothersfor4%.

Table22.4.Effectsofrailwayaccidentsinthe27EUcountriesandfortheyear2011,

(377)

22.6.3.Causesofrailwayaccidents

Causesofrailwayaccidentsmaybeidentifiedasfollows,(377):–defectsinlevelcrossings,–falseswitching,–collisionwithbuses,cars,trucks,–defectsintheequipmentoftraincontrol,–defectivesignalsorfalseinformationtothetraindriver,–inadequatemaintenanceofthetrack,whichmayleadtoderailment,–mechanicalfailuresofwheelsandrails,–earthquakewhilethetrainismoving,–collapsedbridge,–improperloadingorunloadingofcargo,–trainstaffwhichiseitheruntrainedorundertheinfluenceofdrugsoralcohol.

22.6.4.Measurestoincreaserailwaysafety

Railwaysafetycanbeincreasedoncecertainmeasuresareundertaken.Thesemeasuresareasfollows,(377):

•installtheappropriateprotectionsystemsinlevelcrossings,•improveoperationalsafetysystems,suchastheautomatictraincontrolsystem,•installmonitoringsystemswhichidentifyanydefectivematerialoroperation,•improvetheeducationofallrailwaystaff,•forseparatedrailways,ensurethemaximumlevelofcooperationbetweeninfrastructureandoperation,

•informtheclientsandmoregenerallythepubliconthedangersrelatedtotherailwaysystem(thoughsmallercomparedtoothertransportmodes).

Railwaysareconstantlytryingtoreducethenumberoflevelcrossingsperkilometeroftrack,whichin2010forthevariouscountriesoftheEUwasattherangeof0.15÷1.00levelcrossingsperkmoftrack.

Inaddition,itissuggestedtoinstallautomaticormanualprotectionsystemsatthemaximumnumberoflevelcrossings,oratleastinthemostdangerousones.PercentagesoflevelcrossingswithsomekindofprotectionforthevariousEUcountriesbetween20%÷100%,(377)

Railwaysafetymaybeconsiderablyincreasedwiththeuseofautomatictraincontrolsystems.ThepercentageoftracksequippedwithsuchsystemsforEUcountriesrangesbetween14%÷100%.

22.6.5.Evolutioninthenumberofrailwayaccidents

Allrailwayshaveundertakenmeasurestoreducerailwayaccidents,somethingthatisreflectedintheratioofaccidentsandfatalitiesreportedtototalrailtraffic.Figure22.17illustratesthereductionofrailaccidentsduringthelast35yearsintheUnitedKingdom.

22.6.6.Accidentswhentransportinghazardousmaterials

Manydangerousgoodsandhazardousmaterialsarebeingtransportedbyrail.Ifanaccidentoccursduringsuchatransport,itmayhavecatastrophiceffectsnotonlytopeoplebutalsototheenvironment.

Fig.22.17.EvolutionofrailwayaccidentsintheUnitedKingdom,(377)

Quantitativeriskassessmentofthetransportofhazardousmaterials(withthemostdangerousamongthem:hydrogencyanide,phosgene,anhydrousammonia,chlorosulfonicacid,hydrogenperoxide,methanol,titaniumdioxide,andethyleneglycol)continuestobeataninfantstageofdevelopment,plaguedbyproblemsofrecognition,precisionandcredibility.Effectsmayrefertoindividualsinspecificlocations(individualrisk)ortothesocietyingeneral(societalrisk).Comparativeanalysisofthetransportofhazardousmaterialsinsomespecificrouteswiththeuseofrailandroadhasgivenforrailariskfactorsixtimeslowercomparedtoroad.Emphasisshouldbeplacedonthefactthatmeasuresshouldaimatreducingriskandnotatshiftingtheproblemtoanotherareaofthedistributionsystem,(393),(394).

22.6.7.Railwayaccidentsandsafetycertification

Directive14/2001oftheEUrequiresforeveryrailoperatorwithintheEUtopossessasafetycertificate,issuedbyeachstateandvalidwithinthespecificstate.Anharmonizationofprocessesandprerequisitesforissuingthesafetycertificatemayalsocontributetoincreaserailwaysafety.

22.7.Landoccupancy,landscape

Transportinfrastructureoccupyspacethatcanhaveotherusesinurbanandnon-urbanareas.Awarenessofthiseffectismoreapparentindenselypopulatedcountries,suchasJapan,theNetherlands,Belgium,etc.

Ifthecarryingcapacityofalltransportmodesiscomparedtotheirlandoccupancy,thenrailwayshaveaclearadvantage,sincethespacerequiredbya

privatecarpassengeris22timescomparedtorail,andbyabuspassenger1.7timescomparedtorail.

Inaddition,alltransportinfrastructurecauseaminorormajoreffecttothelandscapeandenvironmentalaesthetics.Railwaysaremoreeasilyinsertedintotheenvironment,particularlyiflayoutdesignhasthemaximumnumberofsectionsincutasopposedtoembankment.Inanycase,theplantingoftreesalongthetrackshouldfollowanyconstructionoftrack.

Theproblemofrecyclingmaterialsusedforrollingstockandinfrastructureisanotherissue.Manyrailwayshaveadoptedastrategytorecyclethemaximumamountofrollingstockandtrackmaterials,toorientprocurementsformoreecologicalprotectionandtocontrolweedalongthetrackwithoutdoingharmtotheenvironment.

22.8.Congestion

Railways,owingtotheirgreatcarryingcapacity,(seesection1.2.1),canalleviatetrafficcongestion.Thetotalannualcongestioncosthasbeenevaluatedforthe25countriesoftheEuropeanUnion+Norway+Switzerlandatapproximately200billion€andfortheUSAatapproximately100billion$(valuesofyear2011),(95).Congestioncostisthesumoftimelossesbypassengersandtheincreaseofoperationcost,duetolowspeeds.Acriticalassumptioninthecalculationofcongestioncostsisthevalueoftimeperman-hour(forpassenger)orperwagonorton-hour(forfreight).Thefollowingvalues(convertedin€ofyear2008,basedoninitialvaluesandinflationrates)oftraveltimehavebeenusedinsomestudiesforrailways,(105),(381):–businesstravel17.25÷25.00€/man-hour,–commutingtravel8.75€/man-hour,–leisuretravel6.10÷7.00€/man-hour,–freighttransport1.05÷1.30€/ton-hour,

Congestionissuesareinfluencednotonlybytheassessmentoftechnicalandeconomicfactorsfromusers,butalsoofusers’choicesfortheirpreferredlifestyle,whichduringthelastthreedecadesfavorstheuseoftheprivatecarandtheairplane.

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169.ProfillidisV.,(1983),LesLoisdeComportementNon-LinéairesenMécanique-TraitementparlaMéthodedesElémentsFinis,Textbook,FrenchRailways,Paris.

170.ORE,C137,RP12(1981),‘RailwayNoise:MeasurementsoftheRunningNoisecausedbyTrainsonDifferentTypesofBridges’,Utrecht.

171.GirardiL.,(1981),‘PropagationdesVibrationsdanslesSolsHomogènesouStratifiés’,Inst.Techn.duBat.etdesTrav.Publ.,No397.

172.ChangC.,AdegokeC.,SelligF.,(1980),‘GeotrackModelforRailroadTrackPerformance’,ASCE,Journ.ofGeotechn.Eng.,Vol.106,No11.

173.ZienkiewiczO.,(1980),TheFiniteElementMethodinEngineeringScience,McGraw-Hill.

174.LópezPitaA.,OteoMazoC.,(1978),‘AnálysisdelaDeformabilidáddeunaViaFérreaMedianteelMétododeElementosFinitos’,AIT,No15.

175.ORE,D71,RP9,RP10(1978),StressintheTrack,BallastandtheSubgradeundertheActionofRepeatedLoading,Utrecht.

176.EisenmannJ.,(1977),DieSchienealsTrägerundFahrbahn,VerlagErnst,Berlin.

177.ZienkiewiczO.,ValliapanS.,King,I.,(1969),‘ElastoplasticSolutionsofEngineeringProblems.InitialStress-FiniteElementApproach’,Int.Journ.ofNum.Meth.inEngin.,Vol.1.

178.ZimmermannH.,(1941),DieBerechnungdesEisenbahnoberbaues,ThirdEdition,WilhelmErnstundSohn,Berlin.

CHAPTER9179.MortezaE.,HamidrezaH.-N.,(2013),‘InvestigatingSeismicBehaviorof

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180.BudhimaIndaratna,(2010),‘FieldAssessmentofthePerformanceofBallastedRailTrackwithandwithoutGeosynthetics’,ASCE,Journ.ofGeotechn.&Geoenvir.Eng.,Vol.136,Issue7.

181.JianKurnLiu,JunhuaXiao,(2010),‘ExperimentalStudyoftheStabilityofRailroadSoftSubgradewithIncreasingTrainSpeed’,ASCE,Journ.ofGeotechn.&Geoenvir.Eng.,Vol.136,Issue6.

182.QueroD.,DoanV.-T.,(2002),‘PriseenComptedel’AléasSismiquedelaLigneduTGVMéditerranée’,RGCF,February2002.

183.PerletJ.,(2002),‘LesAménagementsHydrauliquesdelaLigneduTGVMéditerranée’,RGCF,February2002.

184.BowlesJ.,(2001),FoundationAnalysisandDesign–5thEdition,McGraw-Hill,NewYork.

185.ProfillidisV.,(2000),‘TheReinforcementEffectofGeotextilesinRailwaySubgrades’,RailInternational,No7.

186.UIC,Fiche719R(1994),OuvragesenTerreetCouchesd’Assise

Ferroviaires,Paris.187.UIC,Code723R(1992),SelectionandUseofWeedkillersalongside

RailwayTracksfromtheStandpointofEnvironmentProtection,Paris.188.CarterM.,BentleyS.,(1991),CorrelationsofSoilProperties,Pentech

Press,London.189.UIC,Code722R(1990),MethodsofImprovingtheTrackFormationof

ExistingLines,Paris.190.ProfillidisV.,(1985),Geotextiles–MechanicalandHydraulicBehavior–

Applications,Textbook,Thessaloniki.191.ProfillidisV.,KouparoussosA.,(1984),‘MechanicalBehaviorofthe

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192.RoweK.,(1984),‘ReinforcedEmbankments:AnalysisandDesign’,ASCE,Journ.ofGeotechn.Eng.,Vol.110,No2.

193.SociétéNationaledesCheminsdeFerFrançais,(1982),OuvragesenTerreArmée,Paris.

194.NaylorD.,PandeG.,SimpsonB.,TabbR.,(1981),FiniteElementsinGeotechnicalEngineering,PineridgePress.

195.ORE,D117,RP15,16(1981),FiltrationetDrainage,Utrecht.196.Sauvage,R.,Langlade,J.(1981),‘L’UtilisationdesGéotextilesdansles

Plates-formesFerroviairesdelaSNCF’,RGCF,July-August1981.197.RankilorD.,(1981),MembranesinGroundEngineering,JohnWiley.198.HartmarkH.,(1979),‘FrostProtectionofRailwayLines’,Engin.Geology,

Vol.13,Amsterdam.199.UIC,Question714(1978),AdaptationdelaPlate-formedansl’Optique

desCirculationsàGrandeVitesseetdel’AugmentationdelaChargeparEssieu,Paris.

200.TirantP.,SardaJ.,(1965),‘ChargementsRépétésdesSolsFinsCompactésetNonSaturés’,Bull.deLiaisondesLabor.desPontsetChaussées,(LCPC),July-August1965.

201.AyresD.,(1961),‘TheTreatmentofUnstableSlopesandRailwayTrackFormations’,Journ.oftheSoc.ofEngineers,Vol.52,No4.

CHAPTER10202.IgnestM.etal,(2012),‘DevelopmentofaWearModelforthePredictionof

WheelandRailProfileEvolutioninRailwaySystems’,Wear,April2012.203.SalehiI.,KapoorA.,MuttonP.,(2011),‘Multi-axialFatigueAnalysisof

AluminothermicRailWelds’,Intern.Journ.ofFatigue,Vol.33,No.9.204.BetegonB.etal,(2009),‘NonlinearAnalysisofResidualStressesinaRail

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205.Innotrack,(2008),‘InnovativeTrackSystems’,Brussels.206.Thyssen,(2005),RailSections.207.UIC,(2005),Leaflet721,‘RecommendationsfortheUseofRailSteel

Grades’,Paris.208.ORE,D185,RP3(1997),TheoreticalModellingofRailCorrugationsand

ValidationbyMeasurement,Utrecht.209.ProfillidisV.,(1991),‘MechanicalBehavioroftheRail’,ProfessorG.

Nitsiotas’sHonoraryVolume,UniversityofThessaloniki.210.EdelK.,OrtmannR.,(1990),‘Fracture–MechanicalCharacteristicsofRail

Materials’,RailInternational,August-September1990.211.TassilyE.,(1987),‘PropagationdesOndesdeFlexiondanslaVoieFerrée

consideréecommeunMilieuPériodique’,RGCF,March1987.212.ProfillidisV.,(1986),‘ContinuousWeldedRail’,BulletinofGreekCivil

Engineers,No172,Athens.213.UIC,860(1979),TechnicalSpecificationfortheSupplyofRails,Paris.214.SperringD.,SquiersJ.,(1983),‘RailWearandAssociatedProblems’,

BritishRailwayTrackCourse.215.MairR.,GroenhoutP.,(1981),‘CroissancedesDefectuositésTransversales

duesàlaFatiguedansleChampignondesRailsdeChemindeFer’,RailInternational,February1981.

216.TounendP.,(1980),‘AnalysedelaProbabilitéetCoûtdesDéfautsenFormedeTacheOvaledusàlaFatiguedesVoiesenAlignementetenCourbedansdesConditionsdeFortesChargesparEssieu’,RailInternational,July-August1980.

217.ORE,D141,RP1(1979),StatisticalStudyoftheEvolutionofRailDefectsinRelationtotheMediumAxleMass,Utrecht.

218.UIC(1979),CatalogueofRailDefects,Paris.219.DangVanK.,GenceP.,(1978),‘EvolutiondesCritèresdeFatigue-

ApplicationaucasdesRails’,RGCF,December1978.220.FowlerG.,(1976),FatigueCrackInitiationandPropagationinPearlitic

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222.EisenmannJ.,(1970),‘StressDistributioninthePermanentWayduetoHeavyAxleLoadsandHighSpeeds’,AREA,Vol.71.

223.ORE,D71,RP2(1966),StressDistributionintheRails,Utrecht.224.YasojimaY.,MachiiK.,(1965),‘ResidualStressesintheRail’,Permanent

Way,Vol.8,No26.225.TimoshenkoS.,LangerB.,(1932),‘StressinRailroadTrack’,ASME,Vol.

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228.ProfillidisV.,(2001),‘TheMechanicalBehavioroftheRailwaySleeper’,RailInternational,No1.

229.EuropeanStandard,(1994),‘Twin-BlockReinforcedConcreteSleepers’,EuropeanCommitteeforStandardization,Brussels.

230.EuropeanStandard,(1994),‘PrestressedMonoblockConcreteSleepers’,EuropeanCommitteeforStandardization,Brussels.

231.BonewitzW.,FuhrerG.,(1992),‘EinsatzvonElastomerenbeiSchienen-befestigungbeiEisenbahnenundNahverkehrsbahnen’,DieBundesbahn,No3.

232.SATEBA(1992),Twin-BlockRailwaySleepers,Paris.233.FIP(FédérationInternationaledelaPrécontrainte),(1987),Concrete

RailwaySleepers,ThomasTelfodEditions,London.234.ProfillidisV.,PoniridisP.,(1986),‘TheMechanicalBehaviorofthe

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Pads’,TrackCourse,RIA,London.238.HodgsonW.H.,(1983),‘SteelSleepers’,TrackCourse,RIA,London.239.UIC,863V(1981),TechnicalSpecificationfortheSupplyofNon-treated

TrackSupport(WoodenSleepersforStandardandBroadGaugeTrackandCrossingTimbers),Paris.

240.AmericanRailwayEngineeringAssociation(1982),ConcreteTies.

241.ORE,D71,RP8,(1973),LoadDistributionundertheSleeper,Utrecht.242.ORE,D71,(1973),SollicitationdelaVoie,duBallastetdelaPlate-forme,

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CHAPTER12243.TrinhV.-V.etal,(2012),‘MechanicalCharacteristicsoftheFouledBallast

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244.BuddhimaIndraratna,(2010),‘ExperimentalandNumericalStudyofRailwayBallastBehaviorunderCyclicLoading’,ASCE,Journ.ofGeomechanics,Vol.10,No4.

245.SuikerA.,M.,SeligE.,FrenkelR.,(2005),‘StaticandCyclicTriaxialTestingofBallastandSubballast’,ASCE,Journ.ofGeotechn.andGeoenviron.Eng.,Vol.131,No6.

246.EuropeanStandardEN13450,(2002),AggregatesforRailwayBallast,EuropeanCommitteeforStandardization,Brussels.

247.SchmutzG.,(2000),‘BallastandRe-useofoldBallast’,RailInternational,July-August2000.

248.ORE,D182,RP4(1995),StandardizedTechnicalSpecificationsandDescriptionoftheQualityAssuranceSystemforRailwayBallast,Utrecht.

249.ProfillidisV.,(1988),‘MechanicalBehavioroftheRailroadBallast’,1stCongressofGeotechnicalMechanics,Athens.

250.Gray,P.S.(1983),‘StructuralRequirementsandSpecificationsofBallast’,TrackCourse,RIA,London.

251.StewartH.,SeligE.,(1982),‘PredictionsofTrackSettlementunderTrafficLoading’,2ndInternationalHeavyHaulConference,ColoradoSprings,September1982.

252.SNCF,(1979),ConstitutiondelaVoieCourante,Paris.253.RaymondG.,DaviesJ.,(1978),‘TriaxalTestsonDolomiteRailroad

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Journ.ofGeotechn.Eng.,Vol.104,No6.255.LopezPitaA.,(1977),‘AnalysedelaDéformabilitéduBallastaumoyend’

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256.ORE,D117,RP5(1974),DeformationofTrackBallastunderRepeatedLoading,Utrecht.

257.ShentonM.J.,(1974),DeformationofRailwayBallastunderRepeatedLoadingTriaxialTest,SoilMech.Sec.,BritishRailwaysRes.Dept.

CHAPTER13258.KocW.,(2010),‘DeterminationoftheTransverseResistance

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RGCF,April1987.261.ProfillidisV.,(1987),‘ParametricAnalysisofTransverseTrackResistance

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262.UIC,720R,(1986),LayingandMaintenanceofTrackmadeupofContinuousWeldedRails,Paris.

263.ORE,C138,RP8(1984),PermissibleMaximumValuesfortheY-andQ-ForcesandDerailmentCriteria,Utrecht.

264.ORE,B55,RP8,(1983),PreventionofDerailmentofGoodsWagonsonDistortedTracks,Utrecht.

265.ORE,C138,RP7,(1982),InfluencedesVariationsOscillatoiresdelaCharged’EssieusurlaValeurMaximaleAdmissibledel’EffortTransversaleduPointdeVuedeDéripagedelaVoie,Utrecht.

266.ErchkovO.P.,KartzevV.J.,(1980),‘RecherchesThéoriquesetExpérimentalessurlesMouvementsdesVéhiculesFerroviairesCirculantàuneVitessede200km/hetExigencesRelativesàl’EntretiendesLignesàGrandeVitesse’,RailInternational.

267.ORE,C138,RP5(1980),EffectofTrainSpeedonthePermissibleMaximumValueofLoadΣY=SfromthePointofViewofTrackDisplacement,Utrecht.

268.ORE,D117,RP8(1976),InfluenceofVariousMeasuresattheLateralResistanceofanUnloadedTrack,Utrecht.

269.SauvageR.,AmansF.,(1969),‘RailwayTrackStabilityinRelationtoTransverseStressesexertedbyRollingStock-ATheoreticalStudyofTrackBehavior’,RailInternational,November1969.

CHAPTER14270.KocW.,(2012),‘DesignofRail-TrackGeometricSystemsbySatellite

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Routes’,AREA,Washington.272.ClaverieG.,CrosazY.,(2002),‘L’InsertionPaysagèredelaLigneNouvelle

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281.UIC,(2004),MaximumPermissibleWearProfilesforSwitches,May2004.282.ButzbacherWeichenbauGesellschaft(BWG),(2004),Switches,Crossings

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284.UIC,711R,(1990),GeometryofPointsandCrossingswithUICRailsPermittingSpeedsof100km/hormoreontheDivergingTrack,Paris.

285.BourdaA.,(1991),‘UnSystèmed’InformationpourlesPostesd’AiguillageetdeCirculation’,RGCF,Jan.1991.

286.DeutscheBundesbahn(1988),MerkblattfürdenEntwurfvonGleisanschlüssen,Frankfurt.

287.ORE,C138,RP8,(1984),PermissibleMaximumValuesfortheY-andQ-ForcesandDerailmentCriteria,Utrecht.

288.LuggP.,(1983),‘CrossingsandTurnouts’,TrackCourse,RIA,London.

CHAPTER16289.PlasserandTheurer,(2013),InformationMaterialforLaying,Tampingand

MaintenanceEquipmentoftheTrack,Vienna.290.Speno,(2013),TechnicalManualsforGrindingMachines,Geneva.291.TzanakakisK.,(2013),‘TheRailwayTrackanditsLongTermBehavior’,

Springer,Heidelberg.292.AndradeR.,TeixeiraF.,(2011),‘UncertaintyinRail-TrackGeometry

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294.ViletteFr.,(2005),‘EvolutiondelaTélésurveillancedesInfrastructuresFerroviaires’,RGCF,No135.

295.OnoSh.,NamakuraA.,OdakaT.,(2003),‘High-speedTrackInspectionTechnologies’,JPEast,TechnicalRevue,No2.

296.DermenghemJ.-P.,BimainA.,ViletteFr.,(2002),‘LaMaintenancedel’InfrastructuredesLignesàGrandeVitesse’,RGCF,No108.

297.UIC,(1992),FactorsaffectingTrackMaintenanceCostsandtheirRelativeImportance,Paris.

298.ProfillidisV.,(1986),‘BasicPrinciplesfortheTrackMaintenanceWorks’,TechnikaChronika(Scient.Bullet.ofGreekEngineers),Vol.6,No3,Athens.

299.UIC,(1986),LayingandMaintenanceofTrackmadeupofContinuousWeldedRails,Paris.

300.LewisR.,(1983),‘TrackRecordingMachines’,TrackCourse,RIA,London.

301.ORE,C9,RP9,(1983),‘TolérancesenServiceAdmisesdanslaSuper-structuredelaVoieenRelationavecsonEtatetlaMarchedesVéhicules’,Utrecht.

302.WaghornD.W.,(1983),‘WeedControl’,TrackCourse,RIA,London.303.WilmottD.J.,(1983),‘NewTrackConstruction’,TrackCourse,RIA,

London.304.JaninG.,(1982),‘LaMaintenancedelaGéometriedelaVoie’,RGCF,June

1982.305.ORE,D117,RP2,RP7(1973),Etudedel’EvolutionduNivellementen

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307.Shao-TangYen,Ying-HaurLee,(2007),‘ParameterIdentificationandAnalysisofaSlabTrackSystemusing3DAbacusProgram’,ASCE,Journ.ofTransp.Eng.,Vol.133,No5.

308.LayE.,AblingerP.,(2002),‘FesteFahrbahnKöln-Rhein/Main:EinerichtigeEntscheidung’,Eisenbahningenieur,Vol.53,No12.

309.EsveldC.,(1997),‘Low-MaintenanceBallastlessTrackStructures’,RailEngineeringInternational,No3.

310.DarrE.,FierbigW.,(1996),‘StandderEntwicklungunddesEinbahnsderFestenFahrbahn’,ZEVGlasersAnnalen,Vol120,No4.

311.HennW.D.,(1992),‘SystemComparisonBallastedTrack-SlabTrack’,RailEngineeringInternational,No2.

312.ProfillidisV.,PoniridisP.,(1990),‘NonlinearAnalysisofaSlabTrackrunbyMetro’,ScientificJournaloftheGreekLaboratoryofPublicWorks,Vol.105-106.

313.BrownJ.,(1983),‘ContinuousSlabTrack’,TrackCourse,RIA,London.314.SauvageR.,ErrieauJ.,(1970),‘LesPosesdeVoiesansBallast’,RGCF,

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CHAPTER18315.RohitSharmaetal.,(2012),‘AutomaticBrakingSystemforTrainsUsing

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l’Avancementd’unTrainàGrandeVitesse’,RGCF,December2002.317.AndréD.,(2002),‘AérodynamiquedanslesTunnelsduTGV

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319.TsujimuraT.,TakaoK.,SatoK.,(1993),‘RecentTrendsofBrakeDiscMaterials’,JapanRail.Eng.,Vol.32,No3.

320.ABB,(1992),TractionVehicleTechnicforAllApplications,Mannheim.321.LacôteF.,(1992),‘TheLimitsoftheWheel-RailContactSystem’,Rail

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322.ORE,C179,RP1,(1990),ApplicabilityofComputationalFluidDynamicstoRailwayAerodynamicProblems,Utrecht.

323.BoiteuxM.,(1990),‘InfluencedelaVitesseetdesdifférentsParamètresConstructifssurl’AdhérenceenFreinage’,RGCF,July-August1990.

324.MetzlerJ.-M.,(1989),GénéralitéssurlaTraction,ENPC,Paris.325.SNCF,(1988),‘LaDynamiqueduMouvementdesTrains’,Paris.326.WendeD.,(1983),Fahrdynamik,TranspressVEBVerlagfür

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l’avancementdesMatérielsRoulants,SNCFEditions.331.ORE,QuestionB44,(1966),AdhérencedesLocomotivessousl’Anglede

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333.EuropeanCommission,(2011),‘TechnicalSpecificationforInteroperabilityrelatingtotheRollingStockSubsystem’,EC2737/2011,Brussels.

334.VionnetR.,PouillartTh.,VietJ.,(2005),‘DéterminationdesContraintesRésiduellesparUltrasonsdanslesRouesàlaSNCF’,RGCF,May2005.

335.EngelE.,(2004),‘AccesstoStationsandTrainsfortheMobility-impaired’,RailInternational,January2004.

336.UICCode510-2,(2004),‘TrailingStock–ConditionsConcerningtheUseofWheelsofvariousDiameterswithRunningGearofDifferentTypes’,Paris.

337.StevenotG.,DemillyF.,(2002),‘LesPossibilitésd’AméliorationdelaDuréedeViedesRouesdeChemindeFer’,RGCF,May2002.

338.ProfillidisV.,(2001),‘TiltingTrains-OperationalCharacteristicsandImpactonTravelTime’,PublicTransportInternational,Vol.1.

339.ProfillidisV.,(1998),‘ASurveyofOperationalTechnical,andEconomicCharacteristicsofTiltingTrains,RailEngineeringInternational,Vol.2.

340.RaisonJ.,(1998),‘LesEquipementsdeFreindesRamesTGV’,RGCF,March1998.

341.OkamotoI.,(1998),‘HowBogiesWork’,JapanRailwayandTransportReview,Vol.18,December1998.

342.YamanakaT.,(1995),‘VehicleDesignConceptTowards21stCentury’,JapanRailEng.,Vol.32,No4.

343.JolyR.,(1988),‘Circulationd’unVéhiculeFerroviaireenAlignementetenCourbe-BogieàEssieuxAuto-Orientés’,RailInternational,April1988.

344.UIC,Fiche510-5,(1988),HomologationTechniquedesRouesMonoblocs,Paris.

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346.PagèsM.,CourtoisCh.,(2005),‘L’AlimentationElectriquedelaLGVEstEuropéenne’,RGCF,July.–Aug.2005.

347.RGCF,TractionElectrique,December2004.348.UIC,Code600OR,(2003),ElectricTractionwithAerialContactLine,

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352.LacôteF.,(1998),‘LesMutationsduMatérieletdelaTractionauXXSiècle’,RGCF,July-Aug.1998.

353.GigchV.,DuinV.,HeijskerV.,(1996),‘SizingtheTractionPowerSupplySystemwiththeAidofProbabilityTheory’,RailInternational,Jan.1996.

354.KobayaskiT.,Ikeda,K.,(1994),‘DevelopmentofNewTypesofContactWireforHigh-SpeedTrainonShinkansen’,Japan.Rail.Eng.,Vol.34,Tokyo.

355.KöckF.,(1990),‘FahrzeugdiagnosederICE–TriebkopfeundandererHochgeschwindigkeitsfahrzeuge’,ETR,No6.

356.MetzlerJ.-M.,(1990),LaTractionElectrique,ENPC.

357.JutardM.,FitaireM.,LeDucE.,(1989),‘Moyensd’EtudedesArcsdeRuptureduContactPantographe-Caténaire’,RGCF,November1989.

358.UIC,Leaflet606-2,(1986),Installationof25kVand50HzOverheadContactLines,Paris.

359.SuddardsA.D.,(1983),‘Electrification,ConstructionandInstallation’,TrackCourse,RIA,London.

360.OliverosRivesF.,RodriguezMendezM.,MegiaPuenteM.,(1983),TratadodeExplotacióndeFerrocarriles,EditorialRueda,Madrid.

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362.WungJun-Feng,(2011),‘NewTrainControlSystemsSuitableforTrainswithSpeedsupto350km/h’,ASCE,Journ.ofTransp.Eng.,Vol.137,No5.

363.UIC,Code762R,(2005),SafetyMeasurestobetakenatLevelCrossingsonLinesoperatedfrom120km/hto200km/h,Paris.

364.VinoisJ.-A.,(2004),‘ERTMS,uneOpportunitésansPrécédentpourConcrétiserl’InteropérabilitéduRéseauFerroviaireCommunautaire’,RGCF,May2004.

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Abbreviations

AC–DC Alternating–DirectcurrentAmtrak AmericanTrainCompanyASCE AmericanSocietyofCivilEngineersb Non-compensatedcentrifugalaccelerationBR (former)BritishRailwaysCBR CaliforniaBearingRatiodB DecibelDB GermanrailwaysE ModulusofelasticityECMT EuropeanConferenceofMinistersofTransportERA EuropeanRailwayAgencyERRI EuropeanRailResearchInstituteERTMS EuropeanRailTrafficManagementSystemEU EuropeanUnionGDP GrossDomesticProductGPS GlobalPositioningSystemhd/he Cantdeficiency/Cantexcess

HST High-SpeedTrainICE Germanhigh-speedtrainIRR InternalRateofReturnITF InternationalTransportForumJR JapaneseRailwaysM Bendingmoment

Maglev MagneticlevitationtrainN LoadingcyclesNPV NetPresentValueOECD OrganizationforEconomicCooperationandDevelopmentORE OrganismedesRecherchesetd’EssaisPPP Public-PrivatePartnershipQ AxleloadR Radiusofcurvature(horizontal)orrunningresistancer SpecificresistanceR 2CoefficientofdeterminationRENFE SpanishrailwaysRo-Ro Rollon-RolloffRv Radiusofcurvature(vertical)

S1 Subgradeofpoorquality

S2 Subgradeofmediumquality

S3 Subgradeofgoodquality

SNCF FrenchrailwaysT TrafficloadTGV Frenchhigh-speedtrainTOC TransportOperatingCompanyTSIs TechnicalSpecificationsforInteroperabilityUIC InternationalUnionofRailwaysUK UnitedKingdomY TransverseforceZ TractionforceNumericalrangesinthisbookareindicatedwiththe‘÷’symboltoavoidconfusionwiththeminus‘-’symbol.

Index

Allindexentriesshownherecorrespondtothepagenumberswithintheprintededitiononly.Withinthisdigitalformatthesepagenumbersallowforcrossreferencingonly.

AASHOclassificationofsoils202Abacussoftware180ABB44,409,438accelerationoftrain396accelerometer224accessibility152accident459,474adaptability46,48,119,130additionaldynamicloads170,189adhesioncoefficient394,395adhesionforce393Adinasoftware180advantages(ofrailways)44advertising117aerotrain3,39Airbus24,95airpollution6,100,463airresistance382,383airtransport21,32,51,140airports21,22alignment316÷330Alstom24,409,438alternatingcurrent15,000V,16⅔Hz423alternatingcurrent25,000V,50Hz423Amtrak63,98,151

anti-skiddevices398asphalt202,372,379ASTMclassificationofsoils202asynchronousmotor437,438environmentalpollution6,463audiblesignals442Australia4,8,12,16,66,151,157,169,225,261,264,268,269,458Austria12,16,18,48,58,109,110,111,112,113,204,230,232,264,330,423,

456,462AVEtrain410axle404,405axleload158,293azobé261

balisetransmissionmodule457ballast,coefficient173

Devaltest289,290fatigue287fineparticles285,286fines285flakinessindex285functions282granulometriccomposition283hardness289÷292lifetime97,301LosAngelestest206,290,291,292mechanicalbehavior287,288Microdevaltest291modulusofelasticity184,288re-use301strengthandhardness291stress–strainrelationship287thickness293÷297

ballastedvs.non-ballastedtrack156,157,372,380baseplate155,156,278,279bearingcapacity201,293,366,372

Belgium16,27,28,34,47,48,109,110÷112,230,264,456bendingmoment176,177benefitsfromarailproject126blocksection445bogie171,187,188,311,313,382,384,391,406

articulated407componentsof407non-articulated406self-steering407

Bögltechnique377,378Bombardier24,409boundaryelement172Boussinesq172,174,175,178,298Box-Jenkins82brakeshoe397,468brakingdistance398÷400,441brakingpercentage399brakingdistanceathighspeeds400Brazil5,16,28,169,264,458bridge23,54,91,92,97,109,133,158,174,193,223,224,257,309,316,333,

335,350,432,468,475broadgaugetracks158,231,232,268,318,386buffer408Build–Operate–Transfer(BOT)128Build–Own–Lease–Transfer(BOLT)128Build–Own–Operate(BOO)128Build–Own–Operate–Transfer(BOOT)128Build–Transfer–Operate(BTO)128bullheadrail225,226bus2,9,10,11,12,15,18,25,72,78,79,101,140BusinessPlan130,131businessunit122

cabsignaling440,457Canada4,5,8,12,52,63,64,87,264,268,269cantapplied318,322

cantdeficiency319,322cantexcess319,322canttheoretical319cantvalues322capacityoftrack18,454,455,457carbon227,228,259,463,464carbontax464carbondioxide6,100,463,464carryingcapacity18,457Casagrande202,203,207catchmentarea218catenary36,431CBR202,207ChannelTunnel37,38,377

forecastofdemand76geotechnicalanalysis201

charges,infrastructure55,106÷113,136checkrail339,340chemicalcomposition,rail227China4,5,8,9,10,11,12,13,16,24,27,28,31,34,36,53,65,225,235,268,

269,373,458,471chlorate222circulararc317,324,325clampingforce276,277classificationoflines161classificationofsoils202,203classificationofsubgrade205,206climatechange460closingofaline121,161clothoid317coefficientofdetermination75cohesion,valuesof184colinearity77combinedtransport18,19,49,70,98,107commercialorientation147compaction207

competition3,4,18,20,21,22,44,45,49,50,51,52,61,63,64,65,66,115,121,123,124,139,143,148

complementarity20compressivestrength184ComputerAidedDesign(CAD)334concretesleeper263÷272

manufacturing270,271qualitycontrol270types264

conductorrail420,421,432congestion18,100,101,478conicaltread161,162,164,165Conrail63constitutivelaw179,180,181consumptionfortransport462contactsurfaces195contactwire,cross-section422contestability51continuousweldedrail(cwr)252÷257

distressing256forces253,254mechanicalanalysis253

corrugations246Cosmossoftware180cost,accidents100,101,474

airpollution100,101,102aircrafts95ballast302climatechanges100,101,102combinedtransport19congestion100,101,102,478constructionoftrack91÷94definition88electrification424external89generalized90

inrelationtodistance18infrastructure,maintenance88,94infrastructure,operation95marginalexternal101,102marginalsocial89marginal88,89noise100,101,102,470offorecast86offuel5,463,473operation,freight98,99operation,passengers97,98rollingstock95,96slabtrack380

cost-benefitmethod126coupling408creep161,163,170,278Crocodile,speedcontrol452crosssubsidy55cross-elasticity115crossings338,341,345cross-sectionsoftrack297÷301cubicparabola317,324customersatisfaction142cutsection215

dangerousgoods476deadmean’shandle451debt49,50,52,64,65,122,148debtcrisis49,122decelerationoftrain396decibel192÷194,470defect,acceptancevalues359,360

alertvalues358emergencyvalues359,361horizontal356,359,360,361,364interventionvalues359,360

limitvalues358÷362longitudinal355,359,360,361rateofprogress362,363recordingmethods357,358transverse355,359,360,362,364

deficit3,46,49,103,106,116,124,137,139,148Delphimethod71demand34,38,69,70depot439derailment310÷314,345

duetotrackshifting310,313duetotransversewinds314duetovehicleoverturning312duetowheelclimbingonrail311,313,345

deregulation45,60,62,63designoftrack190,191,296,297Devaltest289,290DeveloperFinancing128development,economic7diagnostictests77diesel–electriclocomotive419diesellocomotive419,420,426dieseltraction418dieselvs.electrictraction420,426differentialsettlement156,373dimensioningoftrack280,281directcurrent750V,1,500V,3,000V422,423,424,425directcurrentvs.alternatingcurrent424Directive12/200155Directive13/200155Directive14/200155Directive440/199155discbrake,stressesin398distanceoftrackaxes36,167,297÷301distributionoftrainloadtosleepers186distributionoftrainloadtotracklayers156,185

divertedtraffic91Dormon’srule208double-headedrail225drainage204,218drivers,trainingandcertification56,459Drucker-Pragercriterion181dynamicanalysis170,186÷188dynamicimpactfactor189,190

earthquake224econometricmodel77,78,87economiccycles3Eisenmann’stheory236elasticbehavior181elasticfastenings273÷276elasticline,slabtrack375

sleeper187,267,270elasticity,modulus184,207elasticityofdemand96elastoplastic181electricarcwelding256electriclocomotive426electriclocomotive,maintenance439electricmotor419electrictraction420÷438

alternatingcurrent423,424,435directcurrent422,436overheadcontactwire420,421,428÷432powersupply420,421substations420,421,422systemsinEurope424technicalcharacteristics425

electricalinsulations278electrification133,168,420÷438

powerandelectricalcharacteristics433whensuggested427,428

electrificationcost94,424electronicticketing122embankmentsection215energy4,5,469÷474energyconsumption469÷473energyconsumptionperkilometer428,433,471entrants51,143entrepreneurial144environmentalaesthetics337environmentalaspectsoflayout337environmentaleffectsofrailways460÷478ergonomy409Eurobalise456EuropeanRailResearchInstitute(ERRI)23,207EuropeanRailTrafficManagementSystem(ERTMS)456÷458EuropeanRailwayAgency(ERA)23,56Europeanstandardizationofrailprofiles228,229EuropeanUnion6,7,8,9,10,11,12,14,23,54,55,56,58,59,71,98,106,

139,458Eurostar37,76,117,410,438evaluationofaproject124expansiondevice256expansionzone254expertsystem358externalenvironment119,121,130

fastening273÷277anchorage277clampingforce277design277elastic273÷275elongation276,277functions273rigid273types274

fatigue158,212,239,245,252,263,287

ballast287rail239÷242subgrade212

feasibilityanalysis,electrification426,427feasibilitystudy124÷126,334filter204,220,221finaldesignofatrack336financingarailproject126÷129Finland108,110,111,112,113,264,456finiteelementmethod172,178÷180,375,398,430,431geotextiles221

limitconditions180mesh179rail194,195slabtrack375stressvalues185track179verticalsettlements185

fire39fishplates251flakinessindex285flash-buttwelding255forecastofdemand67÷87formationlayer154,207,208,209formationrehabilitation209,366Foucaultcurrent226foulingdistance340Fouriertransform175,176fracturemechanics242fractureofwindowglass389France2,6,8,10,12,13,16,27,28,34,36,40,47,57,58,62,92,95,107,110,

111,112,116,136,167,252,264,283,290,291,292,298,302,322,323,324,330,377,380,382,383,384,399,414,422,438,452,456

frequencyofmaintenanceworks211,353,368,373frequentuseprograms117frictionangle182

frogangle339,340frost204,213,214,215

index213protectionthickness213,214

fuzzymodels80÷82

‘gateturnoff’technique436gasturbinelocomotives417gaugeoftrack157,158,360GDP6,78,101,462GeneralElectric24generalizedcost80,87,90,124generateddemand34geologicalmap199geophysicalmethods199geotechnicalclassifications202,203geotechnicalstudy198÷201geotextile204,219÷222,294Germany2,8,10,12,13,16,27,34,35,36,40,41,47,48,58,59,62,92,95,

107,108,110,111,112,142,148,167,202,230,250,251,256,264,268,269,270,279,284,300,302,322,323,330,373,376,386,399,410,423,428,452,456

GIS25globalwarming460globalization3,7,45,48GPS25,411gradientoflongitudinalprofile29,36,331÷333granulometriccurve203,283Graphersoftware75gravel(seesubballast)gravitymodel79Greece1,16,78,264greenhouseeffect463grindingofrails246,367,468,470groovedrail225groundvibration187,188,191÷194,470

groundwaterlevel204GSM410,440gyroscope412

handicapsofrailways44hardening240hardness228,289HarvardGraphicssoftware75hazardousmaterial,transport476health135,146,192herbicides222,223,371Hertz161,162,233heteroscedasticity77highspeeds2,26÷39,76,91,92,323,358,400,433,434

powersupply36,433rollingstock36,433technicalcharacteristics36,323,410,433trackrequirements35,323,360,433turnouts347

highwayengineering197,208Hillcriterion181holdingcompany53,58,59,61horizontaldefect356,358÷362humanresources51,144÷147hydrauliccalculations217÷219hydraulicdevice204hydrogeologicalconditions203

ICE24,95,323,410,438India5,8,9,10,11,12,14,16,28,53,65,157,169,235,264,268,269,422,

456,458,471Indusi,speedcontrol456inertialresistance391,392informaticstechnologies(IT)141infrastructure,assets104

charges111,112

definition54pricing103÷113

INRailsoftware334integratedmodel57interlock,singletrack,450approach450inter-modal50,53,121,123internalenvironment119,121InternalRateofReturn126internet3,45,76,141,145interoperability2,23,24,25,48,55,56,138,455÷458

definition455powersupply456signaling456÷458trackgauge455

intra-modal4,49,53,115,121,122,139Iran5,12,16,28ISO123Italy8,10,12,13,16,27,28,34,36,39,47,48,52,92,99,108,109,110,111,

112,113,136,202,230,252,264,268,269,320,323,373,414,422,456,462

Japan4,8,9,10,11,12,13,14,15,16,26,27,28,34,35,36,40,41,42,43,52,53,64,65,98,148,156,157,161,167,169,193,237,264,268,269,270,298,301,328,373,375,377,380,412

jerkoftrain397

Kalker161Kelvin-Voigth187kinematics164Korea4,12,24,27,28,34,36,42,92,115,373,410Krupp438

laborlegislation145,147landoccupancy477,478lateraltrackresistance304

layingthetrack351,352layout316÷337layoutformetrictracks333LeShuttle37Lease–Rehabilitate–Operate(LRO)128LeastMedianofSquares(LMS)83levelcrossings458,459,475liberalization45,49,56,139licensecertificate55,56lifestyle142,478lightsignaling,definition443lightsignaling,partsof446,447lightsignals447lighting54linearprogramming145linearity170Linelocfastening275loadinggauge,American167

British166definition165dynamic168European165,166highspeeds167metrictrack168,169metro168static165tunnel168

localoperatingboard448locomotive-trackcommunication453logistics20,143longitudinaldefect355,359÷362longitudinalforce169long-termforecasts77,82,86Long-TermLease128LosAngelestest206,290,291,292low-costairtransport21,122

magneticfield42magneticlevitation(maglev)2,40÷42maintenancecoefficient210÷212maintenanceoftrack353÷370

equipment365,366,367intervalbetweensessions363

Maison’sformula398management,freighttransport142,143

infrastructure136÷138passengertransport138÷142

manganese227,228marketsurvey70÷73marketing117,122,142marshallingyard54,133,342MasterPlan130,131mathematicaloptimization145mathematicalpointofturnout339maximumvs.minimumspeed329

mechanicalbehavior,ballast184,185,287rail194,195slabtrack374sleeper184,185,187,270subgrade184,185,212

mechanicalcharacteristicsoftrackmaterials184,207medium-termforecast82,86metricgaugetracks157,169,231,232,296,318,330metro18,153,168,402,417,454Mexico63,264,458Microdevaltest291Microfitsoftware75MicrosoftExcelsoftware75MicrosoftProject352Miner’srule240MITclassificationofsoils203mobility6model,definition67,68

econometric77,78fuzzy80÷82gravity79statistical74,81

modulusofelasticity184,207moisturecontent206monoblocksleeper266÷270

bendingmoments269deformability270geometricalcharacteristics268lifetime97,270mechanicalstrength268,269stresses185,269

multi-criteriaanalysis126MXRailsoftware334

Nablafastening274,275,280Nadal’sformula311,345narrowtrack(seemetricgauge)nationalization3NetPresentValue125Netherlands16,27,28,34,48,59,94,109,110,111,112,142,264,360,373,

376,456,462,477networkanalysis145NetworkRail60,150newentrants51,65,143NewZealand66,157nitrousoxides463noise191,192,193,466÷469

barriers194,469,470inhighspeeds193,194inrelationtodistance193methodsofreduction470

non-ballastedtrack157,372,373,375non-compensatedacceleration319,320,322,343non-linearity170

Norway16,98,110,111,112,230,264,423,452

Odossoftware334oilprice5,473oilreserves5,461,471OperatingControlCenter411,436ordinatesofcubicparabola324ordinatesofverticaltransition331organicsoils206OrganismedesRecherchesetd’Essais(ORE)23,207,242,287organizationstructure120,121organizationaldecision121outlinedesign335outsourcing137,138,143,147,371overheadcontactwire420,421,428÷432

cross-section430displacement431electricalcharacteristics430finiteelementmodel430forcesdeveloped431mechanicalcharacteristics430oscillation431physicalmodel429,430suspensionmethods431voltage430,431

overmanning144ozon463

pads155,156,278,279forces279functions278materials279thickness278

Pandrolfastening275,281pantograph36,432÷434paraboliccriterion182

pathallocation55,56,57Pedeluckformula399Pendolino412photoelasticity239piezometriclevel201Plasser365,366plasticitycriterion181plasticityindex205,206plateloadtest199,200Poisson’sratio184Poland8,16,28,48,110,111,112,113,230,264,456polessupportingoverheadline434populationconcentrations31Portugal8,16,28,29,48,109,110,111,112,264,456,462post-tensionedsleepers268,269power,requiredoftrain395,396preliminarydesign334,335prestressed-concretesleeper266÷270prestressingtendons270pre-tensionedsleepers268,269priceelasticity114pricing103÷118primarysuspension171,406Primaverasoftware352privatecarownership7,29privatization43,45,50,56,60÷62,147÷151

andcompetition124effects150ofinfrastructure149ofoperation149,150somecases150targets147

Proctortest209productivity15,16,62,145profit147,148project131

projectmanagement131÷135caseofahighspeedline134cost132development134execution135organization134scope132whensuggested133

publicserviceobligations46,56,116,139,152Public–PrivatePartnerships(PPP)52,56,128punctuality69,70,143

qualitativemethodsofdemandforecast70÷73qualitycontrol123,135qualityofinfrastructure138questionnaire72,73

radiusofcurvature(layout)36,323,329radiusofverticaltransition331,332rail,broadgauge231,232

bullhead225chemicalcomposition227codificationofdefects243,244cracking243cross-section226,231,232,233defects242÷249fatiguestresses241,242fatigue158,239,240,241,242fracture242geometricalcharacteristicsofvariousprofiles234,235grades228,229grinding246,367grooved225hardness228,229horizontalcracking245

internaldiscontinuity242joints251lateralwear246lifetime97,250,251longitudinalverticalcracking245long-pitchcorrugation246manufacturing226,227mechanicalstrength226,227,228,229metaldisintegration247metricgauge231,232,233plasticstresses237profilechoice230profile225,226,230÷235reprofiling250shelling246,247short-pitchcorrugation246stresses233,236,237,238surfacedisintegration245tacheovale245transport233ultimatetensilestrength226÷228ultrasonicdetection245,246wear249,250weldingdefects248weldingtechniques255,256wheelcontact,stresses233

Railtrack58,150rail-wheelangle311reactioncoefficient173,174,178recordingtrackdefects357,358rectifier423recyclingofmaterials478regionality116,152regression76,77regulation123,124Regulator56,149

reinforcedsoil216,217relayoftrackcircuit446remotecontrol436,437remotemonitoringcontrol448,449reprofilingofwheel404resistance,duetoacceleration391

duetogravity391duetotrackcurves390duringtrainmotion381÷392

resonance170restructuringofrailways45retainingwall216revealedpreferencesurvey71Rhedaslabtrack375,376riskassessment477RNfastening274rollingresistance(seerunningresistance)rollingstock23,24,36,95,96,122,170,171,189,356,410,411,412

allovertheworld410design409forhighspeeds95,412industries24

Ro-Ro19runningresistance382÷389

aerodynamic382,383asafunctionofspeed383broadgaugetracks386,387comparisontrain–road390enginepowerrequired383intunnel388,389mechanical382,383metricgaugetracks386,387

run-offflow217÷219Russia5,8,9,10,11,12,13,14,16,24,27,28,158,159,231,232,264,268,

269,422,424,471

safety6,37,136,449,459,461,474atlevelcrossings458,459,476certificate55,56,459definition441,442,459howtoincrease459

sand154,203Sateba265satellites25,411satisfactionofcustomers141,142Scenariowritingmethod71schedulingoftrackworks352schedulingoftrains453,454Schrammformula190secondarysuspension171,406seismicity224self-steeringbogie407semaphoresignaling440,442sensitivityanalysis131separation,infrastructurefromoperation3,44,51,53,61,62settlements,rail,ballast,sleeper,subgrade185settlement,slabtrack375shareofrailways8÷14,139shear,stress236,241

wave191Shinkansen26,32,193,279,378short-termforecast86Siemens24,409signaling153,277,440÷443

mechanical442semaphore442

sitereconnaissance199slabtrack35,156,157,182,372÷380

Bögltechnique377,378cost380elasticline375embeddedrailtechnique377,378

evolution373mechanicalbehavior374onasphaltlayer379prefabricatedprestressed-concretetechnique377,378Rhedatechnique375,376settlements374Shinkansentechnique377,378Stedeftechnique377stresses374Züblintechnique375,376

sleeper154,185,186,187,258÷272choice258,259effectontransversetrackresistance308functions258

inclinationofrailonsleeper165monoblock266÷270spacing161,162,178steel259,260stressesdeveloping185,272,280timber260÷263twin-block264÷266types258

SMS141socialsecurity122Sofistiksoftware180soil154,198÷203soilinvestigation198SouthAfrica8,12,157,169,235,264,268,269slopes215spacing,betweensleepers161,178

betweentracks167,297÷301Spain6,8,10,11,16,24,27,28,34,36,39,47,92,95,110÷112,158,159,264,

270,320,323,422,456specific,poweroflocomotive396,426

resistance382,384tractionforce392,393

spectralanalysis170,172,189,357speedcontrol451÷453,456Speno367spring407,408spring,lengthvariation407,408sprungmasses170,171,189stabilization365StaggersAct63stakingtracklayout336standardpenetrationtest199,200startingforce392,393statedpreferencesurvey71staticanalysis170,172,173,183station133,136,141,330statisticalprojection74÷77steam2,415÷417

locomotive416traction415,416

steamvs.dieseltraction417Stedeftechnique377steelsleeper259,260

geometricalcharacteristics260lifetime260mechanicalstrength259

stiffness156,174,188,191stochasticmethod311,357,459stockrail339,340strategicdecision119,121stress,distributionintrack156

rail194,195sleeper,ballast,subgrade185underthesleeper272,280

stress–strainrelationship180,181subballast,elasticitymodulus288

fatigue288functions154,282

subgrade,carryingcapacity207categorySi207functions198impactofmaintenanceconditions210,211impactonballast294mechanicalcharacteristics184,207modulusofelasticity184,207ofgoodquality205plasticdeformation212,213protectionfromfrost213,214stresses185,208,211,212

subsidies45,54,55,59,148,150subsoilofthesubgrade154,207substation420,421,435÷437substationspacing421,422,423,433superelevation36,322superelevationramp327superstructure154suspension171,406Sweden8,16,28,39,43,48,53,59,108÷113,136,230,264,268,269,423,

320,423,456,462switch,automatic–manual349

controldevices447derailment345design350forms342functions,requirements339radius340,343,344

switchesandcrossings338÷349Switzerland1,10,16,18,28,99,101,102,107,109,110÷113,202,230,235,

302,323,330,417,423,456synchronousmotor437,438systemsanalysis119,120

tacheovale245tacticaldecision119,121

taildetector448Taiwan8,27,28,34Talgo412,413tampingmachine365,366tariff113

pricing,freight118infrastructure103÷113operation113,114passenger116÷118

TechnicalSpecificationsforInteroperability154,165,167,229,231,280,321,333,350,361,401,403,405,408,432,455,468

telecommunications153,424tensilestrength184TGV24,26,32,91,92,93,117,190,193,218,264,321,323,331,382,383,

396,414,438Thalys410thermittwelding255Theurer365,366thyristor435,436Thyssen234tie154,185,186,187,258÷272(seealsosleeper)tiltingtrains39,120,319,

411÷414activemethod412additionalsuperelevation413angleoftilting413cost414curvedetection412loadgauge414axleload413maximumspeed413mechanismoftilting413passivemethod412reductionoftraveltimes414signaling414speedinrelationtoradiusofcurvature413trackcharacteristics414

whenused412tiltingtrainvs.highspeedtrain39,412,414timbersleeper260÷263

deformability187,263geometricalcharacteristics261,262lifetime263

timespentfortravel409time-seriesmodels82÷84TOCs60,61,150tonnage159track,definition153,154trackaccesscharges106÷113trackcircuit,definition443

howitoperates444relay444types443,444

trackcross-sections297÷301trackdefects353,355,356,358÷362trackgauge157,158,360trackindex173trackmaintenance352-368tracksettlements185,332trackstiffness173traction153,415÷439tractionforce392,393traffic,commuting18,139

freight12÷16highspeed34inrelationtodistance11intercity139international140passenger8,9,10,11,16regional139regularity441regulation441urban18,139

trafficload159,293trainintegritydetector447trainresistance382÷392trainspeedinrelationtoradiusofcurvature329,413tramway18,225,252,417transferstation141transitionbetweenballastedandslabtrack379,380transitioncurve,horizontally317,324

vertically330whennotused325

transportforwarders70transportmarket8÷16,130transverse,acceleration320

anchors310defect355,359,362,364dynamicforce304force169,303,304staticforces303trackresistance304winds314

transverseresistance,influenceofballastcompacting306,307influenceofballastcross-section305influenceofballastgranulometry305,306influenceofsleepertype308

traveltime32,33,69,478triporganization141truck2,13,14,18,19,37,143,143,463tunnel37,54,92,93,156,157,168,373,387÷390

crossingoftrains389cross-section389,390lateralopening389pressureproblems387runningresistance388,389

Turkey8,12,16,27,28,225,264,458,463turnout338÷350

automaticoperation349

components339,340derailmentcriterion345design350forhighspeeds347forms341,342geometricalcharacteristics344manualoperation348mathematicalpoint339maximumspeed343oncurvedmaintrack346runningspeed343tracklayout348,349

twin-blocksleeper,264÷266deformability267geometricalcharacteristics264,265lifetime97,266mechanicalstrength267

twistoftrack356,360,362,365

UIC22UIC,railprofiles226,232UIC,railgrades227ultrasonicrailinspection245,252unilateralcontact195,196,239,272UnitedKingdom4,8,9,10,13,16,27,28,34,37,39,48,50,53,60,63,64,

105,109,110,111,112,113,116,136,150,151,166,201,202,225,252,264,268,373,452,462,476,477

UnitedNations460unsprungmasses170,171,189UnitedStates3,4,8,9,10,11,12,13,14,15,16,17,19,21,25,27,28,29,30,

39,51,52,53,63,64,85,98,118,143,151,159,161,218,264,268,269,288,404,420,471,478

U-theilstatistics84

valueoftraveltime90,125,478vegetationonthetrack222,223,371

vehicle–trackinteraction171vehicledesign409velocity(seespeed)verticalforces169verticalsettlement185,375vibration171,191÷193Vignolesrail225viscoelastic187viscousbehavior171,188visualsignals442VonMisescriterion182Vosslohfastening274,275,280waitingtime141

water204,217÷220waves,pressure,shear,Rayleigh191wearofrail249,250wearofwheel403,404websites8,76,409weedcontrol222,371welding255,256wheel,defects404

diameter402,403geometricalcharacteristics403lifecycle404reprofiling404rim402,404stressesin404tire403

wheel-baseofavehicle405wheel-railcontact161,162,233windeffect314Wöhlercurve239woodensleeper(seetimbersleeper)worldevolution,prospects461

X2000train412

yieldmanagement117yieldstress183

Zimmerman175,178Züblintechnique376,377