Traffic Safety Fundamentals Handbook · 2016-09-16 · professionals in both government agencies...

Traffic Safety Fundamentals Handbook

Minnesota Department of TransportationOffice of Traffic, Safety and Technology

Revised June 2015Prepared by CH2M, Inc.

MnDOT Traffic Safety Fundamentals Handbook – IntroductionThe Minnesota Department of Transportation (MnDOT) published the original version of the Traffic Safety Fundamentals Handbook in 2001 and an updated version in 2008. Over 3,500 copies have since been distributed through MnDOT’s education and outreach efforts to practicing professionals in both government agencies and the private sector. In addition, the Handbook has been used as a resource in undergraduate and graduate traffic engineering classes at the University of Minnesota and is available to professionals in other states through the online posting on MnDOT’s website.

In the years since 2001, the field of traffic safety has witnessed a number of important changes. First, federal legislation (SAFETEA-LU) raised the level of importance of highway safety by making it a separate and distinct program and by increasing the level of funding dedicated to safety. In response to this legislation, the Federal Highway Administration (FHWA) provided implementation guidelines that required the states to prepare Strategic Highway Safety Plans (SHSPs) and encouraged their safety investments to be focused on low-cost stand-alone projects that can be proactively deployed across both state and local highway systems.

MnDOT initially prepared a Comprehensive Highway Safety Plan in 2004 and then completed updated Strategic Highway Safety Plans in 2007 and 2014. These documents included identification of a statewide safety goal, safety focus areas, and lists of high-priority safety strategies. These Plans also included key commitments intended to address FHWA’s safety objectives – adopting a long-term goal of achieving no traffic-related fatalities, a focus on reducing the most serious crashes, adding a new approach to the safety project development process that uses the results of systemic risk assessments to identify candidates for safety investment (in addition to the traditional site assessment approach used at high crash locations), dedicating a fraction of Highway Safety Improvement Program (HSIP) funds to improvements on local roadway systems, and increasing the level of engagement of local agencies in the statewide safety planning process. The key outcomes of these commitments include revising the priorities for HSIP, directing approximately 50% of HSIP funds toward implementing safety projects on the State’s local system of roadways, and completion of a project that was a first of its kind – the County Roadway Safety Plans (CRSPs). This project involved MnDOT providing

Traffic Safety Fundamentals Handbook – 2015 1

the technical assistance necessary to complete systemwide risk assessments and individual Safety Plans for each of Minnesota’s 87 counties. The county plans identified the priority crash types, a short list of effective, low-cost safety strategies, and the identification of the high-priority locations for HSIP investment. The CRSP project identified more than 17,000 safety projects, with an estimated implementation cost of approximately $246M.

As a result of these strategic safety planning efforts and the hard work of safety professionals in both state and local highway agencies, hundreds of highly effective safety projects have been implemented, and the results are impressive – Minnesota met the initial goal of achieving under 500 fatalities by 2008, and by 2011 the number fell to fewer than 400 fatalities. However, one fact remains constant – highway traffic fatalities are still the leading cause of death for Minnesotans under 35 years of age. This suggests there is still much work to do in order to move Minnesota Toward Zero Deaths.

This new edition of the Handbook has been updated to reflect new safety practices, policies, and research and is divided into four sections:

• Crash Characteristics – national and state crash totals, including the basic characteristics as a function of roadway classification, intersection control, roadway design, and access density.

• Safety Improvement Process – Site Analysis at High Crash Locations + Systemic Analysis = Comprehensive Safety Improvement Process.

• Traffic Safety Toolbox – identification of new tools (Highway Safety Manual and Crash Modification Clearinghouse) and an update on strategies, with an emphasis on effectiveness.

• Lessons Learned

For additional information regarding traffic safety, please contact either MnDOT’s Office of Traffic, Safety and Technology, State Traffic Safety Engineer (651) 234-7011 or Division of State Aid, State Aid Program Support Engineer (651) 366-3839.

Document Information and DisclaimerPrepared by: CH2M, Inc.

Authors: Howard Preston, PE, Veronica Richfield, and Nicole Farrington, PE

Funding: Provided by MnDOT Division of State Aid for Local Transportation

Published by: MnDOT Office of Traffic, Safety and Technology

The contents of this handbook reflect the views of the authors who are responsible for the facts and accuracy of the data presented. The contents do not necessarily reflect the views of policies of the Minnesota Department of Transportation at the time of the publication. This handbook does not constitute a standard, specification or regulation.


Table of ContentsCrash CharacteristicsA-2 Nationwide Historical Crash TrendsA-3 Upper Midwest Area 2013 Crash DataA-4 Fatality Rates of Surrounding States – 2013A-5 Minnesota Urban vs. Rural Crash ComparisonA-6 AASHTO’s Strategic Highway Safety Plan A-7 Role of Driver, Road, and VehicleA-8 Emergency Response Time Comparison A-9 Fatal Crashes are DifferentA-10 Minnesota’s Crash Mapping Analysis Tool (MnCMAT)A-12 Crash Involvement by Age and GenderA-13 Total Crashes by Road, Weather, and Lighting ConditionsA-14 Access vs. Mobility – The Functional Class ConceptA-15 Typical Functionally Classified Urban SystemA-16 Roadway Segment Crash Rates as a Function of Facility

Type and Access Density (MN) A-18 Intersection Crash Rates (MN) by Control Type and FamilyA-19 Intersection Crash Severity (MN) by Control Type and

FamilyA-20 Intersection Crash Distribution by Control Type and

Rural vs. UrbanA-21 Intersection Crashes – Severity vs. Frequency A-22 Roadway Segment Crash and Fatality Rates by

Jurisdictional ClassA-23 Roadway Segment Crash Rates Facility Type by Rural

vs. UrbanA-24 Roadway Segment Crash Distribution by Rural vs. Urban A-25 Segment Crashes – Severity vs. FrequencyA-26 Pedestrian/Bicycle Crash Distribution by Intersection

Control TypeA-27 Pedestrian/Bicycle Crash Distribution by Age

Safety Improvement Process B-2 Minnesota’s Strategic Highway Safety Plan (SHSP)B-3 Minnesota’s Safety Focus AreasB-4 Safety Focus Areas – Greater Minnesota vs. MetroB-5 Behavior Focus Area

– SpeedingB-6 – Impaired DrivingB-7 – Inattentive DrivingB-8 – Seat BeltsB-9 Infrastructure Focus Area

– IntersectionsB-10 – Lane DepartureB-11 Comprehensive Safety Improvement ProcessB-12 Why Have a Sustained High Crash Location

Identification Process?B-13 Alternative Methods for Identifying Potentially

Hazardous LocationsB-14 Effect of Random Distribution of CrashesB-15 Calculating Crash RatesB-16 Supplemental Analysis – More Detailed Record ReviewB-17 MnDOT’s Identification of At-Risk Trunk Highway

FacilitiesB-18 Systematic Analysis – State HighwaysB-19 Systematic Analysis – County HighwaysB-20 Systematic Analysis

– County Highway Crash Data for Greater MinnesotaB-21 – County Highway AssessmentB-22 – County Highway Crash Data for MetroB-23 – County Highway Assessment for MetroB-24 Implementation Guidance for State HighwaysB-25 Implementation Guidance for County HighwaysB-26 Safety Planning at the Local Level


Traffic Safety Tool Box C-2 Traffic Safety Tool Box – Then vs. NowC-4 Effectiveness of Safety StrategiesC-5 Safety Strategies

– HSIP Impact PyramidC-6 – CMF ClearinghouseC-8 – Highway Safety ManualC-10 – Highway Capacity ManualC-11 – Countermeasures that WorkC-12 – InfrastructureC-13 – BehaviorC-14 Roadside Safety InitiativesC-15 – Edge TreatmentsC-17 – Horizontal CurvesC-19 – Slope Design/Clear Recovery AreasC-20 – Upgrade Roadside HardwareC-21 Effectiveness of Roadside Safety InitiativesC-22 Addressing Head-On CollisionsC-24 Intersection Safety StrategiesC-25 Intersections

– Conflict Points – Traditional DesignC-26 – Conflict Points – New DesignC-28 – Enhanced Signs and MarkingsC-29 – Sight DistanceC-30 – Turn Lane DesignsC-31 – Roundabouts and Indirect TurnsC-32 – Traffic Signal OperationsC-33 – Red Light EnforcementC-35 Rural Intersections

– Safety Effects of Street LightingC-36 – Flashing BeaconsC-37 – Transverse Rumble Strips

Table of Contents

C-38 Pedestrian Safety StrategiesC-39 Pedestrian Safety

– Crash Rates vs. Crossing FeaturesC-40 – Curb Extensions and MediansC-41 Pedestrian/Bike StrategiesC-42 Complete StreetsC-43 Neighborhood Traffic Control MeasuresC-44 Speed ZoningC-46 Speed Reduction EffortsC-47 Speed Zoning – School ZonesC-48 Speed StrategiesC-49 Technology ApplicationsC-50 Impaired Driver StrategiesC-51 Inattention StrategiesC-52 Unbelted StrategiesC-53 Temporary Traffic Control ZonesC-55 Average Crash CostsC-56 Crash Reduction Benefit/ Cost (B/C) Ratio WorksheetC-57 Typical Benefit/Cost Ratios for Various Improvements

Lessons Learned D-2 Lessons Learned – Crash Characteristics D-3 Lessons Learned – Safety Improvement Process D-4 Lessons Learned – Traffic Safety Tool Box


Traffic Safety Fundamentals Handbook – 2015 A-1

Crash Characteristics

A-1

A-2 Nationwide Historical Crash Trends

A-3 Upper Midwest Area 2013 Crash Data

A-4 Fatality Rates of Surrounding States – 2013

A-5 Minnesota Urban vs. Rural Crash Comparison

A-6 AASHTO’s Strategic Highway Safety Plan

A-7 Role of Driver, Road, and Vehicle

A-8 Emergency Response Time Comparison

A-9 Fatal Crashes are Different

A-10 Minnesota’s Crash Mapping Analysis Tool (MnCMAT)

A-12 Crash Involvement by Age and Gender

A-13 Total Crashes by Road, Weather, and Lighting Conditions

A-14 Access vs. Mobility – The Functional Class Concept

A-15 Typical Functionally Classified Urban System

Section A

A-16 Roadway Segment Crash Rates as a Function of Facility Type and Access Density (MN)

A-18 Intersection Crash Rates (MN) by Control Type and Family

A-19 Intersection Crash Severity (MN) by Control Type and Family

A-20 Intersection Crash Distribution by Control Type and Rural vs. Urban

A-21 Intersection Crashes – Severity vs. Frequency

A-22 Roadway Segment Crash and Fatality Rates by Jurisdictional Class

A-23 Roadway Segment Crash Rates Facility Type by Rural vs. Urban

A-24 Roadway Segment Crash Distribution by Rural vs. Urban

A-25 Segment Crashes – Severity vs. Frequency

A-26 Pedestrian/Bicycle Crash Distribution by Intersection Control Type

A-27 Pedestrian/Bicycle Crash Distribution by Age

Traffic Safety Fundamentals Handbook – 2015

A-2

Highlights• Nationally,overthepast10yearstherehavebeenalmost55millioncrashes.

Overthatsametimeperiod,thenumberoffatalitieshasapproximatelydecreasedfrom42,000to32,000annually.

• Overthe10-yearperiod,exposure(VMT)hasincreasedonlyslightlyandhasbeenalmostflatduringthepast5years.

• Thelong-termtrendisfewercrashesandfatalitiesandarelativelyflatlevelofexposure.

1972 1979 1989 1999 2004 2007 2009 2012 2013CrashesTotal(thousand) N/A N/A 6,700 6,300 6,181 6,024 5,505 5,615 5,687

Fatal(thousand) N/A N/A 41 37 38 37 31 31 30

Injury(thousand) N/A N/A 2,153 2,026 1,862 1,711 1,517 1,634 1,591

PDO(thousand) N/A N/A 4,459 4,226 4,281 4,275 3,957 3,950 4,066

FatalitiesTotal 54,589* 51,093 45,582 41,717 42,836 41,259 33,883 33,561 32,719

TrafficRegisteredVehicles(million) 122 144 181 213 238 257 259 266 N/A

VMT(trillion) 1.3 1.5 2.1 2.7 3.0 3.0 3.0 3.0 3.0

RatesCrashes/100MVM N/A N/A 317 235 206 199 186 189 192

Fatalities/100MVM 4.3 3.3 2.2 1.5 1.4 1.4 1.1 1.1 1.1

Fatalitiespermillionregisteredvehicles 458 355 252 195 180 161 131 126 N/A

National Highway Traffic Safety Administration (NHTSA)*1972wastheworstyearforfatalitiesinU.S. VMT VehicleMilesTraveled100MVM 100MillionVehicleMiles

N/A NotAvailablePDO PropertyDamageOnly

Nationwide Historical Crash Trends

• Thedramaticdecreaseinthenumberoftrafficfatalities–24%overthe10-yearperiodbringstheannualnumberofdeaths(32,719)toalevelthatislowerthananytimeintheprevious60years.

• Thecombinationofdecreasingfatalitiesandaflatexposureresultsinafatalityrateof1.1,whichisa21%reductionandthelowestfatalityrateever.



Upper Midwest Area 2013 Crash Data

Highlights• Regionally,thereisawidevariationfromstateto

stateinboththetotalnumberofcrashes(16,000to120,000)andthenumberoffatalities(121to491).

• Minnesotahasaveragedapproximately75,000crashesandhasrecordedbetween357and455fatalitiesannuallysince2008.

• ThetrendinMinnesotaisfewercrashesandfatalities,inspiteofanincreaseinexposure(VMT).

• Minnesotahasbeenaleaderintheareaofhighwaysafety,withoneoftheloweststatewideaveragecrashandfatalityratescomparedtootherstatesinboththeregionandthenation.

• Thereisarelationshipbetweenthenumberoffatalcrashesandfatalities.Ingeneralacrosstheuppermidwestarea,theratiowas1.1fatalitiesperfatalcrash.

MinnesotaNorth Dakota

South Dakota Iowa Wisconsin

CrashesTotal 77,707 18,977 16,620 49,798 118,254

Fatal 357 133 121 290 491

Injury 21,960 3,901 3,921 13,091 28,747

PDO 55,390 14,943 12,578 36,417 89,016

FatalitiesTotal 387 148 135 317 527

TrafficRegisteredVehicles(million) 5.1 0.8 1.0 4.3 5.7

VMT(billion) 57.0 10.1 9.1 31.5 59.5

RatesCrashes/MVM 1.4 1.9 1.8 1.6 2.0

Fatalities/100MVM 0.7 1.5 1.5 1.0 0.9

Fatalities/MRV 76 184 134 75 93

CostsUSDollars(million)* $6,765 $2,063 $2,050 $4,853 $10,149

2013 Publications of MnDOT, NDDOT, SDDOT and IowaDOT

WisDOT data is preliminary

PDO PropertyDamageOnlyVMT VehicleMilesTraveledMRV MillionRegisteredVehicles100MVM 100MillionVehicleMiles

*EstimatedbasedondistributionofinjuriesandusingMnDOT2013crashcosts.


Fatality Rates of Surrounding States –2013

Highlights • Minnesotahasthelowestfatalityrateintheregionandconsis-

tentlyoneofthelowestfatalityratesinthenation.

• NationalFatalityRates

• Thenationalaverageis1.1for2013(2012disaggregatedrateswere1.9onruralroadwaysand0.8onurbanroadways)

• Trends:

− Lowestfatalityratesinthenortheast(mostlyurban)

− Individualstatefatalityratesrangedfrom0.6inMassachusettsto1.9inMontana

• Minnesota'soverallfatalityrateis0.7(1.1onruralroadwaysand0.4onurbanroadways).

• Nationwide,Minnesotahadthesecondlowestfatalityrate.Massachusettshasthelowestfatalityrateof0.6.

• Since1975,Minnesota’sfatalityratehasdroppedbyalmost77%.Thisdropisthelargestdeclineofanystate.

• TrafficfatalitiesarestilltheleadingcauseofdeathforMinnesotaresidentsunder35yearsofage.

• ThedatasuggesttherearesignificantopportunitiestomoveTowardZeroDeathsbyfocusingstatesafetyeffortsontheprimaryfactorsassociatedwithseverecrashes–inattention,alcohol,speeding,roadedges,andintersections.

National Highway Traffic Safety Administration (NHTSA)

Minnesota Nationally

Year Fatalities Fatality Rate Fatality Rate1975 754 2.9 3.4

1985 608 1.9 2.5

1995 597 1.4 1.7

2000 625 1.2 1.5

2005 559 1.0 1.5

2010 411 1.0 1.1

2012 395 0.7 1.1

2013 387 0.7 1.1


Minnesota Urban vs. Rural Crash Comparison

Highlights• Thetotalnumberofcrashesistypicallyafunctionof

exposure(VMT).

• InMinnesota,approximately40%oftheVMTisinurbanareasandapproximately60%ofthetotalnumberofstatewidecrashesareinurbanareas.

• However,77%ofthefatalcrashesinMinnesotaareinruralareas.

• Onaverage,ruralcrashestendtobemoreseverethanurbancrashes–thefatalityrateonruralroadsismorethan2.5timestherateinurbanareas.

• Thehigherseverityofruralcrashesappearstoberelatedtocrashtype,speed,andaccesstoemergencyservices.

MnDOT TIS, 2009-2013

“Rural”referstoanon-municipalareaandcitieswithapopulationlessthan5,000.

Total Crashes Fatal Crashes

Miles Vehicle Miles Traveled


AASHTO’s Strategic Highway Safety Plan

Highlights• Inthe1990s,AASHTOconcludedthathistoricalefforts

toaddresstrafficsafetywerenotsufficienttocauseacontinueddeclineintheannualnumberoftrafficfatalities.

• AASHTO’sStrategicHighwaySafetyPlanwasfirstpublishedin1997andthenupdatedin2004.

• Theplansuggestedsettinganewnational safety performance measure–thenumberoftrafficfatalitiesandsettingagoaltoreducethenation’shighwayfatalityratetonotmoretheonefatalityper100millionVMTby2008.

• The2004planintroducedinnovativeideas,including:

• SharedResponsibility–allroads,alllevelsofroadauthorities

• SafetyEmphasisAreas

• FocusonProvenStrategies

• ConsiderationofDriver,RoadwayandVehicleinter-actionswhenanalyzingcrashcausation

• DevelopmentofStateandLocalComprehensiveSafetyPlans


Persons Killed in Traffic Crashes

Note:2013fatalitiesfromFARSstatisticalprojections


Role of Driver, Road, and Vehicle

Highlights• Factorsthatcontributetoseriouscrashesinvolve

drivers,theroadway,andvehicles:

• Driverbehaviorsthatcontributetocrashesincludenotwearingasafetybelt,usingalcohol,beingdistracted,anddrivingaggressively.Driverbehaviorsareafactorin93%ofcrashes.

• Roadwayfeaturesincluderoadedges,curves,andintersections.Roadwayfeaturesareafactorin34%ofcrashes.

• Vehicleequipmentfailures,includingtireblowouts,towingtrailers,oversizeandloaddistribution.Vehiclefailuresareafactorin12%ofcrashes.

• StudieshaveshownthatsafetyprogramsthataddressmultiplefactorsofthefourSafetyE’s–Education,Enforcement,Engineering,andEmergencyServices–willbethemosteffective.

• ExamplesofeducationandenforcementprogramsincludetheDepartmentofPublicSafety’sProjectNightCap(alcohol)andCLICKITorTicket(safetybeltusage).The Role of Perceptual and Cognitive Filters in Observed Behavior, Kåre Rumar, 1985

Crash Causation Factors

Inthisexample,roadwaysarethesolecontributingfactorin3%ofcrashesandtheroadwayanddriverinteractionisthefactorin27%ofcrashes.


Highlights• ItappearsthatEmergencyResponsetimemay

beasignificantcontributingfactortothehigherfrequencyoffatalcrashesinruralareas.

• Nationally,responsetimesinruralareasaverage55minutesandarealmost45%longerthaninurbanareas.

• InMinnesota,theaverageruralresponsetimeis44minutes,whichisamongthelowestinthecountryandisthelowestresponsetimeinanystateintheupperMidwest.

• Thehigherfrequencyoffatalcrashesinruralareas,combinedwiththelongerEMSresponsetimes,hasledtodiscussionsinbothMinne-sotaandnationally,abouthowtobothreduceresponsetimesandtoimproveoutcomesfortheseriouslyinjured.InMinnesota,twotechniquesarewidelyusedtoaddressresponsetimes:theuseofAirAmbulanceinurbanareaswithlargenumbersofsignalsalongarterialcorridorsandEmergencyVehiclePreemptionoftrafficsignals.

• Minnesotahaswidelydistributedairambulancebaseswhichprovidecoveragetoallpartsofthestateandtransportcrashvictimsto15levelIandIItraumacenters.

Emergency Response Time ComparisonNational EMS Response Time

Levels 1 and 2 Trauma Centers

Timesareroundedtothenearestminute.

"Rural"referstoanon-municipalareaandcitieswithapopulationlessthan5,000.



Fatal Crashes Are Different

Highlights• Forthepast30years,theprimarysafetyperformancemeasure

wasthetotalnumberofcrashes.Thisprocessresultedinsafetyinvestmentsbeingfocusedonlocationswiththehighestnumberofcrashes,whichalsohavelargernumbersofthemostcommontypesofcrashes.

• ThemostcommontypesofcrashesinMinnesotaareRear-End(31%)andRightAngle(27%).Thesecrashesoccurmostfrequentlyatsignalizedintersectionsalongurban/suburbanarterials,whichbecamethefocusofsafetyinvestment.

• Oneproblemwithdirectingsafetyinvestmentstowardssignal-izedurban/suburbanintersectionsisthattherewaslittleeffectonreducingfatalities–onlyabout10%offatalcrashesoccurattheselocations.

• TheadventofMinnesota’sTowardZeroDeaths(TZD)programandthe2003adoptionofafatality-basedsafetyperformancemeasureledtoresearchthatfirstidentifiedthatfatalcrashesaredifferentfromotherlessseverecrashes.

• Fatalcrashesareoverrepresentedinruralareasandonthelocalroadsystem.ThemostcommontypesoffatalcrashesareRun-Off-Road(22%),RightAngle(12%),andHead-On(12%).

• ThesefactsaboutfatalcrasheshavechangedMnDOT’ssafetyinvestmentstrategies,whicharenowfocusedonroaddeparturesinruralareasandonlocalsystems.

Minnesota Crash Mapping Analysis Tool, 2009-2013


Minnesota’s Crash Mapping Analysis Tool (MnCMAT)

Highlights• Inordertoassistcitiesandcountiesingainingabetterunderstanding

ofcrashcharacteristicsontheirsystems,MnDOTStateAidforLocalTransportation,theMinnesotaLocalRoadResearchBoardandMinnesotaCountyEngineersAssociation(MCEA)havemadeanonlinetoolavailable-theMinnesotaCrashMappingAnalysisTool(MnCMAT).

• MnCMATisamap-basedcomputerapplicationthatprovides10yearsofcrashdataforallpublicroadsinMinnesota.

• Individualcrashesarelocatedspatiallybyreferencepointalongallroadwaysinthestate.

• Upto67piecesofinformationareprovidedforeachcrash,includingroute,location(referencepoint),date/day/time,severity,vehicleactions,crashcausation,weather,roadcharacteristics,anddrivercondition.

• Outputsthatcanbegeneratedfromtheapplicationforanalysispurposesincludemaps,crashdataexports,charts,andreports.

• Analystscanselectspecificintersectionsorroadwaysegmentsforstudy.Anoverviewoftheentirestate,MnDOTdistrict,county,city,ortribalgovernmentcanalsobegenerated.

• FormoreinformationaboutMnCMATandtoaccesstheonlineapplication,seewww.dot.state.mn.us/stateaid/crashmapping.html.

Minnesota Crash Mapping Analysis Tool


Highlights• Therecommendedanalyticalprocessforconductingasafety/

crashstudyistocompareactualconditionsataspecificlocation(intersectionorsegmentofhighway)comparedtoexpectedconditions(basedondocumentingtheaveragecharacteristicsforalargesystemofsimilarfacilities).

• MnCMATsupportsthisanalyticalprocessbyprovidingboththedataforindividuallocationsandforlargersystems–individualormultiplecounties.

• Thedatainthesegraphsindicatethatcrashesfortheselectedareapredominatelyoccurunderdaylightconditionsandamajorityarerear-endandrightanglecrashtypes.Additionally,thegraphsshowthedistributionofcrashesbyseverity.


Minnesota’s Crash Mapping Analysis Tool (MnCMAT)


Crash Involvement by Age and Gender

2013 Minnesota Motor Vehicle Crash Facts


Highlights• Thedistributionoffatalcrashesandtotalcrashesbyageindicatesthatyoung

peopleareoverrepresented.

• Minnesota’sStrategicHighwaySafetyPlanhasdocumentedthatyoungdrivers(under21yearsold)areinvolvedin24%offatalcrashes.Asaresult,addressingyoungdriversafetyissueshasbeenadoptedasoneofMinnesota’ssafetyfocusareas.

• Onestrategyhasbeenfoundtobeparticularlyeffectiveatreducingthecrashinvolvementrateofyoungdrivers–adoptionofacomprehensiveGraduatedDriversLicense(GDL)program.TheMinnesotaLegislaturetookastepinthisdirectionin2008byaddingprovisionsthatprohibitdrivingbetweenmidnightand5a.m.duringthefirst6monthsoflicensureandlimitingthenumberofunrelatedteenpassengersduringthefirst12monthsoflicensure.SinceadoptionofthismorecomprehensiveGDL,thenumberofseverecrashesinvolvingyoungdrivershasdroppedbyanaverageof13%peryear(comparedtoa4.5%peryeardropinallseverecrashes).

• Encouragingdrivereducationproviderstorequireaparenteducationcompo-nentisdemonstratingpromisingresultsinengagingparentstomoreeffectivelymonitorandcoachtheirteendriver.Educationprogramsincorporatingbothparentandteeneducationhelpparentsunderstandtheimportanceofteendrivingrestrictionstoreducedrivingriskasnovicedriversgainexperience.TheMinnesotaOfficeofTrafficSafety(OTS)developedthenationallyrecognizedPointofImpact:TeenDriverSafetyParentAwarenessProgramasacommunity-basedclassforparentsandtheirteendrivers.


Total Crashes by Road, Weather, and Lighting Conditions

Highlights• Someelementsoftrafficsafetyarecounterintuitive.Manypeople

thinkthatmostcrashesoccuratnightorduringbadweather.However,thedataclearlyindicatesthatcrashfrequencyisafunctionofexposure.Mostcrashesoccurduringthedayondryroadsingoodweatherconditions.

• Itshouldbenotedthatsomeresearch1haslookedatsafetyissuesduringnighttimehoursandduringsnowevents.Theresearchconcludesthattheconditionsrepresentasignificantsafetyriskbecauselowlevelofexposureresultsinveryhighcrashrates.

• Inaddition,thenewfocusonfatalcrashesreinforcestheconcernaboutnighttimehoursbeingmoreatrisk–approximately25%ofVMToccursduringhoursofdarkness,but31%offatalcrashes.

1MnDOTResearchReport1997-17,Table5.4,estimatedbasedonasamplefromMnDOT’sAutomaticRecordingStations.Minnesota Crash Mapping Analysis Tool, 2009-2013

All Crashes Fatal Crashes


Access vs. Mobility – The Functional Class Concept

Highlights• Oneofthekeyconceptsintransportationplanningdealswiththefunctionalclas-

sificationofaroadsystem.Thebasicpremiseisthattherearetwoprimaryroadwayfunctions–accessandmobility–andthatallroadwaysserveonefunctionortheother,orinsomecases,bothfunctions.

• ThefourcomponentsofmostfunctionallyclassifiedsystemsincludeLocalStreets,Collectors,MinorArterials,andPrincipalArterials.

• Theprimaryfunctionoflocalstreetsislandaccess,andtheprimaryfunctionofprincipalarterialsismovingtraffic.Collectorsandminorarterialsareusuallyrequiredtoservesomecombinationofaccessandmobilityfunctions.

• Keyreasonssupportingtheconceptofafunctionallyclassifiedsystemincludethefollowing:

• Itisgenerallyagreedthatsystemsthatincludetheappropriatebalanceofthefourtypesofroadwaysprovidethegreatestdegreeofsafetyandefficiency.

• Ittakesacombinationofvarioustypesofroadwaystomeettheneedsofthevariouslandusesfoundinmosturbanareasaroundthestate.

• Mostagenciescouldnotaffordasystemmadeupentirelyofprincipalarterials.Aregioncanbegridlockedifitisonlyservedbyasystemoflocalstreets.

• Roadwaysthatonlyserveonefunctionaregenerallysaferandtendtooperatemoreefficiently.Forexample,freewaysonlyservethemobilityfunctionandasagrouphavethelowestcrashratesandthehighestlevelofoperationalefficiency.

• Functionalclassificationcanbeusedtohelpprioritizeroadwayimprovements.

• Thedesignfeaturesandlevelofaccessforspecificroadwaysshouldbematchedtotheintendedfunctionofindividualroadways.

• Theappropriatebalancepointbetweenthecompetingfunctionsmustbedeterminedforeachroadwaybasedonananalysisofspecificoperational,safety,design,andlandfeatures.

FHWA Publication No. FHWA-RD-91-044 (Nov 1992)


Typical Functionally Classified Urban System

Highlights• Local Streets

• Lowvolumes(lessthan2KADT)

• Lowspeeds(30MPH)

• Shorttrips(lessthanonemile)

• Twolanes

• Frequentdrivewaysandintersections

• Unlimitedaccess

• 75%systemmileage/15%VMT

• Jurisdiction–CitiesandTownships

• Constructioncost:$250Kto$500K/mile

• Collectors

• Lowervolumes(1Kto8KADT)

• Lowerspeeds(30or35MPH)

• Shortertrips(1to2miles)

• Twoorthreelanes

• Frequentdriveways

• Intersectionsto1/8thmilespacing


• Jurisdiction–CitiesandCounties

• Constructioncost:$1Mto$2M/mile

ADT AverageDailyTrafficVMT VehicleMilesTraveledMPH MilesPerHour2K 2,0001M 1,000,000

FHWA Publication No. FHWA-RD-91-044 (Nov 1992)

• Minor Arterials

• Moderatevolumes(5Kto40KADT)

• Moderatespeeds(35to45MPH)

• Mediumlengthtrips(2to6miles)

• Three,four,orfivelanes

• Onlymajordriveways

• Intersectionsat1/4milespacing


• Jurisdiction–CountiesandMnDOT

• Constructioncost:$2.5Mto$7M/mile

• Principal Arterials

• Highvolumes(greaterthan20KADT)

• Highspeeds(greaterthan45MPH)

• Longertrips(morethan6miles)

• 4ormorelanes–accesscontrol

• Intersectionsat1/2milespacingandInterchanges1+milespacing


• Jurisdiction–MnDOT

• Constructioncost:$10Mto$50M/mile


Roadway Segment Crash Rates as a Function of Facility Type and Access Density (MN)

Highlights• Previoussafetyresearchgoingback30yearsindicatedapotentialrelationship

betweenaccessdensityandcrashrates.However,thisresearchdidnotaccountforotherfactorsthatareknowntoaffectcrashrates(ruralvs.urban,designtypeoffacility,etc.)andnoneofthedatawasfromMinnesota.

• Asaresult,in1998,MnDOTundertookacomprehensivereviewoftherelation-shipbetweenaccessandsafetyonMinnesota’sTrunkHighwaySystem.ThiseffortendedwiththepublicationofResearchReportNo.1998-27,“StatisticalRelation-shipBetweenVehicularCrashesandHighwayAccess.”

• Thesignificantresultsinclude:

• Documentingforthefirsttimetheactualaccessdensity(anaverageof8accesspermileinruralareasand28accesspermileinurbanareasalongStatehighways).

• Observingarelationshipbetweenaccessdensityandcrashratesin10of11categories.

• Identifyingastatisticallysignificanttendency(in5outof6categorieswithsufficientsamplesize)forsegmentswithhigheraccessdensitiestohavehighercrashratesinbothurbanandruralareas.


MnDOT Research Report 1998-27 “Statistical Relationship between Vehicular Crashes and Highway Access”


Roadway Segment Crash Rates as a Function of Facility Type and Access Density (MN)

Highlights• MnDOThascompletedtheprojectthatpreparedasafetyplanforeverycountyin

thestate.Oneofthefocusareasoftheplansinvolvedaddressingseverecrashesonruralcountyroadways.TheanalysisofMinnesota’scrashrecordsandtheresultsofasystemwideriskassessmentfoundacorrelationbetweenthedensityofaccessandcrashdensityalong27,000milesofruralcountyroadways.Thehigherthedensityofaccess,thehighertheaveragecrashdensity.

• Thesignificantresultsinclude:

• Documentingthattheaverageaccessdensityforcountyroadways(approximately8permile)issimilartorural,2-lanestatehighways.

• Observingarelationshipbetweenaccessdensityandcrashdensityinsegmentswithaboveaverageaccessdensitycrashesareover-representedandtheaveragecrashdensityincreasesasaccessdensityincreases.


Minnesota County Road Safety Plans, Data 2007-2011


Intersection Crash Rates (MN) by Control Type and Family

Highlights• Crashfrequencyatintersectionstendstobeafunctionofexposure–thevolume

oftraffictravelingthroughtheintersection.Asaresult,themostcommonlyusedintersectioncrashstatisticisthecrashrate–thenumberofcrashespermillionenteringvehicles(MEV).

• Crashfrequencyalsotendstobearesultofthetypeoftrafficcontrolattheintersection.Contrarytothepopularlyheldopinionthatincreasingtheamountofintersectioncontrolresultsinincreasedsafety,theaveragecrashrateatsignalizedintersections(0.5perMEV)ismorethan67%higherthanaveragecrashrateatstopsign-controlledintersections(0.3perMEV).Inaddition,theaverageseverityrateandtheaveragecrashdensityarealsogreaterforsignalizedcomparedtostopsigncontrolledintersections.

• Awealthofresearchalsosupportstheconclusionthattrafficsignalsarerarelysafetydevices.Mostbeforevs.afterstudiesoftrafficsignalinstallationsdocumentincreasesinthenumberandrateofcrashes,achangeinthedistributionofthetypeofcrashes,andamodestdecreaseinthefractionoffatalcrashes.

• Asaresultofcrashcharacteristicsassociatedwithsignalizedintersections,installingtrafficsignalsisNOToneofMinnesota’shighprioritysafetystrategies.

• Therearealsodatatosupportaconclusionthatsometypeofleftturnphasing(eitherexclusiveorexclusive/permitted),addressingclearanceintervalsandprovidingcoordinationhelpstominimizethenumberofcrashesatsignalizedintersections.

• ThecrashdatadocumentingcrashratesforintersectionsbytypeofcontrolwaspreviouslylimitedtotheStatehighwaysystem.However,completionoftheCountryRoadSafetyPlansincludedanalysisofalmost13,000intersectionsalongthecountysystem.TheresultsindicatethatintersectionsalongcountyroadshavecrashratesvirtuallyidenticaltosimilarintersectionsalongStatehighways.

2013 MnDOT Crash Data Toolkit, 2011-2013, and Minnesota County Road Safety Plans, Data 2007-2011


Intersection Crash Severity (MN) by Control Type and Family

Highlights• Thedistributionofintersectioncrashseverityappears

tobearesultofthetype/degreeofintersectioncontrolmethods.Basedonareviewofover29,000crashesatmorethan8,100intersections,lowspeed/lowvolumesignalizedintersectionswerefoundtohavethehighestpercentageofpropertydamageonlycrashes(73%)andthelowestpercentageofinjurycrashes(27%).Inter-sectionswithAll-waySTOPcontrolandlowspeed/lowvolumesignalizedintersectionshadthelowestpercentageoffatalcrashes(0.00%).

• Thedataalsosuggestthat(onaverage)theinstallationofatrafficsignaldoesnotresultinareductionincrashseverity.Theseverityrateatsignalizedintersections,rangingfrom0.5to1.0,isabout25to50%higherthanatintersectionswithThru/STOPcontrol(0.4).

• Thedatasupportsthetheorythatincreasingtheamountofintersectioncontrolsdoesnotresultinahigherlevelofintersectionsafety.

2013 MnDOT Crash Data Toolkit, 2011-2013

Note:OnlyforTrunkHighwayIntersections


Intersection Crash Distributionby Control Type and Rural vs. Urban

Highlights• Thecrashtypedistributionthatcanbeexpectedatanintersectionispri-

marilyafunctionofthetypeofintersectioncontrol.

• Atstop-controlledintersections,inbothruralandurbanareas,themostcommontypesofcrashesarerightangleandrear-endcollisions.

• Atsignalizedintersections,themostcommontypesofcrashesarerear-end,rightangle,andleftturncollisions.

Key Points• Trafficsignalsappeartoreducebutnoteliminaterightanglecrashes.

• Rightturnspresentaverylowriskofacrash(1%to3%ofintersectioncrashes).

• Leftturnspresentaverylowriskofacrash(5%to11%ofintersectioncrashes).

• Crossingconflictspresentaveryhighriskofacrash(20%to50%ofintersectioncrashes).

• Rear-endconflictspresentthehighestriskofacrash(13%to52%ofintersectioncrashes).

• However,whenseverityisconsidered,anewpictureemerges–seepageA-21.



Intersection Crashes – Severity vs. Frequency

Highlights• Whenevaluatingintersection-relatedcrashes,afocusonseverityresultsinavery

differentpriorityofcrashtypesthanifallcrashesareconsidered.

• Themostcommontypeofsevereintersectioncrashisarightanglecollision.

• Rightangleandrear-endcrashesbothaccountforapproximately27%ofallintersection-relatedcrashes.However,therightanglecrashisalmostFOUR timesaslikelytoinvolveafatalityorseriousinjury.

• Theleastseveretypeofintersection-relatedcrashinvolvesright-turningvehicles,whichaccountforapproximately2%offatalitiesandseriousinjuries.

• ThispatternisdifferentwhenlookingspecificallyatSTOPcontrolledvs.Signalcontrolledintersections.Atsignalizedintersections,over45%ofthecrashesarerear-end;however,theyaccountforonly15%oftheseverecrashes.Rightanglecrashesarethemostcommonseverecrash.

• ForSTOPcontrolledintersections,therightanglecrashisthemostcommonandmostseverecrashtype.

STOP Controlled Intersection Crashes

All Intersection Crashes

SIGNAL Controlled Intersection Crashes

Severity/Frequency Combinations


Roadway Segment Crash and Fatality Rates by Jurisdictional Class

• Countyandtownshiproadshadmoderatelyhighcrashratesandthehighestfatalityrates.

• Thisdistributionofcrashesgenerallysupportstheideathatgreaternumbersofcrashesoccurinurbanareasandgreaternumbersoffatalcrashesoccurinruralareas.

• Crashratesandfatalityratesbyroadwayjurisdiction(andforthestateasawhole)areinteresting;however,thereisagreatdealofevidencetosuggestthatcrashratesaremoreafunctionofroadwaydesignthanwhoownstheroad.

Roadway Jurisdiction Classification Miles Crashes Fatalities Crash

Rate* Fatality Rate**

Interstate 916 12,309 25 0.99 0.20

Trunk Highway 10,930 21,221 168 1.04 0.82

CSAH/County Roads 44,958 20,705 151 1.49 1.09

City Streets 22,373 21,975 24 2.42 0.26

Township & Other 63,799 1,497 19 1.21 1.53

State Total 142,976 77,707 387 1.36 0.68

**permillionvehiclemiles(MVM)

**per100millionvehiclemiles(100MVM)

Highlights• Asaclass,interstateshadlowercrashandfatalityratesthanconventionalroad-

ways.Thisfactislikelyduetothreefactors:

• Interstatesonlyserveamobilityfunction

• Interstatestendtohaveaconsistentlyhighstandardofdesign

• Interstateshaveverystrictcontrolofaccess

• Oftheconventionalroadways,trunkhighwayshadthelowestcrashrateandthesecond-lowestfatalityrate.

• Citystreetshadthehighestcrashrateandalowfatalityrate.

2013 Minnesota Roadway & Crash Facts


Roadway Segment Crash Rates Facility Type by Rural vs. Urban

Highlights• Averagecrashratesvarybylocation(ruralvs.urban)andtypeoffacility.

• Freewayshavethelowestcrashratesandarethesafestroadwaysysteminthestate.

• RuralroadwaysasidentifiedintheToolkithavelowercrashratesthansimilarurbanroads.

• Urbanconventionalroadways(notfreewaysorexpressways)–oftenminorarterialswhichservebothamobilityandlandaccessfunction–havethehighestcrashrates.

• Four–laneundividedroadwayshavethehighestcrashrate;thesefacilitiesareusuallyfoundincommercialareaswithhighturningvolumesandwithlittleornomanagementofaccess.Overtheyears,theaveragehasbeenlowered(fromarateof8.0in1990)duetoMnDOT’seffortstoconverttheworstsegmentstoeitherthree-lane,four-lanedivided,orfive-laneroads.Theadditionofleftturnlanestosegmentsofurbanconventionalroadwaystypicallyreducescrashesby25%to40%.

• Thedistributionofcrashratesbyfacilitytypepointstothefollowingrelationshipbetweenaccessdensityandsafety:highwayswithlowlevelsofaccess(freeways)havelowcrashrates,andhighwayswithhigherlevelsofaccess(conventionalroads)havecomparativelyhighercrashrates.

Minnesota County Road Safety Plans, Data 2007-2011 2013 MnDOT Crash Data Toolkit, 2009-2013


Roadway Segment Crash Distribution by Rural vs. Urban

Highlights• Thereisasignificantdifferenceinthetypesofcrashesthatoccuronurban

versusruralroads.

• Urbancrashesarepredominatelytwo-vehicle(about85%),andruralcrashesarepredominatelysingle-vehicle(about55%).

• Themostcommontypesofurbancrashesinclude:

• Rear-end–33%ofallcrashesand7%offatalcrashes

• Rightangle–20%ofallcrashesand20%offatalcrashes

• Themostcommontypesofruralcrashesinclude:

• Run-off-road–44%ofallcrashesand37%offatalcrashes

• Rear-end–12%ofallcrashesand5%offatalcrashes

• Rightangle–9%ofallcrashesand20%offatalcrashes

• Sometypesofcrashesaremoreseverethanothers.Only8%ofallruralcrashesinvolvehead-oncollisions,buttheyaccountfor20%ofthefatalcrashes.

• Deerhitsareunderreportedbecausetheyrarelyresultininjurytovehicleoccupants.Aconservativeestimateisthatasmanyas24%ofruralcrashesinvolvehittingadeer.StateFarmInsuranceestimatesindicatethattherewereapproximately40,000deerhitsinMinnesotain2012.Formoreinfor-mationaboutcollisionsinvolvingadeer,seewww.deercrash.org.

• ThedistributionofcrashesreinforcesthesafetyprioritiesestablishedforbothStateandlocalsystemroadways–rightangleandrear-endcrashesinurbanareasandrun-off-road,rightangleandhead-oninruralareas.


Urban

Rural


Segment Crashes – Severity vs. Frequency

Highlights• Themostcommontypeofsegment-relatedcrashisarear-endcollision(42%).

However,rear-endcollisionsaccountforonlyaround12%ofseriouscrashes.

• Run-off-roadcrashesarethemostcommontypeofseverecrash,accountingfor24%ofthecrashesandover40%ofthefatalandseriousinjurycrashes.

• Head-oncrashesarethesecond-mostseveretypeofcrash,accountingfor8%ofallsegment-relatedcrashesbut20%ofseriouscrashes.

• Segment-relatedcrashesinvolvingrightandleftturningvehiclesarebothinfre-quent(fewerthan5%ofcrashes)andrarelysevere(fewerthan5%ofseriouscrashes).

Segment Crashes – 2-Lane Roadway

All Segment Crashes

Segment Crashes – Multi-Lane Roadway

Severity/Frequency Combinations


Pedestrian/Bicycle Crash Distributionby Intersection Control Type

Highlights• Minnesotaaverages184fatalandseriousinjurycrashesinvolving

pedestriansandbicyclesperyear(approximately14%ofallseverecrashes).

• 66%ofallseriouspedestrian/bicyclecrashesoccurinthesevencountyMinneapolis/St.Paulmetropolitanarea.

• 61%oftheseriouspedestrian/bicyclecrashesintheMetropolitanAreaoccuratanintersectionand81%areonthelocal(cityandcounty)roadsystem.

• 58%oftheseriouspedestrian/bicyclecrashesoccuratintersec-tionscontrolledbytrafficsignals,incontrast30%ofintersectionsaretrafficsignalsontheStatesystemand45%onthecountysystem.

• Basedonthedistributionofcrashesbyintersectioncontroltype,itcanbeconcludedthatseriouscrashesinvolvingpedestrians/bicyclesareoverrepresentedattrafficsignals.

• ThedatasupportstheconclusionthattrafficsignalsaloneareNOTsafetydevicesforpedestriansorbicyclists.(SeepagesC-38-C-41foradiscussionofpedestrianandbicyclesafetystrategies.)

• 61%ofseriouspedestrian/bicyclecrashesoccuronstreetswitha30mphspeedlimitand82%ofthecrashesoccuronstreetswithaspeedlimitof40mphorless.

• Thisdatasupportstheconclusionthatlowerspeedlimitsalonearenotsufficienttoeliminatetheriskoftrafficcrashesforpedestriansandbicyclists.


Crash Location

Intersection Type

Roadway Speed

Roadway Speed at Signalized Crashes

A-27Traffic Safety Fundamentals Handbook – 2015

Pedestrian/Bicycle Crash Distribution by Age

Highlights• Pedestriansbetweentheagesof15and25andthose

olderthan65areinvolvedin38%ofseriousinjurycrashes.

• Bicyclistsbetweentheagesof10and25areinvolvedin42%ofseriousinjurycrashes.

• Beyondtheoverallcrashnumbers,theinvolvementofeachoftheseagegroupswasfoundtobeoverrepresentedwhennormalizedforpopulation.


Age Distribution of Pedestrians and Bicycles Involved in Severe (K+A) Crashes Between 2009 and 2013

B-1

Safety Improvement ProcessSection B

B-2 Minnesota’s Strategic Highway Safety Plan (SHSP)B-3 Minnesota’s Safety Focus AreasB-4 Safety Focus Areas – Greater Minnesota vs. MetroB-5 Behavior Focus Area – SpeedingB-6 – Impaired DrivingB-7 – Inattentive DrivingB-8 – Seat BeltsB-9 Infrastructure Focus Area – IntersectionsB-10 – Lane DepartureB-11 Comprehensive Safety Improvement ProcessB-12 Why Have a Sustained High Crash Location Identification Process?B-13 Alternative Methods for Identifying Potentially Hazardous Locations

B-14 Effect of Random Distribution of CrashesB-15 Calculating Crash RatesB-16 Supplemental Analysis – More Detailed Record ReviewB-17 MnDOT’s Identification of At-Risk Trunk Highway FacilitiesB-18 Systemic Analysis – State HighwaysB-19 Systemic Analysis – County HighwaysB-20 Systemic Analysis – County Highway Crash Data for Greater MinnesotaB-21 – County Highway AssessmentB-22 – County Highway Crash Data for MetroB-23 – County Highway Assessment for MetroB-24 Implementation Guidance for State HighwaysB-25 Implementation Guidance for County HighwaysB-26 Safety Planning at the Local Level


B-2

Minnesota’s Strategic Highway Safety Plan (SHSP)

Highlights• MinnesotaStrategicHighwaySafetyPlan(SHSP)isadata-drivendocumentthat

providesinsightanddirectiononhowtoreducetrafficrelatedcrashes.

• TheSHSPisintendedtoguidesafetyeffortsduringthenext5years.

• Itdocumentsanew,short-termsafetygoal:300orfewerfatalitiesand850orfewerseriousinjuriesby2020.

• Itadoptsalong-termgoalofZEROfatalitiesandidentifieschangingthesafetycultureasafundamentalsafetyfocusarea.

• TheSHSPnotesthattrafficfatalitieshavedecreasedby40%duringthepast10yearsandattributesmuchofthatsuccesstotheformationofMinnesota’sTowardZeroDeathsprogram.

• TheSHSPadoptsseverecrashes–thoseinvolvingfatalitiesandincapacitatinginjuriesasthesafetyperformancemeasureinMinnesota.

• MnDOTSHSPwebsite:www.dot.state.mn.us/trafficeng/safety/shsp/index.html


B-3Traffic Safety Fundamentals Handbook – 2015

Minnesota’s Safety Focus Areas

Highlights• GuidanceprovidedbyFHWAandAASHTOsuggeststhatstateandlocalsafetyprogramswillbe

themosteffectiveiftheirimplementationeffortsarefocusedonmitigatingthefactorsthatcausethegreatestnumberoffatalcrashes.

• AnanalysisofMinnesota’scrashdatadocumentedthefactorsassociatedwithfatalcrashes;theresultssupportdesignatingthefollowingsevenhigh-prioritysafetyfocusareas:

• TrafficSafetyCulture

• Intersections

• LaneDeparture

• Unbelted

• Impaired

• Inattentive

• Speeding

• MnDOTtakestheleadinaddressingtheinfrastructure-basedfocusareasbyadoptingafocusonlanedeparturecrashesinruralareas,establishinggoalsforproactivelydeployinglow-costtreat-mentswidelyacrosssystemsofroadways,andrevisingthemanagementoftheHighwaySafetyImprovementPrograminordertodirectmoreresourcestothoseelementsofthesystemthataremostatrisk–ruralhighwaysandcountyroadways.

• TheMinnesotaDepartmentofPublicSafetytakestheleadinaddressingthedriverbehavior-basedfocusareas,mostlythroughpublicoutreach,educationandhigh-visibilityenforcementprograms.

2014-2019 Minnesota Strategic Highway Safety Plan


Safety Focus Areas – Greater Minnesota vs. Metro

Highlights• Approximately60%oftheseriouscrashesinMinnesotaareinthe79

countiesoutsideofthe8-countyMinneapolis-St.PaulMetropolitanArea.

• Approximately62%ofseriouscrashesoccuronthelocalroadwaysystem,whichalsoresultsinhigherfatalityratesonthelocalsystem.

2014-2019 Minnesota Strategic Highway Safety Plan, Data 2008-2012

Driver Behavior-Based Focus Areas Infrastructure-Based Focus AreasTotal Severe

Crashes Unbelted Impaired Inattentive Speeding Lane Departure Intersection

Statewide7,036 2,463 1,850 1,319 1,309 3,199 2,945

Greater Minnesota Districts (2008-2012 Severe Crashes)StateTrunkHighway 1,813 666 414 430 326 919 686

CountyRoads 1,699 743 580 309 342 1,017 545

City 435 141 99 70 87 146 224

Township 278 150 116 24 73 175 62

Other 17 3 9 1 4 9 2

Greater Minnesota Total 4,242 1,703 1,218 834 832 2,266 1,519

Metro District (2008-2012 Severe Crashes)StateTrunkHighway 831 242 216 179 172 295 360

CountyRoads 1,148 285 223 200 151 386 668

City 786 222 182 106 148 237 391

Township 22 11 10 0 5 11 6

Other 7 0 1 0 1 4 1

Metro District Total 2,794 760 632 485 477 933 1,426

• Inruralareas,theprimaryfactorsassociatedwithseriouscrashesarenotusingsafetybelts,impaireddriving,androaddeparture.

• Inurbanareas,theprimaryfactorsassociatedwithseriouscrashesareintersections,notusingsafetybelts,impaireddriving,andinattentive/distracteddriving.


Behavioral Focus Area – Speeding

Highlights• OnMinnesotaroadways,therewere1,309severespeeding-relatedcrashes

between2008and2012.Thisisanaverageof262severecrashesperyear,accountingfor19%ofallseverecrashesduringthe5-yearperiod.

• Severecrashesinvolvingspeedarenotablyrepresentedwithinbothstateandlocalroadwaysystems,aswellasinbothrural(55%)andurban(41%)areas,asdefinedbyinvestigatingofficers.

• 70%ofseverespeeding-relatedcrashesinruralareasoccuronruralhigh-speedtwo-laneroads.

• 58%ofseverespeeding-relatedcrashesonruralcountyroadsoccuralongcurves,comparedto39%onallroadwaysstatewide.

• Severecrashesinvolvingspeedoccuramongdifferingcrashtypes:

• 62%arelanedeparturecrashtypes.

• 70%ofseverespeed-relatedcrashesoccurondrypavement.

• Driversaged35andyoungeraccountfor63%ofspeeding-relatedseverecrashes;77%ofdriversinseverespeeding-relatedcrashesaremale.

• Thenumberofspeed-relatedcrashesfellsteadilybetween2004and2010andthenflattenedout.

• Duringthe2004to2010timeframe,theStatesponsoredtwoenhancedenforce-mentcampaigns(HEAT–HighEnforcementofAggressiveTraffic)focusedonticketingspeedingdriversandreducingthenumberofseverespeeding-relatedcrashes.

• Nearlyequalnumbersofspeeding-relatedcrashesoccuronthestateandcountyroadwaysystemsandthesesystemsexperiencedthegreatestreductionovertime.



Highlights• OnMinnesotaroadways,therewere1,850severecrashesinvolvingimpaired

driversandroadwayusersbetween2008and2012.Thisisanaverageof370severecrashesperyearandaccountedfor26%ofallseverecrashesduringthe5-yearperiod.

• Severecrashesinvolvingimpairedroadwayusersoccuracrossallroadwayjurisdictionsandinbothruralandurbanareas.However,mostseverecrashesoccurredonruralroads(58%),asdefinedbyinvestigatingofficers.

• 74%ofseverecrashesinvolvingimpairedusersinruralareasoccuronrural,high-speed,two-laneroads.

• Lanedepartureaccountsfor64%ofallseverecrashesinvolvingimpairedroadwayusers.

• Severeimpaired-usercrashesarenearlytwiceaslikelytooccuratnightastheaverageforallseverecrashes;48%ofsevereimpaired-usercrashesoccurbetween9:00PMand3:00AM.

• Overall,malesandyoungadultsareoverrepresentedinimpaired-relatedcrashesandaccountforadisproportionateshareoffatalities.In2013,malesaccountedfor67%ofimpaired-drivingarrests.However,from2003to2013,femaleDWIoffensesincreased5%.

• Thenumberofalcohol-relatedcrashesfellsteadilybetween2004and2010,buthassinceincreasedslightly.

• Duringthe2004to2010timeframe,theStateadoptedtwonewalcohol-relatedstrategies:loweringtheBloodAlcoholConcentrationthresholdfrom0.1to0.08andinitiatingtheuseofignitioninterlockdevices.

• Disaggregatedbysystem,countyroadwayshavehadmorealcohol-relatedcrashesthanstatehighwaysorcitystreets.

Behavioral Focus Area – Impaired Driving



Highlights• Whileanythingthattakesyoureyesofftheroad,handsoffthewheel,ormind

offdrivingisahazard,texting/readingemail/accessingtheinternetisparticularlydangerous,bycombiningallthreetypesofdistraction–visual,manual,andcognitive.

• OnMinnesotaroadways,therewere1,319severecrashesinvolvinginattentivedriversbetween2008and2012.Thisisanaverageof264severecrashesperyearandaccountedfor19%ofallseverecrashesduringthe5-yearperiod.

• Themajorityofsevereinattentivedrivingcrashesdonotoccurunderadversedrivingconditions:

• 92%ofthesecrashesoccurduringcalmweatherconditions(clearorcloudy).

• 70%ofthesecrashesoccurduringdaylight.

• 84%ofthesecrashesoccurondrypavement.

• Severecrashesinvolvinginattentivedriversoccuramongdifferingcrashtypes,with46%intersection-relatedand39%lanedeparture-related.

• Intersectioncrashtypesoccurpredominantlyonstraightsegments(92%),butthepresenceofcurvesnearlydoublestheoccurrenceoflanedeparturecrashtypes(36%).

• Severecrashesinvolvinginattentivedriversarenotablyrepresentedinbothrural(54%)andurban(44%)areas,asdefinedbyinvestigatingofficers.

• 71%ofsevereinattentivedrivingcrashesinruralareasoccuronruraltwo-laneroadswithahighspeedlimit.

Behavioral Focus Area – Inattentive Driving



Highlights• OnMinnesotaroadways,therewere2,463severecrashesinvolvinganunbelted

orimproperlybeltedoccupantbetween2008and2012.Thisisanaverageof493severecrashesperyearandaccountedfor35%ofallseverecrashesduringthe5-yearperiod.

• Severecrashesinvolvingunbeltedorimproperlybeltedoccupantsprimarilyoccurredinruralareas(61%),asdesignatedbyinvestigatingofficers;themajorityofthesecrashesoccurredonlocalroadways(63%).

• 74%ofseverecrashesinvolvingunbeltedoccupantsinruralareasoccuronrural,high-speedtwo-laneroads.

• Severecrashesinvolvingunbelteddriversoccuramongdifferingcrashtypes,with42%asrun-off-roadcrashes,ascomparedto30%forallseverecrashes.

• Duringthe2004to2010timeframe,thestateadoptedaprimaryseatbeltlaw–thisallowslawenforcementtostopandticketdriversiftheyarenotwearingasafetybelt.Minnesota’sseatbeltlawisaprimaryoffense,meaningdriversandpassengersinallseatingpositionsmustbebuckleduporinthecorrectchildrestraintorlawenforcementwillstopandticketunbelteddriversorpassengers–includingthoseinthebackseats.

• Minnesotaoccupantrestraintusagerateis95%(June,2013)–thehighestinMinnesotahistory.Nationally,seatbeltuseismuchlower(86%in2012).

• A2014studysponsoredbytheMinnesotaDepartmentofPublicSafetyandledbytheUniversityofMinnesotaHumphreySchoolofPublicAffairsindicatethatfromJune2009(whenMinnesota’sprimarylawwasimplemented)throughJune2013,therewereatleast132fewerdeaths,434fewersevereinjuries,and1,270fewermoderateinjuriesthanexpectedwithoutaprimaryseatbeltlaw.Forfurtherinformation,seeEvaluation Update on the Effectiveness of the Minnesota Primary Seatbelt Lawatwww.cts.umn.edu/Research/ProjectDetail.html?id=2014053.

Behavioral Focus Area – Seat Belts



Highlights• Intersection-relatedcrashesaccountfornearly42%ofallseverecrashesin

Minnesota.

• Thenumberofintersection-relatedcrashesfellsteadilybetween2004and2011andthenincreasedslightly.

• ThemostfrequenttypeofseverecrashatbothSTOP(55%)andsignalcontrolled(38%)intersectionsinvolvesarightanglecollision.

• Inresponsetotheoverrepresentationofrightanglecollisionsatintersec-tions,agencieshaveimplementedvariousintersectionsafetystrategiessuchaslightingatruralcountyroadintersections,innovativedesignsthatlimitaccessatexpresswayintersections,andnewtechnologytohelplawenforcementaddressredlightviolationsattrafficsignals.

• Disaggregatedbysystem,Countyroadwayshavethegreatestnumberofintersection-relatedcrashesfollowedbyStatehighwaysandthenCitystreets.

Infrastructure Focus Area –Intersections



Highlights• Lanedeparture-relatedcrashesaccountforapproximately45%ofallsevere

crashesinMinnesota.

• Thenumberoflanedeparture-relatedcrashesfellsteadilybetween2004and2011andthenincreasedslightly.

• Roadwayfeaturesthatcontributetolanedeparturecrashesincludethelackofuseableshoulders,steepslopes,andfixedobjectsintheditches.Oneadditionalfeature,thepresenceofcurves,especiallythosewithradiiunder1,200feet,isassociatedwithsinglevehicleroaddeparturecrashes.Onthecountysystemmorethanone-halfofthesecrashesoccuralongcurvesandapproximatelyone-thirdofthestatesystem.

• Inresponsetothesecrashes,theStateandCountyagenciesimplementedvariouslanedeparturesafetystrategiessuchasedgelineandcenterlinerumblestripsandtheadditionofchevronsalongruralhorizontalcurves.

• Disaggregatedbysystem,Countyroadwayshavethegreatestnumberoflanedeparture-relatedcrashes,followedbyStatehighways.

Infrastructure Focus Area –Lane Departure



Comprehensive Safety Improvement Process

Highlights • Forthepast30years,mostsafetyprogramshavebeenfocusedonidentifying

locationswithahighfrequencyorrateofcrashes–SustainedHighCrashLocations(SHCLs)–andthenreactivelyimplementingsafetyimprovementstrategies.

• AlocationisgenerallyconsideredtobeanSHCLifitssevere(fatalandincapacitatinginjury)crashrateexceedsitsseverecriticalcrashrate.

• TheresultofmakingSHCLsthehighestpriorityinthesafetyprogramwastofocussafetyinvestmentsprimarilyonurbanandsuburbansignalizedintersections–thelocationswiththehighestnumberofcrashes.However,intersectionsidentifiedasSHCLsdonotaccountforallfatalcrashes.

• AreviewofMnDOT’sTrunkHighwaySystemfoundatotalofthreeintersectionsthataveragedoneseverecrashperyear.

• Anew,moresystemicanalysisofMinnesota’scrashdata,combinedwiththeadoptionofagoaltoreducefatalcrashes,hasledtoamorecomprehensiveapproachtosafetyprogramming–afocusonSHCLsinurbanareaswherethereareintersectionswithhighfrequenciesofcrashesandasystems-basedapproachforruralareaswherethetotalnumberofseverecrashesishighbuttheactualnumberofcrashesatanygivenlocationisverylow.

Analytical Techniques

Implementation Strategies

Reactive

Site Analysis at Sustained High Crash Locations

Systemwide Analysis Proactive

Comprehensive Safety Improvement Process


Why Have a Sustained High Crash Location Identification Process?

Highlights • Conductingperiodicreviewsofyoursystemtoidentifylocationswithasustainedhigh

crashfrequencysupportsprojectdevelopmentactivitiesandareanintegralpartofabestpracticesapproachtoriskmanagement.Monitoringthesafetyofyoursystemisgoodpracticeandistheindustry“norm”againstwhichyouwillbeevaluated.

Project Development

• Crashesareonemeasurableindicatorofhowwellasystemofroadwaysandtrafficcon-troldevicesisfunctioning.

• UnderstandingsafetycharacteristicscanassistintheprioritizationanddevelopmentofroadwayimprovementprojectsbyhelpingdocumentPurposeandNeed.

Risk Management

• Activelyidentifyingpotentiallyhazardouslocationsisbetterthanbeinginthemodeofreactingtoclaimsofpotentiallyhazardouslocationsbythepublic(orplaintiff’sattor-neys).

• Knowledge(actualorconstructive)ofhazardousconditionsisoneoftheprerequisitesforprovinggovernmentagencynegligenceintortcasesresultingfrommotorvehiclecrashes.

• Allcrashanalysisperformedaspartofasafetyimprovementprogramisnot subject to discoveryintortlawsuits.

Data Systems

• Inordertobeabletodevelopcountermeasurestomitigatetheeffectsofcrashes,agen-ciesneedamonitoringsystemtoidentifycrashlocationsandthekeycharacteristicsandcontributingfactorsassociatedwiththecrashes.TheMnDOT“Toolkit”providesallofthenecessarycrash,roadwayandtrafficcontrolcharacteristicsforsegmentsandinter-sectionsontheTrunkHighwaysystem.MnCMATpluslocalagencyinventorieswouldprovidethedatanecessarytosupportsiteanalysesatlocationsidentifiedashavingsustainedhighcrashfrequencyorrateofcrashesalongcountyroadsandcitystreets.

“Rural”referstoanon–municipalareaandcitieswithapopulationlessthan5,000.


Alternative Methods for Identifying Potentially Hazardous Locations

1 Number of Crashes annually is greater than X crashes per year.

2 Crash Rate is greater than Y crashes per million vehicles annually.

3 Critical Rate is a statistically adjusted Crash Rate to account for random nature of crashes.

Highlights• Therearethreeprimarymethodsforidentifyingpotentiallyhazardouslocations.

• ThefirstmethodwouldinvolvesettinganarbitrarythresholdvalueofXcrashesperyearatanyparticularlocation.Thismethodisthesimplestapproachwiththefewestdatarequirements.However,theselectionofthethresholdvalueissubjectiveandthismethodologydoesnotaccountforvariationsintrafficvolumeorroadwaydesign/trafficcontrolcharacteristics.Thismethodisbetterthannothingandwouldbemostapplicableinsystemsconsistingofsimilartypesofroadswithonlysmallvariationsintrafficvolumes.

• ThesecondmethodconsistsofcomputingcrashratesandthencomparingthemtoanarbitrarilyselectedthresholdvalueofYcrashesperunitofexposure(acrashrate).

Advantage:• Allowscomparisonoffacilitieswith

differenttrafficvolumes.

Disadvantages:• Subjectiveselectionofthethresholdvalue.

• Requiresmoredata(trafficvolumes).Doesnotaccountforknownvariationincrashratesamongdifferenttypesofroaddesigns.

• Doesnotaccountfortherandomnatureofcrashes.

Conclusion: Limitedapplicability,betterthanusingcrashfrequencyonly.

• ThethirdmethodinvolvesusingastatisticalqualitycontroltechniquecalledCriticalCrashRate.

Advantage:• Onlyidentifiesthoselocations

ashazardousiftheyhaveacrashratestatisticallysignificantlyhigherthanatsimilarfacilities.

Disadvantage: • Mostdata-intensivemethodology(volumesand

categoricalaverages).

Conclusion: Ofthethreemethods,criticalcrashrateisthemostaccurateandstatisticallyreliablemethodforidentifyinghazardouslocations.


Effect of Random Distribution of Crashes

Highlights

The Concept of Critical Crash Rate

• Thetechniquethatusesthecriticalcrashrateisconsideredtobeahighlyeffectivetech-niqueforidentifyinghazardouslocations.

• Thecriticalcrashrateaccountsforthekeyvariablesthataffectsafety,including:

• Thedesignofthefacility

• Thetypeofintersectioncontrol

• Theamountofexposure

• Therandomnatureofcrashes

• Theconceptsuggeststhatanysampleorcategoryofintersectionsorroadwaysegmentscanbedividedintothreebasicparts:

• Locationswithacrashratebelowthecategoricalaverage:TheselocationsareconsideredtobeSAFEbecauseofthelowfrequencyofcrashesandcanbeeliminatedfromfurtherreview.

• Locationswithacrashrateabovethecategoricalaverage,butbelowthecriticalrate:TheselocationsareconsideredtobeSAFEbecausethereisaveryhighprobability(90-95%)thatthehigherthanaveragecrashrateisduetotherandomnatureofcrashes.

• Locationswithacrashrateabovethecriticalrate:TheselocationsareconsideredtobeUNSAFEandinneedoffurtherreviewbecausethereisahighprobability(90-95%)thatconditionsatthesitearecontributingtothehighercrashrate.

• Theotheradvantageofusingthecriticalcrashrateisthatithelpsscreenout90%ofthelocationsthatdonothaveaproblemandfocusesanagency’sattentionandresourcesonthelimitednumberoflocationsthatdohaveadocumentedproblem(asopposedtoaperceivedproblem).

• Therelationshipbetweenthecriticalcrashrateandthelevelofvehicularexposureshouldbenoted.Asthevolumeoftrafficattheintersectionorsegmentbeingstudiedincreases,thedifferencebetweenthesystemaverageandthecriticalratediminishes.


Calculating Crash Rates

Highlights• Thenumberofcrashesatanylocationisusuallyafunctionofexposure.As

thenumberofvehiclesenteringanintersectionorthevehiclemilesoftravelalongaroadwaysegmentincrease,thenumberofcrashestypicallyincrease.

• Theuseofcrashrates(crashfrequencypersomemeasureofexposure)accountsforthisvariabilityandallowsforcomparinglocationswithsimilardesignsbutdifferentvolumes.

• Intersectioncrashratesareexpressedasthenumberofcrashespermillionenteringvehicles.

• Segmentcrashratesareexpressedasthenumberofcrashespermillionvehiclemiles(oftravel).

• Thecriticalcrashrateiscalculatedbyadjustingthesystemwidecategoricalaveragebasedontheamountofexposureanddesiredstatisticallevelofconfidence.

LevelofConfidence 0.995 0.950 0.900K 2.576 1.645 1.282

MEV MillionEnteringVehiclesMVM MillionVehicleMilesADT AverageDailyTrafficoneachlegenteringanintersection

orthedailytwo-wayvolumeonasegmentofroadway

• Thedifferencebetweenthesystemwidecategoricalaverageandthecriticalrateincreasesasthevolumedecreases.

• Whencomputingthecriticalcrashrate,thetermm(vehicleexposure)isthedenominatorintheequationsusedinthecalculationofeithertheintersectionorseg-mentcrashrate.

• Thesameformulascanbeusedtocalculatecriticalfatalityorinjuryrates,ortherateatwhichaparticulartypeofcrashisoccurring.

• Agoodruleofthumbistouse3to5yearsofcrashdatawhenavailable.Moredataarealmostalwaysuseful,butincreasestheconcernaboutchangedconditions.Usingonly1or2yearsofdatapresentsconcernsaboutsamplesizeandstatisticalreliability.

• Safetyanalystsshouldbeawareoftheeffectsamplesizehasontheoveralllevelofcredibilityassignedtotheresultsoftheirstudies.Asthenumberofcrashesinthestudyincreases,thepercentchangeneededtobestatisticallyreliablediminishes.

RateperMVM =(numberofcrashes)x(1million)

(segmentlength)x(numberofyears)x(ADT)x(365)

Segment Rate:

Intersection Rate:

RateperMEV =(numberofcrashes)x(1million)

(numberofyears)x(ADT)x(365)

Severity Rate:

RateperMVM =((5xnumberofKs)+(4xno.As)+(3xno.Bs)+(2xno.Cs)+no.PDOs)x(1million)

(numberofyears)x(ADT)x(365)

Rc=Ra+Kx(Ra/m)½+0.5/m Rc= CriticalCrashRate –forintersections:crashesperMEV –forsegments:crashesperMVMRa=SystemWideAverageCrashRatebyIntersectionorHighwayTypem=VehicleExposureDuringStudyPeriod –forintersections:yearsxADTx(365/1million) –forsegments:lengthxyearsxADTx(365/1million) k=ConstantbasedonLevelofConfidence

Critical Rate:

NumberofCrashes(SampleSize) 10 30 65 125 200

PercentChange(95%Level) 50% 30% 20% 15% 12%

Safetyanalystsshouldbeawareoftheeffectsamplesizehasontheoveralllevelofcredibilityassignedtotheresultsoftheirstudies.Asthenumberofcrashesinthestudyincreases,theper-centchangeneededtobestatisticallyreliablediminishes.


Supplemental Analysis – More Detailed Record Review

Highlights • Afteridentifyinghazardouslocations,thenextstepisto

conductsupplementalanalysesinordertobetterunderstandthenatureoftheproblemandtohelpdevelopappropriatemitigativestrategies.

• Amoredetailedunderstandingofthecontributingfactorsisnecessarytodevelopcountermeasuresbecausethereiscurrentlynoexpertsysteminplacethatallowsmappingfromahighcrashratetothebasesafetysolution.Trafficengineersneedtoknowmoreabouttheparticularproblemsatspecificlocationsbecauseour“Toolkit”isfarlessdevelopedthanotherareasofroadwayengineering.

• ThesupplementalanalysisofcrashdatainvolvescomparingACTUALcrashcharacteristicstoEXPECTEDcharacteris-ticsandthenevaluatingfordifferences.Thesedifferencesdocumentcrashcausationfactorsthathelpidentifyeffectivecountermeasures.

• Itisimportanttorememberthatroadsthataresimilarindesign,withsimilarvolumes,willoperateinasimilarmannerandwillprobablyhavesimilarcrashcharacteristics.

• MnDOT’s“Toolkit”andtheinformationprovidedinSectionAofthishandbookprovideinsightaboutexpectedcondi-tionsalongMinnesota’sroadways.

• TheHighwaySafetyManual(seepageC-8)cancontributetoadetailedanalysisbydocumentingSafetyPerformanceFunctions(SPFs)thatcomputetheexpectedcrashfrequencyforavarietyofroadwaycross-sectionsandintersectiontypes.


Highlights • MnDOTusesanumberoftechniquestoidentifypotentiallyhazardouslocations,

includingcriticalcrashrate,crashfrequency,crashseverity,andcrashcost.

• MnDOTpublishesanannualTop200listofhigh-crash-rateintersectionsalongthestate’s12,000-miletrunkhighwaysystemonanannualbasis.

• Thelistranksintersectionsbycrashcost,frequency,severity,andrate.

• Intersectionsonthelistgenerallyhavethefollowingcharacteristics:

• Crashfrequenciesbetween1and63peryear.

• Crashratesbetween0.2and5.7crashespermillionenteringvehicles.

• Crashcostsbetween$0.26millionand$1.2millionperyear.

• Listedintersectionsareoverwhelminglysignalized(70%)andinurbanareas(69%).

• Ingeneral,thislistdoesNOTadequatelyidentifyintersectionswithsafetydeficienciesinruralareas.

• Thisapproachalsodoesnotnecessarilyidentifylocationswithfatalcrashes(fewerthan10%offatalcrashesinMinnesotaoccurredatintersectionsintheTop200list).

• Thekeypointisthatahighcrashrateanalysisshouldcontinuetobeanecessarypartofacomprehensivesafetyprogram,butasystemicevaluationshouldalsobeperformed.

• AreviewofMnDOT’sTrunkHighwaysystemfoundatotalofthreeintersectionsthataveragedoneseverecrashperyearandtheanalysisconductedonthecountysystem(aspartoftheCountyRoadSafetyPlans)lookedatover13,000ruralintersectionandnointersectionaveragedoneseverecrashperyear.

MnDOT’s Identification of At-Risk Trunk Highway Facilities

Kittson Roseau

Marshall

Pennington

Red Lake

Clay Becker Wilkin

Otter Tail

Traverse Grant Douglas

Wadena

Todd

Crow Wing

Morrison

Mille Lacs

Kanabec Pine

Chisago Isanti Sherburne

Wright

Benton

Meeker

Stearns Pope Stevens Big Stone

Swift Chippewa

Yellow Medicine

Lincoln Lyon Redwood

Sibley Scott

Goodhue

Dodge

Mower Fillmore

Olmstead

Wabasha

Winona

Houston

Pipestone Murray Cottonwood

Brown Le Sueur Rice

Martin Faribault Freeborn

Watonwan Waseca

Steele Blue Earth

Lac Qui Parle Kandiyohi McLeod Carver

Mahnomen

Beltrami

Lake of the Woods

Koochiching

St. Louis

Dakota

Lake

Cook

Itasca

Aitkin

Cass Hubbard

Clear-water

Norman

Dakota

Ramsey

Rock Nobles Jackson

Hennepin

Polk

Wash- ington

Anoka

6

2

8

7

1

34

METRO


Crash Summary by Facility Types – Greater Minnesota Districts

Facility Type Miles

CrashesCrash Rate

Severity Rate Fatal Rate

Crash DensityFatal

Serious Injury

Rura

l

Freeway 742.8 62 141 0.54 0.61 0.27 3.394-LaneExpressway 735.8 99 169 0.65 1.12 0.66 2.684-LaneUndivided 27.5 2 3 0.63 0.80 0.53 1.734-LaneDividedConventional(Non-Expressway) 103.6 13 27 0.82 1.40 0.67 3.06

2-La

ne

ADT<1,500 3,953.2 99 171 0.64 2.59 1.50 0.211,500<ADT<5,000 3,744.3 184 299 0.54 1.56 0.96 0.565,000<ADT<8,000 556.4 54 96 0.59 1.51 0.85 1.35ADT>8,000 126.4 17 30 0.56 1.18 0.67 2.23

Sub Total 9,990 530 936

Urb

an

Freeway 20.6 4 16 1.33 1.00 0.25 20.734-LaneExpressway 44.1 7 30 2.16 2.35 0.55 12.524-LaneUndivided 42.7 4 18 3.05 2.06 0.46 12.464-LaneDividedConventional(Non-Expressway) 55.3 8 31 2.43 1.80 0.47 15.123-Lane 26.3 6 4 2.02 0.87 1.31 7.055-Lane 16.9 0 8 2.39 1.84 0.00 12.34

2-La

ne

ADT<1,500 77.2 5 10 1.91 7.74 3.87 0.641,500<ADT<5,000 266.9 12 25 1.35 1.78 0.85 1.435,000<ADT<8,000 96.5 4 33 1.80 2.95 0.36 4.17ADT>8,000 51.7 2 24 2.29 2.41 0.20 8.80

Sub Total 698 52 199

Crash Summary by Facility Types – Metro District

Facility Type Miles

CrashesCrash Rate

Severity Rate Fatal Rate

Crash DensityFatal

Serious Injury

Rura

l

Freeway 122 22 24 0.6 0.9 0.5 11.14-LaneExpressway 111 17 65 1.0 1.5 0.7 10.34-LaneUndivided 0 0 0 2.5 3.1 0.0 14.84-LaneDividedConventional(Nonexpressway) 1 0 0 1.3 2.0 0.0 9.2

2-La

ne

ADT<1,500 13 0 2 0.0 0.0 0.0 0.51,500<ADT<5,000 89 5 8 1.0 1.5 2.0 1.35,000<ADT<8,000 98 8 18 1.2 2.0 1.8 2.7ADT>8,000 137 17 33 1.3 2.0 1.2 6.9


Urb

an

Freeway 267 43 128 1.2 1.6 0.2 41.74-LaneExpressway 124 17 81 1.9 2.7 0.5 23.94-LaneUndivided 20 2 25 5.8 7.8 0.7 41.34-LaneDividedConventional(Nonexpressway) 21 3 19 5.0 6.8 0.9 38.63-Lane 9 0 2 3.1 4.3 0.0 16.85-Lane 2 0 3 5.6 8.8 0.0 52.4

2-La

ne

ADT<1,500 1 0 0 4.0 6.3 0.0 2.11,500<ADT<5,000 9 0 0 2.8 3.9 0.0 3.75,000<ADT<8,000 26 2 2 2.3 3.3 1.6 5.5ADT>8,000 54 6 20 3.0 4.2 1.1 15.6


Systemic Analysis – State HighwaysHighlights • Historically,theabsenceofsustainedhighcrashlocationsin

asystemofroadswasinterpretedtomeanthattherewerenosafetydeficienciesandthattherewerenoopportunitiestoeffectivelymakeinvestmentstoreducecrashes.

• However,anewinterpretationofthecrashdatabytheFHWAandanincreasingnumberofstatedepartmentsoftransportationsuggeststhatneitherassumptioniscorrect.

• AreviewofMinnesota’scrashdata,conductedaspartoftheSHSP,providesseveralinsightsinsupportofasystemicapproachforaddressingsafetydeficiencies.

• Onthestate’shighwaysystem,thefacilitytypesthatpresentthegreatestopportunitytoreducefatalcrashes(basedonthetotalnumberoffatalcrashes)areruraltwo-laneroads(50%)andfreeways(22%).However,untilrecentlytherehavebeenfewprojectsonthesefacilitiesbecausetheprocessoffilteringthedatafailedtoidentifyanysustainedhighcrashlocations.

• Furtheranalysisofthesepriorityfacilitiesshowsthatneithertheoverallcrashratenorthefatalityrateisatallunusual,butthepooloffatalcrashessusceptibletocorrectionisstilllargeandrepresentsthegreatestopportunityforreduction:addressingroaddeparturecrashesonruraltwo–laneroadsandcross-mediancrashesonfreeways.

• Thefinalpointinsupportofasystemicapproachtoaddresssafetyinruralareasistheverylowdensityofcrashesalongruraltwo-lanehighways–61%offatalcrashesoccuronthe87%ofthesystemthataverageslessthanonecrashpermileperyear.

2013 MnDOT Crash Data Toolkit, 2009-2013

Note:Crashrateiscrashespermillionvehiclemiles;fatalityrateisfatalcrashesper100millionvehiclemiles.


Systemic Analysis – County Highways

Highlights • Historically,theprimarycandidatesforsafetyinvestmentwerelocationsidenti-

fiedashavingahighfrequencyofcrashescomparedtoothersimilarintersectionsorroadwaysegments(frequentlyreferredtoassustainedhighcrashlocationsorSHCLs).

• Overtime,itwasrecognizedthatthisapproachhadtwodistrictdisadvantages:

• First,thisapproachmadehighwayagenciesentirelyreactive(agencystaffhadtotrytorespondtothephonecallthatasked–“Howmanypeoplehavetodiebeforeyoudosomething?”)

• Second,in2005FHWArequiredstatestobasetheirsafetyprogramsonseverecrashes(fatal+seriousinjury)insteadofallseverities.SubsequentanalysisfoundthatthereareonlyafewlocationsinMinnesotawheremultipleseverecrashesoccurandvirtuallynonealonglocalsystems.

• Inresponse,MnDOTaddeda“systemic”componenttoitsHighwayImprovementProgramtocomplementthehistoricreactivecomponent.

• Thesystemicapproachusescrashsurrogates–roadwayandtrafficcharacteristicsthatappeartobeoverrepresentedatthelocationsaroundMinnesotawhereseriouscrashesoccur–toidentifyat-risklocationsthatarecandidatesforsafetyinvestment.

• Thesystemicapproachwasusedtopreparesafetyplansforall87countiesinMinnesota.Theanalysesofeachcounty’ssystemofroadsidentifiedthetypesofcrashesthatrepresentthegreatestopportunityforreductions,theshortlistofhighlyeffectivestrategiesandaprioritizedlistofcandidatelocationsforsafetyinvestmentbasedonthepretenseofroadwayandtrafficcharacteristicsthatwereassociatedwithlocationswithseverecrashes.Theoutcomeoftheeffortwastheidentificationofover17,000projectswithanestimatedimplementationcostofapproximately$246M.Itshouldbenotedthatnotasinglelocationidentifiedasbeingat-riskalongthecountysystemaveragedoneseverecrashperyearandwouldnothavebeenidentifiedasahigh-crashlocation.

Intersections with multiple severe crashes

in 5-year period.

Intersections considered high priority based on risk

assessment.


Highlights

Greater Minnesota Crash Data Overview

• The“systemic”approachhasprovedtobepar-ticularlyeffectiveatidentifyingat-risklocationsforsafetyinvestmentalongMinnesota’scountyhighwaysystem.

• IngreaterMinnesota,thenumberofseverecrashesonthecountyroadwaysystemisvirtuallyidenticaltothenumberonthestatesystem(approximately500severecrashes/year).However,thetwomostcommontypes–roaddepartureandrightanglecrashes–arescatteredacrossalmost27,000milesofpavedroadsand13,000intersections.Thisresultsinaveragedensitiesof0.007permileand0.006perintersection.Inaddition,morethan90%ofthesefacilitieshadNOseverecrashes(over5years)andNONEaveragedoneseverecrashperyear.

• Thetraditionalreactive-basedanalysiswouldhaveconcludedthatthereareNOcandidatesforsafetyinvestment.Therisk-basedsystemicanalysiscametoadifferentconclusionandidentifiedapproximately$232Mofroadedge,curvedelineation,andinter-sectionsafetyimprovementsbasedontheprobabilityofacrashoccurringatthelocationwithmultipleriskfactorspresent.


ATP’s 1, 2, 3, 4, 6, 7, and 8 – NO Metro

Severeisfatalandseriousinjurycrashes(K+A)

Systemic Analysis – County HighwayCrash Data for Greater Minnesota


Highlights

Risk Rating Criteria for Rural Paved Roads

• ThesystemicriskassessmentofMinnesota’sruralcountyhighwaysusedavarietyofroadwayandtrafficcharacteristicsidentifiedfromareviewofpublishedsafetyresearchandinformationobtainedaboutthespecificlocationsinMinnesotawheresevereroaddepartureandrightanglecrashesoccurred.

• Thesystemofpaved,secondaryroadswasanalyzedineverycounty.Thisanalysisusedaerialphotography,videologs,andMnCMATtoidentifythecharacteristicsofeachsegment,horizontalcurve,andintersection.

• Theresultsoftheanalysisincludedprioritizedlistings(basedonthenumberofriskfactorspresent)ofsegments,curves,andintersectionsforeverycounty.Thepriorityliststypicallyidentifiedapproximately25%to30%ofeachcounty’sfacilitiesofbeingat-riskandthereforecandidatesforsafetyinvestment.

Roadway and Traffic Characteristics

Segments – Density of Road Departure– Traffic Volume– Critical Curve Radius Density– Access Density– Edge Risk Assessment

Curves – ADT Range– Radius Range – Severe Crash on Curve– Intersection on Curve

Intersections – Skewed Approaches– On/Near Curve– Volume– Proximity to Railroad Crossing– Proximity to Last STOP Sign– Intersection-Related Crashes– Commercial Development in

Quadrant

Systemic Analysis – County Highway Assessment


Highlights

Metro County Crash Data Overview

• ThesystemicapproachwasalsoappliedtotheurbancountiesintheMinneapolis–St.PaulMetropolitanArea.Inthesecounties,thenumberofcrashesexceedsthenumberontheStatesystembyalmost45%.

• Themostcommontypesofseverecrashesinclude,forsegments:

• Rear-end

• Sideswipe

• Head-on

• Forintersectionsthemostcommenttypeofseverecrashesare:

• Rightangle

• Pedestrian/bicyclist

• However,thecrasheswerescatteredoveralmost1,600milesofroadwayand2,900intersections.Thisresultsinaveragedensi-tiesof0.05severecrashes/mile,and0.01crashes/intersections.Inaddition,approximately90%oftheurbanfatalitieshadNOseverecrashesandNONEaveragedoneseverecrashperyear.

• Aswasthecaseinruralareas,thetraditionalreactiveanalysiswouldhaveconcludedthatthereareNOcandidatesforsafetyinvestmentbasedonlyonthepresenceofcrashes.Therisk-basedsystemicanalysisidentifiedapproximately$14Mofsegmentandintersectionsafetyimprovementsthatcouldbedeployedproactivelythatwouldpreventtheoccurrenceoftheprioritycrashtypes.

Severeisfatalandseriousinjurycrashes(K+A)


Systemic Analysis – County Highway Crash Data for Metro


Highlights

Risk Assessment Findings – Urban Intersection

• Thesystemicriskassessmentoftheurbancountyhighwaysidentifiedtheroadwayandtrafficcharacteristicsthatwerecommontothelocationswheretheprioritycrashtypesoccurred:rightangleandped/bikecrashes.Alloftheurbancountyhighwayswerethenevaluatedusingaerialphotography,videologs,andMnCMATforpresenceofthesefeatures.

• Theresultoftheanalysisincludedprioritizedlistingsofsegmentsandintersectionsforeverycounty.Aswasthecasewiththeruralcounties,theprioritylistsfortheurbancountiestypicallyidentifiedapproximately25%to30%ofeachcounty’sfacilitiesofbeingatriskandcandidatesforsafetyinvestment.

Roadway and Traffic Characteristics

Urban Intersections (Right Angle Crashes)

– Density of Road Departure– Traffic Volume– Critical Curve Radius Density– Access Density– Edge Risk Assessment

Urban Intersections (Pedestrian/ Bicycle Crashes)

– ADT Range– Radius Range – Severe Crash on Curve– Intersection on Curve

Systemic Analysis – County Highway Assessment for Metro


Implementation Guidance for State Highways

GOAL FOR METRO DISTRICT

Reactive Proactive

GOAL FOR GREATER MINNESOTA DISTRICTS50/50 GOAL

High-Cost Improvements

Moderate-Cost Intersection

Improvements

Corridor Management and Technology Improvements

Low-Cost Intersection Improvements

Road Departure Improvements

TurnLaneModifications

StreetLights

Channelization

RedLightEnforcement

EnhanceTrafficSignsandMarkings

CurbExtensions

Interchanges

RoadReconstruction

Roundabouts

After

Before

IndirectTurns

ImproveSightDistance

After

Before

ImproveTrafficSignalOperations

Accel/DecelLanes

EmployITSTechnologies

Elec.SpeedEnforcementinSchoolZones

AccessManagement

After

Before

RoadSafetyAudit

EnhancedDel.ofCurves

CableMedianBarrier

SafetyEdge

EdgeTreatments

PavedShouldersRumbleStrips/Stripes

UpgradeRoadsideHardware

Highlights • AspartoftheSHSP,MnDOTdeveloped

implementationguidanceforthedistricts.

• ThegoalfordistrictsinGreaterMinnesotaistohaveasafetyprogramthatisprimarilyfocusedonproactivelydeploying(relatively)low-costsafetystrategiesbroadlyacrosstheirsystemsofruraltwo-laneroadsandfreeways.

• ThegoalfortheMetropolitanDistrictistobaseitssafetyprogramprimarilyondeployinggenerallyhighercostsafetystrategiesatitssustainedhighcrashlocations,whilereservingafractionofitsresourcesforwidelydeployinglow-costnewtechnologiesorinnovationsacrossthesystem.

METRO DISTRICTMETRO DISTRICTGREATER MINNESOTA DISTRICTSGREATER MINNESOTA DISTRICTS


Highlights • Theprimaryobjectiveofthesafetyanalysisconductedaspartof

thecountyroadwaysafetyplanswastoidentifytheprimarycausesofseverecrashesandtoconductaprioritizationexerciselinkingat-risklocationswithashortlistofhighprioritysafetystrategies–theidentificationofsafetyprojectsthatarecandidatesforfundingthroughthestate’shighwaysafetyimprovementprogram.

• Thereviewofcountycrashdatafoundnosustainedhighcrashlocationsonthecountysystem,butdidfindapooloflife-changingcrashes(fatal+severeinjury)thatwouldbesusceptibletocorrection.

• Theanalysisfoundthemostfrequenttypesofseverecrashesinruralcountieswereroaddeparturecrashesalongsegmentsandhorizontalcurves,aswellasrightanglecrashesatThru/STOPcontrolledintersections.Intheurbancountiesthemostfrequentseverecrasheswererightangleandpedestrian/bicyclecrashesatsignalizedintersectionsandrear-endinsegments.

• Theprocessultimatelyidentifiedthefollowing:

• 16,500ruralroadedge,curvedelineation,andintersectionimprovementprojectsvaluedatmorethan$232M.

• 660urbansignalizedintersectionandroadwaysegmentimprovementsvaluedatapproximately$14M.

Implementation Guidance for County Highways

Street Lighting

Rumble Strips

Countdown Timers and Advanced Pedestrian Intervals

Dynamic Warning Signs

Red-Light Confirmation Lights


Highlights • Minnesota Toward Zero Deathsisaninterdisciplinarypartnershipwhichbeganin2003

withtheDepartmentofHealth,Transportation,andPublicSafety.

• Ourmissionistocreateacultureforwhichtrafficfatalitiesandseriousinjuriesarenolongeracceptablethroughtheintegratedapplicationofeducation,engineering,enforcement,andemergency medical and trauma services.Theseeffortswillbedrivenbydata,bestpractices,andresearch.

Success

• Interdisciplinarypartnership,groundwork,legwork,teamwork,educateonother“E”stobenefiteducationofalltrafficsafety.

• TrafficSafetycoalitions:www.minnesotatzd.org/initiatives/saferoads/coalition/

• Statewidegoalsoftrafficsafetycoalitions:

• Coalitionscanincludeindividualsaswellasrepresentativesofotherorganizations,suchaspolicedepartmentsoremergencyservicesproviders.

• Coalitionsareoftenmoreeffectivethanindividualsworkingalone-orevendifferentorganizationsworkingindependently.

• Coalitionscandevelopstrongerpublicsupportforanissuebyincreasingvisibilityandpublicawareness.

• WorkingtogetheristhefoundationoftheTowardZeroDeathsprogram.

Public Service

• Media

• Workplacepolicyandimplementation

• Parentcomponenttodriver’seducation

• HighVisibilityCampaigns–linktocalendar:https://dps.mn.gov/divisions/ots/law-enforcement/Pages/calendar.aspx

FindyourlocalTZDcoordinator:www.minnesotatzd.org/whatistzd/mntzd/contact/

Safety Planning at the Local Level

TZD Regions


Highlights • Federalhighwaylegislationrequiresallstatestopreparestrategicsafetyplans,andallofthestateshave

complied.

• Nationalcrashdataindicatebetween15%and60%oftrafficfatalitiesoccuronlocalroads(thenationalaverageis43%).Thisclearlyindicatestheneedforthestatestoengagelocalroadauthoritiesinstatewidestrategicsafetyplanningefforts.

• InMinnesota,almost65%ofcrashesinvolvingseriousinjuriesoccuronlocalroads.MnDOThassupportedsafetyplanningatthelocallevelbyincreasinglevelsoffinancialassistanceandtechnicalsupport.The2015-2016HighwaySafetyImprovementProgramallocatedalmost$10millionfor53projectsonthelocalsystem(includingprojectsthatinvolveenhancingtheedgeofruralroads,installingchevronsincurvesandaddingintersectionlighting).AlloftheseprojectswereidentifiedinplanspreparedforcountiesinMinnesotaaspartoftheMnDOTfundedCountyRoadwaySafetyPlans.

• Thesinglemostimportantpracticetosupportsafetyatthelocallevelisforagenciestodedicateapor-tionoftheircapitalimprovementprogramtoimplementinglow-coststrategiesontheirsystem.

• Inadditiontoimprovementstoroadways,otherlocalsafetybasedpracticescouldinclude:

• Initiating/participatinginSafeCommunitiesprogram

• Initiating/participatinginSafeRoutestoSchoolprogram

• Initiatingafatalcrashreviewprocessthatinvolveslawenforcementandengineeringstaffplusemergencyresponders

• Supportlawenforcementinitiativestoreducespeeding,improveseatbeltcomplianceandreducingdrinkinganddriving.AnexampleofahighlyeffectivelocallawenforcementinitiativeistheRiceCountyMODSquad.AteamconsistingofRiceCountysheriffs,theMinnesotaSatePatrolandlocalpoliceconductedahigh-visibilityenforcementcampaignto“MOD-ify”unsafedrivingbehavior.TheMODSquadtargetedsmallercommunitiesandlocalfestivalsandcelebrations.Inthe10yearspriortothehigh-visibilityenforcementcampaign,RiceCountyaveraged12alcohol-relatedfatalitiesperyear.Inthefirstyearofthecampaign,thenumberdroppedtozero.

Safety Planning at the Local Level

C-1Traffic Safety Fundamentals Handbook – 2015

C-2 Traffic Safety Tool Box – Then vs. NowC-4 Effectiveness of Safety StrategiesC-5 Safety Strategies

– HSIP Impact PyramidC-6 – CMF ClearinghouseC-8 – Highway Safety ManualC-10 – Highway Capacity ManualC-11 – Countermeasures that WorkC-12 – InfrastructureC-13 – BehaviorC-14 Roadside Safety InitiativesC-13 – Edge TreatmentsC-17 – Horizontal CurvesC-19 – Slope Design/Clear Recovery AreasC-20 – Upgrade Roadside HardwareC-21 Effectiveness of Roadside Safety InitiativesC-22 Addressing Head-On Collisions

C-24 Intersection Safety StrategiesC-25 Intersections

– Conflict Points – Traditional DesignC-26 – Conflict Points – New DesignC-28 – Enhanced Signs and MarkingsC-29 – Sight DistanceC-30 – Turn Lane DesignsC-31 – Roundabouts and Indirect TurnsC-32 – Traffic Signal OperationsC-33 – Red Light EnforcementC-35 Rural Intersections

– Safety Effects of Street LightingC-36 – Flashing BeaconsC-37 – Transverse Rumble StripsC-38 Pedestrian Safety StrategiesC-39 Pedestrian Safety

– Crash Rates vs. Crossing FeaturesC-40 – Curb Extensions and Medians

C-41 Pedestrian/Bike StrategiesC-42 Complete StreetsC-43 Neighborhood Traffic Control MeasuresC-44 Speed ZoningC-46 Speed Reduction EffortsC-47 Speed Zoning

– School ZonesC-48 Speed StrategiesC-49 Technology ApplicationsC-50 Impaired Driver StrategiesC-51 Inattention StrategiesC-52 Unbelted StrategiesC-53 Temporary Traffic Control ZonesC-55 Average Crash CostsC-56 Crash Reduction Benefit/ Cost (B/C) Ratio

WorksheetC-57 Typical Benefit/Cost Ratios for

Various Improvements

Traffic Safety Tool Box

C-1

Section C



Then

Now STOP

ONE WAY

Highlights

THEN:

• Onlyafewsourcesofinformationabouttheeffectivenessofsafetyprojectswereavailable,nonewerecomprehensiveandtherewereconcernsaboutthestatis-ticalreliabilityoftheconclusionsbecauseoftheanalyticaltechniquesthatwereused.Mostoftheinformationavailablewasbasedonobservationsofalimitednumberoflocations.

NOW: • Betterandmorecomprehensivesetofreferencesareavailable:

• NCHRPSeries500Reports–ImplementationofAASHTO’sStrategicHighwaySafetyPlan:http://safety.transportation.org/guides.aspx

• FHWA’sCrashModificationFactorClearinghousewww.cmfclearinghouse.org

• HighwaySafetyManual:www.highwaysafetymanual.org

Traffic Safety Tool Box – Then vs. Now


Engineering

• Trees in Hazardous Locations

• Head-On Crashes

• Unsignalized Inter-sections

• Run-Off-Road Crashes

• Pedestrians

• Horizontal Curves

• Signalized Intersec-tions

• Utility Poles

• Work Zones

Emergency Services

• Rural Emergency Medical Services

Highlights• TheNationalCooperativeHighwayResearchProgram

(NCHRP)developedaseriesofguidestoassiststateandlocalagenciesinreducingthenumberofseverecrashesinanumberoftargetedareas.

• Theguidescorrespondtothe22safetyemphasisareasoutlinedinAASHTO’sStrategicHighwaySafetyPlan(SHSP).

• Eachguideincludesadescriptionoftheproblemandalistofsuggestedstrategies/countermeasurestoaddresstheproblem.

• Thelistofstrategiesineachguidewasgeneratedbyanexpertpanelthatconsistedofbothacademicsandpractitionersinordertoprovideabalanceandafocusonfeasibility.

• Inadditiontodescribingeachstrategy,supplementalinforma-tionisprovided,includingthefollowing:

• Expectedeffectiveness(crashreductionfactors)

• Implementationcosts

• Challengestoimplementation

• Organizationalandpolicyissues

• DesignationofeachstrategyaseitherTried,Experimental,orProven

• http://safety.transportation.org/guides.aspx

Education

• Older Drivers

• Distracted/Fatigued Drivers

• Motorcycles

• Alcohol

Enforcement

• Aggressive Driving

• Unlicensed/Sus-pended/Revoked Drivers License

• Unbelted Occupants

• Heavy Trucks

Traffic Safety Tool Box – Then vs. Now


Effectiveness of Safety Strategies

Highlights• Trafficengineershavehistoricallyhada“toolbox”ofstrategies

thatcouldbedeployedtoaddresssafetyconcerns.Theresultsofrecentsafetyresearchstudiessuggestthattheprocessfororiginallyfillingthetoolboxappearstohavebeenprimarilybasedonanecdotalinformation.

• Therecentresearcheffortshavesubjectedanumberofsafetymeasurestoacomprehensivepackageofcomparativeandbeforevs.afteranalysesandrigorousstatisticaltests.Theresultsofthisresearchindicatethatsomesafetymeasuresshouldbekeptinthetoolbox,someremoved,somenewmeasuresadded,andsomecontinuedtobestudied.

• The22volumesthatmakeuptheNCHRPSeries500Reports–ImplementationofAASHTO’sStrategicHighwaySafetyPlan–identifyover600possiblesafetystrategiesincategoriesincludingdriverbehavior(speeding,safetybeltusageandalcohol),infrastructurerelatedimprovements(toreducehead-on,roaddeparture,andintersectioncrashes)andprovidingemergencymedicalservices.

• TheseNCHRPReportshavedesignatedeachofthestrategiesaseitherProven(asaresultofarigorousstatisticalanalysis),Tried(widelydeployedbutnostatisticalproofofeffectiveness),orExperimental(newtechniquesorstrategiesandnostatisticalproof).

• ItshouldbenotedthatvirtuallyallofthestrategiesthathavebeendesignatedintheNCHRPSeries500ReportsaseitherProven,Tried,orExperimentalareassociatedwithengineeringactivities.Thisisduetothelackofpublishedresearchquan-tifyingthecrashreductioneffectsofstrategiesdealingwitheducation,enforcement,andemergencyservices.

Educ

atio

nEn

gine

erin

gEn

forc

emen

t

• GraduatedDriversLicensing

• SafetyBeltEnforcementCampaigns

• DWICheckpoints

• StreetLightsatRuralIntersections

• AccessManagement

• RoadsideSafetyInitiatives

• Pave/WidenShoulders

• Roundabouts

• ExclusiveLeftTurnSignalPhasing

• ShoulderRumbleStrips

• ImprovedRoadwayAlignment

• CableMedianBarrier

• RemovingUnwarrantedTrafficSignals

• RemovingTreesinHazardousLocations

• PedestrianCrosswalks,Sidewalks,andRefugeIslands

• LeftTurnLanesonUrbanArterial

• RumbleStrips(ontheapproachtointersections)

• NeighborhoodTrafficControl(TrafficCalming)

• OverheadRed/YellowFlashers

• IncreasedLevelsofIntersectionTrafficControl

• IndirectLeftTurnTreatments

• RestrictingTurningManeuvers

• PedestrianSignals

• ImproveTrafficControlDevicesonMinorIntersectionApproaches

Engi

neer

ing

• TurnandBypassLanesatRuralIntersections

• DynamicWarningDevicesatHorizontalCurves

• Static/DynamicGapAssistanceDevices

• DelineatingTreesinHazardousLocations

• MarkedPedestrianCrosswalksatUnsignal-izedIntersections

Engi

neer

ing

ExperimentalProven Tried


Highlights• MnDOTcreatedavisualreferencetool,theHighway

SafetyImprovementProgram(HSIP)ImpactPyramid.

• TheHSIPImpactPyramidsuccinctlyshowstherelativebenefitsofvariousroadwaysafetymeasuresbygroupingindividualcountermeasuresinahierarchyoffour“impact”tiers.

• Thepyramidshowsthemostbeneficialstrategiesonthelargesttier(thepyramidbase/foundation)andnarrowstotheleastbeneficialitemsonthesmallesttier(thepinnacle).

• TheHSIPImpactPyramidreflectsMnDOT’spreferenceforsystemicHSIPimprovementsthatwillresultinthegreatestimpactstolocalroadwaysafety,whileacknowledgingthatreactivesite-specificmeasuresmustalsobeconsidered.

• Thistoolhashelpedlocalagenciesunderstandwhichimprovementsareeffective,selecteligibleprojects,andreducecrashpotentialonlocalroadways.

Safety Strategies – HSIP Impact Pyramid

FHWA, Noteworthy Practices: Addressing Safety on Locally Owned and Maintained Roads, A Domestic Scan, August 2010


Highlights• Themostcomprehensivesourceofinformationabouttheeffectiveness

ofthevarietyofSafetyStrategiesisFHWA’sCrashModificationFactorsClearinghouse(www.cmfclearinghouse.org)

• TheuseofaCrashModificationFactor(CMF)allowstheestimationofthelong-termchangesinthenumberofcrashesthatcanbeexpectedasaresultofimplementingaparticularstrategyataparticularlocation.

• ACMFisamultiplicativefactor–forexampleaCMF=0.8suggeststhattheimplementationofastrategywillreducecrashesto80%ofthehistoricvalue.ACMFof1.1suggeststhatimplementationwillincreasecrashesto110%ofthehistoricvalue.

• TheCMFClearinghousereportsbothCMFsandCRFs(CrashReductionFactors).TheCRFrepresentstheexpectedcrashreductionandtheCMFisafactorusedtoestimatetheexpectednumberofcrashesfollowingimplementationofaspecificstrategy.

• Thedatapresentedintheclearinghouseisbasedonpublishedresearchandisupdatedasnewreportsareaddedtothedatabase.

Safety Strategies – CMF Clearinghouse


Highlights• Theresultsreportedintheclearinghouseinclude:

• TheCMFandCRF

• Asubjectiveassessmentoftheresults(primarilybasedonthetypeofstatisticaltestingreportedintheresearch)

• IdentificationoftheCrashTypeandSeverity

• TheAreaType(ruralorurban)

• TheReference(sotheentirereportcanbereviewed)

• Thequalityassessmentinvolvesassigningbetweenzeroand5starstoeachCMFslisted,dependingonthetypeofstatisticaltestingconductedaspartoftheresearch.Aratingof5starsindicatesavigorousprogramoftestingandzerostarsindicatesnotesting.Theusercanselectthequalityofthereports,andthehighertherating,thehigherthelevelofconfidenceinthereportvalueoftheCMFs.

• ThistableofCMFsforEdgeLineRumbleStripsshows11values,rangingfroma43%reductionincrashestoa31%increase,withanaverageofa20%reduction.

Safety Strategies – CMF Clearinghouse


Highlights• TheHighwaySafetyManual(HSM)waspublishedbyAASHTOin2010inordertoprovide

professionalswithanalyticaltoolsandtechniquestoquantifythepotentialeffectsoncrashesasaresultofdecisionsmadeinplanning,design,operations,andmaintenanceofhighwaysystems.

• Akeypointisthenotionthatthereisnosuchthingasabsolutesafety–therearerisksassociatedwithallelementsofthesystem.

• TheobjectiveoftheHSMistohelppractitionersunderstandandbalancesafetyimplicationsoftrade-offsmadewhenassessingthepossiblesocial,economic,andenvironmentaleffectsidentifiedduringprojectdevelopment.

• TheHSMfocusesonhowtoestimatecrashfrequencyforaparticularroadwaynetwork,facilityorsiteinthegivenperiod–measuresof“objective”safety.Incontrast,subjectivesafetyconcernstheperceptionsofhowsafedriversfeelwhileonthesystem.Itshouldbenotedthatwhatmanydriversfeelisbasedontheirintuitionastowhatissafe.However,researchhasshownthatmanyelementsoftrafficsafetyarecounterintuitive.

• Driversbelievethattrafficsignalsaresafetydevicesbutthedataisconclusivethatsignalizedinter-sectionshavemore(andmoresevere)crashesthanunsignalizedintersections(evenwhennormalizedforvolume).

• DriversbelievethatmostdriversStopatSTOPsignsbutdataindicatesthatfewerthan20%do.

• Driversbelievethatmostdriversobeythepostedspeedlimitandthatlowerspeedsresultinfewercrashes.Thedataindicatesthatmostdriverswillviolateapostedlimitifitdoesnotapproximatetheactual85thpercentilespeedandcrashesaremorecloselycorrelatedwithaccessdensitythanspeed.

• ThepredictivemethodintheHSMusesSafetyPerformanceFunctions(SPFs)whichareregressionequationstoestimatetheaveragecrashfrequencyforaspecificsiteasafunctionoftrafficvolume,crosssectionandavarietyofothercharacteristics.TheHSMencouragesuserstocalibratetheSPFsfortheirsystem.ThishasbeendoneonpartsoftheTrunkHighwaysystembutnotonanylocalroad-ways.WithoutcalibrationtheHSMsuggestslimitingtheanalysistotherelativedifferencebetweenalternativesandnotsite-specificcrashfrequencies.

Safety Strategies – Highway Safety Manual


Highlights• Researchisunderwaytodocumentandquantifytherelationshipbetweenaroadway’sdesignfeatures

andsafetycharacteristics.Currentthinkingaboutthisrelationshipsuggeststherearetwodimensionsofsafety–NominalandSubstantive.

• Theconceptofnominalsafetyinvolvesacomparisonofthedimensionsofdesignfeaturestoanagency’sadopteddesigncriteria.Inthisconcept,aroadwayoraproposedsetofdesignfeaturesisconsideredtobenominallysafeifthefeaturesmeetorexceedtheminimumvalues.Nominalsafetyisanabsolute,thedesignfeatureseithermeettheminimumcriteriaortheydonot.

• Theconcernwiththisconceptisarecognitionthatthesafetyeffectsofincrementaldifferencesinagivendesigndimensionisexpectedtoproduceincrementalandnotabsolutechangeinsafety.Thenominalsafetyconceptislimitedinthatitdoesnotaddresstheactualorexpectedsafetyperformance.

• Substantivesafetyisdefinedastheexpectedlong-termsafetyperformance(crashfrequency,type,andseverity).

• TheHSMquantifiesthesesubstantivesafetyrelationshipswheretheyareknown.Forexample,agenciesaroundthecountryhaveworkedforyearstoachieve12-footlanewidthsalongruralroad-waysasawaytooptimizesafetyperformance.However,currentresearchindicatesthattheactualdifferenceincrashfrequencyis5%atvolumesgreaterthan2,000vehiclesperdayand1%atvolumesunder400vehiclesperday.

Safety Strategies – Highway Safety Manual

NCHRP Report 480 Transportation Research Board, 2002 FHWA – SA-07-011, Mitigation Strategies for Design Exceptions, 2007


Highlights• Recentresearchhasidentifiedarelationshipbetweentrafficsafetyandtraffic

operations,withcertaintypesofroadwaysexperiencinghighernumbersofcrashesaslevelsofcongestionincreases.

• TheHighwayCapacityManual(HCM)providesanalyticaltechniquestoassistengineersandplannersdocumentthequalityofthetrafficoperation(thelevelofcongestion)basedonsetofvariables,including;trafficcharacteristics,roadwaycharacteristicsandintersectioncontrols.

• Thecurrentedition(2010)isthefirstHCMtoprovideamultimodalapproachtotheanalysisandevaluationofurbanstreetsfromthepointofviewofdrivers,transit,bicyclistsandpedestrians.Thiseditionalsoprovidestoolsandgeneralizedservicevolumestoassistinsizingfuturefacilities.

• TheFederalHighwayAdministrationhasdevelopedanewtool–TheCapacityAnalysisforPlanningofJunctions(CAP-X)–thatcanbeusedtoevaluateavarietyoftypesofinnovativejunctiondesigns(eightintersections,fiveinterchanges,threeroundaboutsandtwomini-roundabouts).

• http://www.fhwa.dot.gov/software/research/operations/cap-x/

• Trafficoperationsanalysestosupportdesignlevelstudiesarebasedonpeaktrafficflows.However,anunder-standingoftherelationshipbetweentrafficvolumeandroadwaycross-sectioncanaddvaluetosystemplanningefforts.Toaidtheseplanningstudies,effortshavebeenmadetodevelopestimatesofthelevelofcongestionacrossgeneralizedroadwaytypesbasedondailytrafficvolumesandassumedvaluesfordetailssuchasthefractionofpeakhourtraffic,directionaldistribution,pedestriansandheavyvehicles.

Safety Strategies – Highway Capacity Manual

Note:Approximatevaluesbasedonhighlydependentassumptions.Donotuseforoperationalanalysesorfinaldesign.

Capacity Assumptions*

ThroughOnlyLane 800vphLT/THLane 600vphTH/RTLane 700vphTH/RT/FTLanes 600vphTurnLanes 350vph

*Assumes1/4milesignalspacing.Forlessthan1/4milesignalspacing,roadwaybecomestoovolatiletodetermineLOSbyADT.

Peak Hour Percentages

ArterialRoadway 10%

DirectionalOrientation 60/40

Planning Level Estimate of Level of Service (LOS)


Highlights• ThisguideisabasicreferencetoassistStateHighwaySafetyOffices

inselectingeffective,evidence-basedcountermeasuresforbehavioraltrafficsafetyproblemsareasincluding:

• Alcohol-impairedandDruggedDriving

• SeatBeltsandChildRestraints

• AggressiveDrivingandSpeeding

• DistractedandDrowsyDriving

• MotorcycleSafety

• YoungDrivers

• OlderDrivers

• Pedestrians

• Bicycles

• Theguidecontainsinformationoneachproblemareaincludingabriefoverviewoftheproblemarea’ssizeandcharacteristics,themaincountermeasurestrategies,alongwithatablethatlistsspecificcountermeasuresandsummarizestheireffectiveness,costs,use,andimplementationtime.

Safety Strategies – Countermeasures that Work


Highlights• ThesafetyplanpreparedforeverycountyinMinnesotafocusedon

maximizingtheuseofproveneffectivestrategies.TheuseofthesestrategiesprovidesboththesafetyprojectdevelopersandMnDOTsafetyprogrammanagersthehighestlevelofconfidencethattheproposedimplementationwillresultinsimilaroutcomesachievedbythedeploymentreportedinthepublishedliterature–aparticularcrashreduction.

• Thetableatleftdocumentsthe22basicsafetystrategiesthatwereusedinthedevelopmentoftheCountyRoadwaySafetyPlan.TwelveofthestrategieswereconsideredProveneffective,withCRFsgenerallyinthe20%to30%range.NineofthestrategieswereconsideredTried,withCRFsagaingenerallyaround30%.Onestrategy(theRCUTorchannelizedmedianintersection)wasconsideredExperimental–butinlimiteddeploymentinMinnesotaandaroundtheCounty,thisstrategyhasineachcaseresultedinavirtualeliminationofrightanglecrashes.

Safety Strategies – Infrastructure


Highlights• Thetablesatleftsummarizethebehaviorstrategiesfrom

Countermeasures that Work forbehavioralfocusareas.

• Cost to implement:

• $$$:requiresextensivenewfacilities,staff,equipment,orpublicity,ormakesheavydemandsoncurrentresources

• $$:requiressomeadditionalstafftime,equipment,facilities,and/orpublicity

• $:canbeimplementedwithcurrentstaff,perhapswithtraining;limitedcostsforequipment,facilities,andpublicity

• Theseestimatesdonotincludethecostsofenactinglegislationorestablishingpolicies.

• Use:

• High:morethantwo-thirdsoftheStates,orasubstantialmajorityofcommunities

• Medium:betweenone-thirdandtwo-thirdsofStatesorcommunities

• Low:lessthanone-thirdoftheStatesorcommunities

• Unknown:datanotavailable

• Time to implement:

• Long:morethanoneyear

• Medium:morethanthreemonthsbutlessthanoneyear

• Short:threemonthsorless

• Theseestimatesdonotincludethetimerequiredtoenactlegislationorestablishpolicies.

Safety Strategies – Behavior

Alc

ohol

Unb

elte

dIn

atte

ntiv

eSp

eed


Roadside SafetyInitiatives

Highlights• SinglevehicleroaddeparturecrasheshavebeenidentifiedasbeingoneofMinnesota’s

safetyfocusareas.

• Singlevehicleroaddeparturecrashesaccountfor32%ofallfatalcrashesinMinnesotaandasmuchas47%offatalcrashesonlocalroadsinruralareas.

• TheguidanceintheNCHRPService500Report–Volume6suggestsathree-stepprocessforaddressingroaddeparturecrashes:

1.Keepvehiclesontheroad

2.Provideclearrecoveryareas

3. Install/upgradehighwayhardware

• Thisthree-steppriorityisbasedoncostconsider-ations,feasibility,andlogic.Thestrategiesassociatedwithkeepingvehiclesontheroadaregenerallylowcost,caneasilybeimplementedbecauseadditionalright-of-wayanddetailedenvironmentalanalysesarenotrequired,andtreatingroadedgesdirectlyaddressestherootcauseoftheproblem–vehiclesstrayingfromthelane.

• Providingclearrecoveryareasisconsideredtobethesecondpriorityeventhoughthestrategieshavebeenproveneffective,becauseofimplantationchallenges–costsaregenerallyhigherthanforedgetreatments,andadditionalright-of-waymayberequiredaswellasamoredetailedenvironmentalreview.

• Installing/upgradinghighwayhardwareisthethirdprioritybecauseitcanbeexpensivetoconstructandmaintain,itcancauseinjurieswhenhit,anditdoesnotaddresstherootcauseoftheproblem.

Emphasis Area Objectives and StrategiesObjectives Strategies

15.1A–Keepve-hiclesfromencroach-ingontheroadside

15.1A1–Installshoulderrumblestrips15.1A2–Installedgeline“profilemarking,”edgelinerumblestrips,ormodifiedshoulderrumblestripsonsectionwithnarrowornopavedshoulders15.1A3–Installmidlanerumblestrips15.1A4–Provideenhancedshoulderorin-lanedelineationandmarkingforsharpcurves15.1A5–Provideimprovedhighwaygeometryforhorizontalcurves15.1A6–Provideenhancedpavementmarkings15.1A7–Provideskid-resistantpavementsurfaces15.1A8–ApplyshouldertreatmentsEliminateshoulderdrop-offsWidenand/orpaveshoulders

15.1B–Minimizethelikelihoodofcrash-ingintoanobjectoroverturningifthevehicletravelsofftheshoulder

15.1B1–Designsaferslopesandditchestopreventrollovers15.1B2–Remove/relocateobjectsinhazardouslocations15.1B3–Delineatetreesorutilitypoleswithretrore-flectivetape

15.1.C–Reducetheseverityofthecrash

15.1C1–Improvedesignofroadsidehardware(e.g.,lightpoles,signs,bridgerails)15.1C2–Improvedesignandapplicationofbarrierandattenuationsystems

NCHRP Report 500 Series (Volume 6)


Highlights• Typicaledgetreatmentsincludeshoulder/edgeline

rumblestrips,enhancedpavementmarkings,andeliminatingshoulderdrop-offs.

• Implementationcostsvaryfromlowcost(safetyedge)toseveralthousanddollarspermileforrumblestrips/stripEsandembeddedwetreflectivemarkings.

• Nationalsafetystudieshavedocumentedcrashreductionsintherangeof20%to50%forroaddeparturecrashes.

• Additionalbenefitshavebeenobservedonprojectswhereedgelineshavebeenpaintedovertheedgelinerumblestrips–nighttimevisibilityinwetpave-mentconditionswasimproved(thereflectivebeadsappliedtothenearlyverticalfaceoftherumblestripremainabovethefilmofwateronthepavementsurface)andthelifeofthepavementmarkingwasextended(snowplowscannotscrapeawaythebeadsontheverticalfaces).

• St.LouisCountyhasinstalled114milesofrumblestripsand82milesofrumblestripEsandhasdocumentedasubstantialreductioninpavementmarkingmaintenancecosts.

Without Safety Edge

With Safety Edge

Paved Shoulder and Rumble Strip

Rumble StripE

Roadside Safety Initiatives – Edge Treatments


Highlights• Theinstallationofedgerumblestripshasproventobeeffectiveatreducinglanedeparturecrashes,

themostfrequenttypeinGreaterMinnesota.

• Theyhavegeneratedcomplaintsaboutnoise,bicyclesafety,andaccommodatingfarmequipment.

• MnDOThasconductednoisestudiesthatindicaterumbleswillincreasenoiselevels,butnotbeyondestablishedthresholds.

• Toreducethechanceofbicycleshavingtotraversearumblestrip,MnDOThasadoptedtheuseofaninnovativedesignthatprovides12feetofsmoothpavementedgebetween48footsectionswithgrooves.Thisdesignprovidesbicyclistswiththeopportunitytomovefromthetravellanetotherefugeoftheshoulderwhenbeingovertakenbyavehiclewithouthavingtotraversetherumbles.

• Anotherstrategyforreducingthenumberofcomplaintsaboutnoiseistoconsiderboththevolumeoftrafficandthedensityofadjacentresidentialdevelopmentaspartofasystemicriskassessment.FocusingtheinstallationofedgerumblesonroadwayswithfewwidelyspacedhomeshasbeenusedsuccessfullybyanumberofcountiesinMinnesota.

• Ifaroadwaywithahighdensityofresidentialdevelopmentisidentifiedasapriorityforlanedeparturecrashes,considerationshouldbegiventosubstitutinganembeddedwetreflectiveedgelinefortheedgerumble.Theembeddedwetreflectiveedgelinewillprovideenhancednighttimewetpavementedgedelineationwithoutconcernsfortrafficnoise.Theonlydisadvantageoftheembeddedwetreflectivestrategyaresomewhathighcostandtheeffectonlanedeparturecrashesisnotyetknown.

• Anotheralternativetoaddressnoiseconcernsassociatedwithground-inrumblestripsiscurrentlybeinginvestigatedandinvolvestheuseofasinusoidalprofile.Initialtestsofthe“quiet”rumbleindicatetheyproducenoiselevelsintherangeof3to6decibelsbelowtheground-inrumblestrips.

Roadside Safety Initiatives – Edge Treatments


Highlights• Anumberofpreviouslypublishedresearchreportshaveidentifiedhorizontalcurves

asat-riskelementsorruralroadssystems,however,thedegreeofriskwasnotquantified.

• ArecentreportpreparedbytheTexasTransportationInstitute(TTI)(FHWA/X-07/0-5439-1)relatedactualcrashratesonruralroadstotheradiusofcurvature.Theresultsofthisresearchindicatethatthecrashrateoncurveswithradiigreaterthan2,500feetisapproximatelyequaltothecrashrateontangentsections.

• Oncurveswithradiiof1,000feet,thecrashrateistwicetherateontangentsandcurves;curveswithradiiof500feetareequaltothecrashrateontangentsections.

• Theanalysisofapproximately19,000horizontalcurvesalongruralcountyhighwaysinMinnesotafoundresultssimilartotheTTIresearch.Curveswithradiibetween500feetand1,200feetweremostat-risk.

• Curveswithradiiwithinthis500-to1,200-footrangeaccountedforapproximately50%ofcurvesbut70%ofsevereroaddeparturecrashes.Thesecurvesalsohadthehighestdensityofseverecrashes.

• Otherkeyfindingsinclude:

• Eventhough50%ofallsevereroaddeparturecrashesalongruralcountyhighwaysoccurinahorizontalcurve,95%ofthecurveshadNOseverecrashesduringa5-yearstudyperiod.

• 2%ofcurveshadONEseverecrash.

• ThereareNO“DeadMan’sCurve”–nocurveaveragedoneseverecrashperyear.

• Theaveragecrashdensitywas0.005severecrashes/curve/year.

• TheanalysisofhorizontalcurvesalongruralcountyhighwaysinMinnesotaidentifiedmorethan10,000curvesashighprioritycandidatesforsafetyimprovementbasedonthepresenceofparticularroadwayandtrafficcharacteristics.Thesuggestedsafetyimprovementateachofthesehighprioritycurvesinvolvedtheinstallationofchevronsandedgelinerumblestripsthathadanaveragecostofslightlymorethan$7,000percurve.

Roadside Safety Initiatives – Horizontal Curves

FHWA-X-07-0-5439-1

Minnesota County Road Safety Plans, Data 2007-2011


Highlights• InruralMinnesotathelocalroadsystemisagridof

north/southandeast/westsectionlineroads.Thisgridsystemresultsinnumerouslocationswherelocalroadsintersectwithpavedcountyroadsandstatehighwaysinhorizontalcurves.

• TheanalysisofhorizontalcurvesthatwasconductedaspartoftheCountyRoadSafetyPlansfoundthatcurvesthatcontainedanintersectionhadahighercrashfrequencythancomparablecurveswithoutanintersection.

• Thepresenceofanintersectioninacurvealsoproducesaconditioncalleda“visualtrap”causingadriveronthemajorroadtoseearoadwaycontinueonthetangentwhenthemajorroadactuallyturns.Theanalysisfoundthatcurveswith“visualtraps”haveahigherfrequencyofcrashesthancomparablecurveswithout.

Roadside Safety Initiatives – Horizontal Curves

• Theanalysisofruralintersectionsfoundthatinter-sectionsincurveshadahigherfrequencyofcrashesthancomparableintersectionslocatedontangentsections.Itappearsthatcloselyspacedintersectionwithskewedapproachestothemajorroadincreasetheriskforintersectioncrashes(seefiguretotheleft).Thepreferredsolutionforimprovingthemultipleintersectioncurveinvolvedreconstructingtoprovideasingle“T”intersectionwheretheminorlegisper-pendiculartothemajorroad.

• Beyondtheuseoftypicallowcostimprovements,suchaschevronsandedgelinerumblestrips,addi-tionaldesignstrategiescouldbeprovidingstrategi-callyplacedvegetationtoaddressthe“visualtrap”issueandpossiblyreplacingthesinglehorizontalcurvewithtwocurvesseparatedbyatangentsection.

• Thepreferredsolution,reconstructingtheroadways,isnotalow-costsolutionandwouldlikelynotbeacandidateforsafetyfunding.

Example of a Visual Trap

Visual Trap

Visual Trap Solution


Highlights• Effortstoimproveclearzonesareusuallypartofreconstructionprojectsbecauseofhigher

costsassociatedwithflatteningslopesandreconstructingditches.Otherroadsideelementstypicallyaddressedasanintegralpartofreconstructioninclude:treeremoval,flatteningslopesatdrivewaysandfieldentrances,removingunnecessaryentrances,relocatingutilitypoles(iftheright-of-wayiswideenough)andupgradingroadsidehardware.

• Therecommendedclearzonedistanceisafunctionofspeed,slope,volume,andhorizontalcurvature.

• Generally,higherspeeds,steeperfillslopes,highervolumes,andlocationsalongtheoutsidesofhorizontalcurvesrequirelargerclearzones.

• Theconceptofprovidingclearrecoveryareasisprimarilyintendedforruralroadways.However,theconceptcanbeappliedtosuburbanorurbanroadwaysifroaddeparturecrashesareaconcern.

MnDOT Road Design Manual

Roadside Safety Initiatives –Slope Design/Clear Recovery Areas

Slope Design


Highlights• Upgradingroadsidehardwareistypicallyapartofongoinghighwaymaintenanceand

reconstructionprograms.Projectstoupgradetrafficsignsshouldaddresssignposts.Allsignpostslocatedintheclearzoneonroadswithspeedlimitsgreaterthan50milesperhourarerequiredtohaveabreakawaydesignorbeprotectedbyabarrierorcrashcushion.Guard-railsaretypicallyinstalledorupgradedaspartofhighwayreconstructionprojects.Itshouldbenotedthattheuseofguardrailsaretypicallyreservedforhighervolumeroadways(over400vehiclesperday)duetothehighcostofinstallationplusongoingmaintenance.

• Allhighwayhardwaremustmeettherequirementsin2009theAASHTOManualforAssessingSafetyHardware(MASH).

• Typicaltreatmentsandtheirinstallationcostsincludethefollowing:

• Impactattenuator=$20,000

• Guardrailterminal=$1,500

• Guardrailtransition=$1,000

• CableorW-BeamGuardrail=$75,000-$150,000permile

• Itisconsideredabestpracticetoupgraderoadsidehardwareasapartofreconstructionprojectsbecauseofsafetybenefitsassociatedwithreducingtheseverityofcollisionswithstructuresthatagenciesinstallalongroadedges,includingsignposts,mailboxsupports,andguardrails.However,itshouldbenotedthateffortsfocusedononlyupgradinghardware(asopposedtoalsoimprovingroadedgesandclearzones),whilenominallyaddressingsafetywouldbeexpectedtoprovidealimitedincreaseinsubstantivesafetybecauseoftherelativelyfewreportedcrasheswiththesetypesofstructures.

Roadside Safety Initiatives – Upgrade Roadside Hardware

Exampleimplementationscompliant(above)andnotcompliant(below)withcurrentstandards(NCHRP350)

Compliant

Noncompliant


Effectiveness of Roadside Safety Initiatives

Highlights• Anestimateofthesafetyimplicationsbyevaluatingtwovery

similarsegmentsoftwo-laneruraltrunkhighwaysinnorthernMinnesota:TH6andTH38.

• Bothroadshavethefollowingsimilarcharacteristics:• Havelowvolumes• Servesimilarfunctions(recreationalandlogging)• TraversetheChippewaNationalForest• Havescenicqualities

• In2008,TH6hadbeenreconstructedandTH38hadnot.(Note:ThissegmentofTH38hasrecentlybeenreconstructedbutaBeforevs.AfterStudyhasnotbeencompleted.)

• ThedifferencesincrashcharacteristicsTH38hadaresubstantial:• Morethantwiceasmanycrashes• Morethantwiceasmanyinjuries• Acrashratemorethantwicetheaveragefortwo-lanerural

roads(and30%greaterthanthecriticalrate)• AlmostfourtimesasmanySVRDcrashes(andmorethan

threetheaverageforsimilarroads).• Tentimesasmanytreehits• Morethantwiceasmanynighttimecrashes

• TH38hassincebeenreconstructedandthecrashreductionhasbeensubstantial–almost80%reductioninthenumberandrateofcrashes.TH38nowhassafetycharacteristicsbelowthenormsforsimilarroadways.

• Duringthesametimeperiod,TH6alsoexperiencedacrashreductionconsistentwithstatewidetrendsandcontinuestooperatewithinthetypicalrangefortwo-laneruralroadways.

PDO PropertyDamageOnlyVPD VehiclesPerDay


NOW THEN NOW11.2 11.2 Length (Miles) 11.2 11.2

9 23 Total Crashes (5 Years) 51 10

3 11 PDO Crashes 25 5

5 12 Injury Crashes 26 5

1 0 Fatal Crashes 0 0

575 1,100 Volume (VPD) 1,100 1,200

11.75 22.48 MVM 22.48 24.53

0.8 1.0 Crash Rates (Crashes/MVM) 2.3 0.4

1.5 1.5 Severity Rate 4.1 0.7

1.0 1.3 Critical Crash Rates 1.3 0.9

3 (33%) 10 (43%) SVRD Crashes 37 (73%) 8 (80%)

2 3 Hit Trees 30 3

0 8 (35%) Passing Crashes 3 (6%) 0

4 2 Angle Crashes 4 1

2 6 Deer Hits 1 1

0 10 (43%) Night 21 (41%) 4 (40%)

MVM MillionVehicleMilesSVRD SingleVehicleRoadDeparture

TH 6 TH 38


Highlights• Head-oncrashesaccountforapproximately20%ofthetrafficfatalities

inMinnesota.

• Addressinghead-oncrashesisoneofMinnesota’scriticalsafetyfocusareas.

• Minnesotaaveragesapproximately120fatalhead-oncrashesperyear,97%areNOTpassingrelatedontwo-lanefacilities,63%areonthestatesystem,andabout75%areinruralareas.

• Centerlinerumblestripshavebeenfoundtoreducehead-oncrashesalongtwo-laneroads–datafrom98sitesinsevenstates(includingMin-nesota)indicatedsignificantreductionsforinjurycrashes(15%)aswellasforhead-onandopposingsideswipeinjurycrashes(25%).

• Additionalstrategiesfortwo-laneroadsincludeconductingfieldsurveystoconfirmthatdesignatedpassingzonesmeetcurrentguidelinesforsightdistanceandtheuseofthermoplasticmarkingswherepassingisnotpermitted.

• Theconstructionof“PassingLanes”alongtwo-laneroadshasbeenfoundtobeaconvenienceformotorists(providingopportunitiestopassslowermovingvehicles).However,thereisnoevidencethatthepassinglaneshavereducedhead-oncrashes.

• Anumberofstateshavebeguntoaddresscross-medianhead-oncrashesondividedhighwaysbyinstallingcablemedianbarriers.Reportedreductionsinseverehead-oncrasheshaverangedfrom70%to95%.

• MnDOThasinstalledapproximately450milesofcablebarrier,withplanstoinstallanadditional80miles.ApreliminaryanalysisofMnDOT’sfirstcablemedianbarrierinstallation(alongI-94inMapleGrove)founda100%reductioninfatalitiesanda90%reductioninoverallcrashseverity.

NCHRP 500 Series (Volume 4)

Head–On Crashes on a Two–Lane Rural Highway in Delaware

Before and After Use of Centerline Rumble Stripe

SeverityofCrash

Head–OnCrashFrequency

36MonthsBefore 24MonthsAfter

Fatal 6 0

Injury 14 12

DamageOnly 19 6

Total 39 18

CrashesperMonth 1.1 0.76

AASHTO, “Driving Down Lane Departure Crashes”, April 2008

Fatal Head-On Crashes on Rural Two-Lane Two-Way High-ways in Minnesota, Derek Leuer, MnDOT, January 2015

Addressing Head-On Collisions

Interstate Cross-Median Fatalities

I-44 Cross-Median Fatalities


Highlights• Arecentlocalstudyoneffectsofcenterlinerumble

stripsonover200milesofruralroadwaysinMinne-sotafound40%to76%reductioninencroachmentsanda73%lowerfatalandseverecrashratesand42%lowercrashrateoverallthanlocationswithoutcenterlinerumbles.

• AnadditionalstudytodetermineifcenterlinerumblestripscontributetomotorcyclecrashesornegativelyaffectmotorcycleriderbehaviorwasconductedbyMnDOTin2008.Thestudyanalyzedcrashdataandobservationsfromaclosed-circuitcoursewith32ridersofvariousmotorcycletypes.

• Theclosed-circuitcourseobservationsshowednosteering,braking,orthrottleadjustmentduringstripcrossingsbytheriders.Inpost-circuitinterviews,noriderdescribedthestripsasahazard.

• Outofover9,000motorcyclecrashesreviewed,only29occurredatlocationswithrumblespresent.Noneofthecrashreportsmentionrumblestripsasafactor.

Addressing Head-On Collisions

Safety Effects of Centerline Rumble Strips in Minnesota(www.lrrb.org/media/reports/200844ts.pdf)

Effects of Centerline Rumble on Motorcycles: NCHRP 641 226(www.lrrb.org/media/reports/200807TS.pdf)


Intersection Safety StrategiesObjectives Strategies

Relative Cost to Implement and Operate

EffectivenessTypical Timeframe for Implementation

A-Improveaccessmanagement

A1-Implementintersectionordrivewayclosures,relocations,andturningrestrictionsusingsigningorbyprovidingchannelization.

LowtoModerate Tried Medium(1-2yrs)

B-Reducethefrequencyandseverityofinter-sectionconflictsthroughgeometricdesignimprovements

B1-Provideleft-turnlanesatintersections;providesufficientlengthtoaccommodatedecelerationandqueuing;anduseoffsetturnlanestoprovidebettervisibilityifneeded.

ModeratetoHigh

Proven Medium(1-2yrs)

B2-ProvidebypasslanesonshouldersatT-intersections. Low Tried Short(<1yr)

B3-Provideright-turnlanesatintersections;providesufficientlengthtoaccommodatedecelerationandqueuing;useoffsetturnlanestoprovidebettervisibilityifneeded;andprovideright-turnaccelerationlanes.

ModeratetoHigh

Proven Medium(1-2yrs)

B4-Realignintersectionapproachestoreduceoreliminateinter-sectionskew.

High Proven Medium(1-2yrs)

C-Improvedriverawarenessofintersectionsasviewedfromtheinter-sectionapproach.

C1-Improvevisibilityofintersectionsbyprovidingenhancedsigning.Thismayincludeinstallinglargerregulatory,warning,andguidesigningandsupplementarystopsigns.

Low Tried Short(<1yr)

C2-Improvevisibilityofintersectionsbyprovidinglighting(installorenhance)orredflashingbeaconsmountedonstopsigns.

LowtoModerate Proven Medium(1-2yrs)

C3-Improvevisibilityofintersectionsbyprovidingenhancedpave-mentmarkings,suchasaddingorwideningstopbaronminor-roadapproaches,supplementarymessages(i.e.,STOPAHEAD).

Low Tried Short(<1yr)

C4-Improvevisibilityoftrafficsignalsusingoverheadmastarmsandlargerlenses.

Moderate Tried Short(<1yr)

C5-Deploymainlinedynamicflashingbeaconstowarndriversofenteringtraffic.

Low Experimental Short(<1yr)

D-Improvesightdistanceatintersections.

D1-Clearsighttrianglesapproachestointersections;inadditiontoeliminatingobjectsintheroadside,thismayalsoincludeeliminatingparkingthatrestrictssightdistance.

LowtoModerate Tried Short(<1yr)

E-Chooseappropriateintersectiontrafficcontroltominimizecrashfrequencyandseverity

E1-Provideall-waystopcontrolatappropriateintersections. Low Proven Short(<1yr)

E2-Provideroundaboutsatappropriateintersections. High Proven Long(>2yrs)

F-Improvedrivercompliancewithtrafficcontroldevicesandtrafficlawsatintersections

F1-Enhanceenforcementofred-lightrunningviolationsusingauto-matedenforcement(cameras)oraddingconfirmationlightsonthebackofsignalstoassisttraditionalenforcementmethods.

Moderate Proven/Tried Medium(1-2yrs)

G-Reducefrequencyandseverityofintersectionconflictsthroughtrafficsignalcontrolandopera-tionalimprovements.

G1-Employmultiphasesignaloperation,signalcoordination,emer-gencyvehiclepreemptionoptimizeclearanceintervals;implementdilemmazoneprotection;onhighspeedroadways,installadvancewarningflasherstoinformdriverofneedtostop;andretimeadjacentsignalstocreategapsatstop-controlledintersections.

LowtoModerate Proven/Tried Medium(1-2yrs)

MnDOT Strategic Highway Safety Plan, 2014

Highlights • AddressingcrashesatintersectionsisoneofMinnesota’ssafety

focusareas.

• Intersection-relatedcrashesaccountformorethan50%ofallcrashesandaboutone-thirdoffatalcrashes.

• Approximatelytwo-thirdsoffatalintersectioncrashesoccurinGreaterMinnesotaandslightlymorethanone-halfareonthelocalsystem.

• STOP-controlledintersectionsaverageslightlylessthanonecrashperyearandsignalizedintersectionsaveragealmostsevencrashesperyear.

• Thehigh-prioritysafetystrategiesforunsignalizedintersectionsinvolvemanagingaccessandconflicts,enhancingsignsandmarkings,improvingintersectionsightdistance,andprovidingroundabouts.

• Thehigh-prioritystrategiesforsignalizedintersectionsincludereducingredlightviolationsandoptimizingsignaloperations.

• Onthestatesystem,about55%ofintersectioncrashesoccuratlocationswithSTOPcontrol.However,thereareseventimesasmanySTOP-controlledascomparedtosignal-controlledintersections.

• Thedensityofseverecrashes(Fatals&AInjuries)isfourtimeshigheratsignalizedintersectionsthanatSTOP-controlledintersections.

• MnDOThasdevelopedatooltoassisthighwayagencieswithchoicesaboutintersectioncontrol.TheIntersectionControlEvaluation(ICE)guidelinesprovidesdirectionsandrecom-mendationsforanobjectiveanalysisofsafetyandtrafficoperationsperformancemeasuresforavarietyofalternativecontrolstrategieswiththegoalofhelpingagenciesdeterminetheoptimalintersectioncontrolforagivensetofroadwayandtrafficconditions.


Intersections – Conflict PointsTraditional Design

Highlights • Areviewofthesafetyresearchsuggeststhatintersectioncrashratesare

relatedtothenumberofconflictsattheintersection.

• Conflictpointsarelocationsinorontheapproachestoanintersectionwherevehiclepathsmerge,diverge,orcross.

• Theactualnumberofconflictsatanintersectionisafunctionofthenumberofapproachinglegs(“T”intersectionhavefewerconflictsthanfour-leggedintersections)andtheallowedvehiclemovements(inter-sectionswhereleftturnsareprohibited/preventedhavefewerconflictsthanintersectionswhereallmovementsareallowed).

• Apreliminaryreviewofintersectioncrashdataindicatestwokeypoints:

• Somevehiclemovementsaremorehazardousthanothers.Thedataindicatesthatminorstreetcrossingmovementsandleftturnsontothemajorstreetarethemosthazardous(possiblybecauseoftheneedtoselectagapfromtwodirectionsofoncomingtraffic).Leftturnsfromthemajorstreetarelesshazardousthantheminorstreetmovements,andright-turnmovementsaretheleasthazardous.

• Crashratesandthefrequencyofseriouscrashesaretypicallyloweratrestrictedaccessintersections(3/4designandrightin/out)thanatsimilar4-leggedintersections.Prohibiting/preventingmovements(especiallythecrossingmovement)atanintersectionwilllikelyresultinasubstantialcrashreduction.

• Minnesotacrashdataclearlysupportsthenotionthatreducingconflicts,especiallycrossingconflicts,isassociatedwithareductionincrashes.Equivalentinformationabouttheeffectsoncrashseverityhasnotbeengenerated.However,itappearsreasonabletoassumethatanyeffortthatpreventscrossingmaneuversthatcontributetorightanglecollisionsshouldalsoreduceseverityofanyremainingcrashes.

Crossing TurningMerge/ Diverge Total

Typical Crash Rate(crashespermil.enteringvehicles)

FullAccess 4 12 16 32 0.7

FullAccessT 0 3 6 9 0.4

3/4Access 0 2 8 10 0.5

RightIn/OutAccess 0 0 4 4 0.2

Full AccessFull Access

Right In/Out Access

3/4 Access

2013 MnDOT Crash Data Toolkit

Crossing

Turning

Merge/Diverge

Pedestrian


Highlights • Analysisofcrashdataprovesthatthemostfrequenttypeofsevereintersectioncrash

isarightangle–vehiclemaneuversthatinvolvecrossingconflicts.

• Inresponsetothisdata,highwayagenciesarebeginningtoimplementintersectiondesignsthatreduceoreliminatetheat-riskcrossingmaneuversbysubstitutinglower-riskturning,merginganddivergingmaneuvers.Twoexamplesofthesenewdesignsincluderoundaboutsandindirectturntreatments.

• TheconceptofindirectturnshasprimarilybeenappliedtodividedroadwayswherethereissufficientroominthemediantoconstructthechannelizationnecessarytorestrictcrossingmaneuversandtoaccommodateU-turns.Thisdesigntechnique

Indirect Left Turn Access



FullAccess 4 12 16 32 0.7(1)

IndirectLeftTurn 0 4 20 24 0.1(2)

(1)2010-2012ruralMNstatehighwayintersectioncrashdata (2)EstimatedbasedonalimitedsampleofMnDOTdata

Intersections – Conflict PointsNew Design

Full Access

Crossing

Turning

Merge/Diverge

Pedestrian

hasbeenimplementedatapproximatelyadozenintersectionsinMarylandandNorthCarolinaand,asaresult,isconsideredTried.However,before/afterstudiesattheselocationshavedocumentedclosetoa90%reductionintotalcrashesanda100%reductioninanglecrashes.MoreinformationaboutindirectturnscanbefoundinReport650:Median Intersection Design for Rural High Speed Divided Highways.MinnesotahasnowconstructedtheindirectleftturndesignatexpresswayintersectionsalongTH36,TH53,TH65,TH71,TH169andTH212.Follow-upevaluationsfoundoverallcrashreductionsofapproximately75%anda100%reductioninbothangleandseriousinjuries.



Highlights • Roundaboutshavebeenimplementedatasufficientnumber

ofintersectionsinMinnesotaandaroundthecountry,suchthatfollow-upstudieshavedocumentedaProveneffective-nessofreducingboththefrequencyandseverityofcrashes.MoreinformationregardingroundaboutscanbefoundinRoundabouts: An Informational Guide(ReportNo.FHWA-RD-00-067)atwww.tfhrc.gov/safety/00-0675.pdf.

• Basedontheobservedsafetyandoperationalbenefitsdocumentedatsinglelaneroundabouts,highwayagencieshavebeguntoimplementmulti-laneroundaboutsatseveralhigh-volumeintersectionstoreplacetraditionaltrafficsignalcontrol.Studiesoftheseinstallationsindicatethat,similartosinglelaneroundabouts,multi-laneroundaboutsimprovetrafficoperationsandreduceintersectiondelay.However,ithasbeendeterminedthatmulti-laneroundaboutshaveagreaternumberofconflictsthansinglelanedesign(currentresearchhasnotbeenabletoagreeontheexactnumber)andthisappearstohaveresultedinanincreaseinthenumberofpropertydamageandminorinjurycrashesandhaveacrashratealmosttwicetheaverageforhighvolume/lowspeedsignal-controlledintersectionsinMinnesota.

• ResearchdocumentedinFHWA’sCMFClearinghouseisconsistentwithMinnesota’sexperiencewithconflictreductioneffortsresultingincrashreduction.TheCMFClearinghouseindicatestheconversiontoasinglelaneroundabouthasacrashreductionfactor(CRF)intherangeof25%to65%forallseveritiesandapproximately85%forseverecrashes.Thisresearchalsoindicatesthatconversiontoamulti-laneround-abouthasresultedinanoverallincreaseincrashesbuttheCRFforseverecrashesisstillintherangeof60%to70%.



FullAccess 4 12 16 32 0.7(1)

SingleLaneRoundabout 4 0 16 20 0.3(3)

Multi-LaneRoundabout N/A N/A N/A N/A 1.4(3)

(1)2010-2012ruralMNstatehighwayintersectioncrashdata.

(3)EstimatedbasedonalimitedsampleofMnDOTdata

(2)NCHRP15–30PreliminaryDraft

Multi-Lane Roundabout

Single Lane Roundabout Access

Full Access Typical Crash Rate 0.7 – Average crash rate for high volume/low speed signalized intersection

Note:Countofconflictsindispute,althoughtherearemany.

N/A–NotAvailable

Full Access

Crossing

Turning

Merge/Diverge

Pedestrian


Intersections – Conflict PointsNew Design


Highlights • ThemostcommontypeofcrashatSTOP-controlled

intersectionsisarightanglecrash.

• ResearchperformedinMinnesota(Reducing Crashes at Controlled Rural Intersections – MnDOT No. 2003-15)foundthatapproximately60%oftheseanglecrashesinvolvedvehiclesontheminorroadstoppingandthenpullingoutand26%involvedvehiclesrunningthroughtheSTOPsign.

• Thissamestudyalsofoundthatincreasingtheconspicuityoftrafficcontroldevicesbyusingbigger,brighter,oradditionalsignsandmarkings(suchastheSTOPAHEADmessageandaSTOPbar)areasso-ciatedwithdecreasingRuntheSTOPcrashes.

• Amorerecentreport,Safety Evaluation of STOP AHEAD Pavement Markings(FHWA-HRT-08-043),documentstheeffectsofaddingSTOPAHEADpavementmarkings.Thestudylookedat175sitesinArkansas,Maryland,andMinnesota.Thestudyfoundcrashreductionsintherangeof20%to40%,benefit/costratiosgreaterthan2to1,andconcludedthatthisstrategyhasthepotentialtoreducecrashesatunsignalizedintersections.1. Stop bar

2. Stop sign

3. Junction sign

4. Stop Ahead Message

5. Stop Ahead Sign

Intersections – EnhancedSigns and Markings

Mn MUTCD

Prioritized/ Phasing


Intersections – Sight Distance

Highlights• Intersectionsightdistancereferstothelengthofthegapalongthemajor

roadwaysufficienttoallowaminorstreetvehicletoeithersafelyenterorcrossthemajortrafficsystem.

• Areasonableintersectionsightdistanceallowsforadequatedriverper-ceptionreactiontime(2.5seconds)andeithersufficienttimetoclearthemajorstreet,ortoturnontothemajorstreetandacceleratetotheoperatingspeedwithoutcausingapproachingvehiclestoreducespeedbymorethan10mph.

• Theactuallengthoftherecommendedintersectiondistanceisafunctionofthemajorstreetoperatingspeed.However,thedesiredsizeofthegapvariesfrom7secondsat30mphto10secondsatspeedsof60mphandabove.

• WhendealingwithMnDOT’strunkhighways,refertoSection5-2.02.02oftheRoad Design Manualforadditionalguidanceregardingintersectionsightdistance.

• Itisimportanttonotethatintersectionsightdistanceisalwaysgreaterthanstoppingsightdistance,byasmuchas30%to60%.

• The10-second“RuleofThumb”–10secondsofintersectionsightdistance–isagoodestimate,regardlessofconditions.

• Removalofvegetationandon-streetparkingarecost-effectivesafetyimprovementsforintersections.

NCHRP Report 383 - Intersection Sight Distance Iowa Highway Safety Management System, and AASHTO Green Book

Adequate Sight Distance

Inadequate Sight Distance


Highlights • ProvidingrightandleftturnlanesatintersectionsareincludedinMinnesota’slist

ofhighprioritystrategies.

• However,therearelocationswherevehiclesarestoppedordeceleratingintheturnlaneandcanblockthelineofsightforothervehicleswaitingattheinter-sections.Inthesecases,theuseofoffsetleftandrightturnlaneswillimprovethelineofsightforvehicleswaitingtocompletetheircrossingorturningmaneuvers.

• OffsetturnlanesareconsideredTried(asopposedtoProven).Abefore/afterstudyofoffsetleftturnlanesinNorthCarolinareporteda90%reductioninleftturncrashes.AsimilarstudyofoffsetrightturnlanesinNebraskafounda70%reductioninnear-siderightanglecrashes.

• TheMedianAccelerationLane(MAL)hasbeenusedatanumberoflocationsinMinnesotaandisalsoconsideredTried.Before/afterstudiesindicatea75%reductioninsamedirectionsideswipecrashes,a35%reductioninfar-siderightanglecrashes,anda25%reductioninvolvingleftturncrashesfromtheminorroad.

• Turnlanelength–newreport#2010-25,Base Turn Lane Length on Analysis of Deceleration and Storage Demand.

NCHRP 15-30 Preliminary Draft

Intersections – Turn Lane Designs

OFFSET Left-Turn Lane

OFFSET Right-Turn Lane

Median Acceleration Lane

B. Tapered

A. Parallel


Minnesota Trunk Highway 13

at Scott County Highway 2

MnDOT Metro District Before: After Study

Highlights • ThemostcommonandmostseveretypeofcrashatSTOP-controlledintersectionsisarightangle

whichinvolvesavehicleontheminorroadattemptingtoselectasafegapalongthemajorhighwayinordertocross.

• Aprovenstrategytoreducegapselection-relatedanglecrashesinvolvesredesigningtheintersectionormediancrossovertoeliminatecrossingconflicts(whichhavethehighestprobabilityofacrash)bysubstitutingmerging,diverging,orturningconflicts(whichhavealowerprobabilityofacrash).

• Theprimaryexamplesofreduced-conflictdesignsatfour-leggedintersectionsincluderoundaboutsandindirectturns.

• RoundaboutsareconsideredtobeProveneffective(thereisvirtuallynopossibilityofananglecrash)withstatisticallysignificantcrashreductions–38%forallcrashes,and76%forinjurycrashesandforseriousinjuryandfatalcrashes.Notwithstandingthesuperiorsafetyperformance,caremustbetakenwhenconsideringconversiontoaroundabout–implementationcostsareintherangeof$1,000,000(rural)to$5,000,000(urban)andallenteringlegsaretreatedequally.Thekeyquestionisdothetrafficcharacteristicsandfunctionclassificationsupportthedegradingofmain-linetrafficoperations.

• Theconceptbehindindirectturnsisthatmerge,diverge,andturningconflictsresultinfewerandlessseverecrashesthancrossingconflicts.AnexampleoftheindirectturnappliedtoadividedroadwayistheJ-turn.Thisapplicationinvolvesconstructingabarrierinthemediancrossoverandforcingminorstreetcrossingtraffictoinsteadmakearightturn,followedbyadownstreamU-turn,followedbyanotherrightturn.J-turnshavebeenTriedataboutadozenlocationsinMarylandandNorthCarolina.Implementationcostsareintherangeof$500,000to$750,000,andapreliminarycrashanalysisfounda100%reductioninanglecrashesanda90%reductionintotalcrashes.

• AtTintersectionsthreenewdesignconceptshavebeendeveloped:thepartialT-interchange,thecontinuousgreenT,andthedivergingdiamondinterchange.

• ThepartialinterchangeisaninterestingconceptforTintersectionsalongdividedroadways–theconstructionofonebridgeonthe“near-side”oftheintersectioneliminatesallcrossingmaneuvers.ThisconceptisbeingconsideredforseverallocationsinMinnesota,butdeploymenthasnotbeensufficientlywidespreadtobeabletoidentifytypicalimplementationcostsordocumentcrashreductions.

NCHRP 15-30

Intersections – Roundaboutsand Indirect Turns

Photo provided by TKDA

Indirect Turns

Partial T-Interchange


Highlights • InstallingtrafficsignalsisNOTconsideredtobeahighpriorityinter-

sectionsafetystrategybecauseoftheresultsofstudiesdonenationallyandinMinnesota.Atmostintersections,theinstallationofatrafficsignalwillincreasethenumberofcrashes,alongwithincreasingcrashandseverityrates.Also,asacategory,signalizedintersectionshaveahigheraveragecrashdensity,crashrate,andseverityratethantheaverageforSTOP-controlledintersections.

• However,ifatrafficsignalmustbeinstalledtoaddressintersectiondelayandcongestion,thereareseveralsuggestedhighprioritystrategiestoreducefrequencyandseverityofintersectioncrashes.Theseinclude:

• Useofmultiphasesignaloperationcombinedwithleftturnlanes

• Provideacoordinatedsignalsystemalongurbanarterials

• Useoverheadindications–oneperthroughlanemountedatthecenterofeachlane

• Providedilemmazoneprotectionandoptimizeclearanceintervals

• Useadvancewarningflasherstosupplementstaticsignswhereasignalmaybeunexpected

• Pedestrianindicationsincludingtheuseofcountdowntimers

Intersections – Traffic Signal Operations


Highlights• RedLightRunning(RLR)isasafetyissueacrossthecountry.In2009,RLRresulted

in676trafficfatalities(10%ofallintersection-relatedfatalities).Inaddition,theInsuranceInstituteforHighwaySafetyestimatesthat130,000peoplewereinjuredincrashesin2009duetoRLR.

• RLRhasalsobeenfoundtobeanimportantsafetyissueinMinnesota.IntheMinneapolis-St.PaulMetropolitanArea,approximately60%ofseverecrashesareintersectionrelated,approximately50%ofthoseoccuratintersectionscontrolledbytrafficsignals,andalmostone-halfoftheseinvolvearightanglecollision.

• Inthemetropolitanarea,thenumberofsevererightanglecrashesvariesamongstate,countyandcityintersections,butonefactisconsistent–alongeachsystem,rightanglecrashesresultinmorefatalitiesandseriousinjuriesthanrear-end,left-turnandright-turncrashescombined.

• Publishedresearchsuggeststhatinitialstepstoaddressrightanglecrashesatsignal-controlledintersectionsinvolvecheckingclearance(YellowandAll-Red)intervalsandsignalhardware(overheadindications,12-inchlenses,andbackplatesprovidebettervisibilityfordrivers).

• AreviewofMinnesotacrashdataindicatesthattheuseof“good”clearanceintervalsandsignalhardwareisnotenoughtopreventrightanglecrashes.

• Intersectionswiththesefeatureshave(onaverage)ahigherdensityofseverecrashesthanintersectionswithonlypedestalmountedsignalswith8-inchlenses.

• Thisdatasuggeststhatadditionalenforcementeffortsarerequiredtoaddressdriverbehavior.AnAmericanAutomobileAssociationssurveyin2010foundthatmorethan30%ofrespondentsadmittedtorunningaredlightintheprevious30dayswhentheycouldhavesafelystopped.

Intersections – Red LightEnforcement


Highlights• DiscussionswithavarietyoflawenforcementofficershasfoundthatRLR

enforcementhasnotbeenapriority.Thisisprimarilyduetothefactthatittakestwoofficerstodoitsafely–oneontheapproachtoobservetheviolationandonepasttheintersectiontoissuetheticket–andmostagenciesdonothaveenoughofficerstodevotethislevelofeffortatasinglelocation.

• Nationally,thesolutiontolawenforcementstaffinglevelshasbeentheuseofredlightcameras.Studiesofeffectivenessofcamerashasdocumentedan80%reductioninallcrashes,a75%reductioninanglecrashes,anda60%reductioninRLR-relatedcrashes.Thestudiesalsofoundthatcamerasmayincreaserear-endcrashes,buttheytendtobelesssevere.1

• InMinnesota,redlightcamerasarenotallowedbystatelaw.Asaresult,anumberofagencies(CityofBurnsville,OlmsteadCounty,andMnDOT)haveimplementedanalternative,low-cost(typicallylessthan$2,000perinter-section)techniquetoassistlawenforcementeffortstoreduceRLR–theuseofconfirmationlights.

• Thesesmallbluelightsaremountedonthesideorthebackoftrafficsignalsupportsandarewiredinparallelwiththesignalsothatwhenthesignaldisplaysaredindication,theconfirmationlightilluminatesatthesametime.Theuseofconfirmationlightsallowsasingleofficerpasttheintersectiontobothobserveaviolationandsafelyapprehendtheviolator.

• Studiesofeffectivenessofconfirmationlightshavedocumentedcrashreductionsbetween30%and47%inFlorida.InMinnesota,theinstallationsaretoonewandtoofewtobeabletodocumentareductionincrashes.However,astudyoftwoinstallationsinBurnsvillefounda50%reductioninthenumberofviolations.2

1Toolbox of Countermeasures to Reduce Red Light Running,MidwestTransportationConsortium,InTrans10-386

2UnpublishedTechnicalmemorandumpreparedbySEH(ThomasSohrweide)andprovidedbytheCityofBurnsville

Intersections – Red LightEnforcement


Highlights• TheinstallationofstreetlightsisconsideredtobeaProven

effectivestrategyforreducingcrashes.

• Researchhasfoundthattheinstallationofstreetlightsatruralintersectionsreduced:

• Nightcrashesby26%to40%

• Nightcrashrateby25%to40%

• Nightsinglevehiclecrashesby29%to53%

• Nightmultiplevehiclecrashesby63%

• Nightcrashseverityby26%

• Abenefit/costanalysisfoundthatthecrashreductionbenefitsofstreetlightingatruralintersectionsoutweighcostsbyawidemargin.TheaverageB/Cratiowasabout15:1.

• Theresultsofrecentcasestudyresearchsuggeststhattheuseofstreetlightingismoreeffectiveatreducingnightcrashesthaneitherrumblestripsoroverheadflashers.

• AsurveyofpracticeamongMinnesotacountiesfoundtypicallightinginstallationcostsalongcountyfacilitiesintherangeof$1,000to$5,000perintersectionandannualoperationsmaintenancecostsintherangeof$100to$600perlight.

System-Wide Comparative Analysis

ItemIntersectionswithout

StreetLightsIntersectionswith

StreetLights ReductionStatistical

SignificanceIntersections 3236 259NightCrashes 34% 26% 26% YesNightCrashRate 0.63 0.47 25% YesNightSingleVehicleCrashes 23% 15% 34% YesNightSingleVehicleCrashRate 0.15 0.07 53% Yes

Before vs. After Crash Analysis

Item Before After ReductionStatistical

Significance

Intersections 12 12

NumberofNightCrashes 47 28 40% Yes

NightCrashes/Intersection/Year 1.31 0.78 40%

TotalCrashes/Intersection/Year 2.44 2.08 15%

NightCrashRate 6.06 3.61 40% Yes

TotalCrashRate 2.63 2.24 15% Yes

SeverityIndex 43% 32% 26% Yes

NightSingleVehicleCrashRate 4.0 2.84 29% Yes

NightMultipleVehicleCrashRate 2.06 0.77 63% Yes

Rural Intersections – Safety Effects of Street Lighting

MN/RC-1999-17


Highlights• AreviewofhistoriccrashdataindicatedthatSTOP-controlledruralintersec-

tionswithoverheadflashershadhigheraveragecrashratesthancomparableintersectionswithoutoverheadwarningflashers.

• AnecdotalinformationthatsurfacedduringtheinvestigationofseveralfatalcrashesindicatedthatsomedriversweremistakingYellow/RedwarningflashersforRed/RedflashersthatwouldindicateanAll-WaySTOPcondition.

• Inordertoaddresstheissueofeffectiveness,MnDOTcommissionedastudybytheUniversityofMinnesota’sHumanFactorsResearchLab1.Thestudyresultedinthefollowingconclusions:

• Aboutone-halfofdriverssurveyedunderstoodthewarningintendedbytheflasher,butmostdidnotadjusttheirbehavior.

• About45%ofthedriversmisunderstoodtheintendedmessageandthoughtitindicatedanAll-WaySTOPcondition.

• ThechangeincrashfrequencyatasampleofintersectionswasNOTstatisticallysignificant.

• Inresponsetothisresearch,MnDOThasbeenremovingoverheadflashers.

Warning Flashers at Rural Intersection, Minnesota Department of Transportation Final Report No. 1996-01. 1997

NEWOLD

Rural Intersections – Flashing Beacons

• Wherethereisevidencethatadditionalintersectionwarningisnecessary,optionsinclude–useofredflashersonSTOPsigns,advancewarningflashersonSTOPAHEADsigns,andflashingLEDsontheSTOPsign.Itshouldbenotedthatthefollow-upstudiesoneffectivenessoftheflashingLEDsfounda42%reductioninrightanglecrashesbutconcludedthattoofewcrashesmadetheresultsstatisti-callyunreliable.2

• Anotherstrategythathasbeenusedatruralintersectionsidentifiedasacandidateforsafetyinvestmentbasedoneitheranunusualfrequencyofseverecrashesorthroughasystemicriskassessmentinvolvestheuseofdynamicmain-linewarningsigns.AflasherontheadvancewarningsignisactivatedwhenthereisavehicleontheminorroadwaitingattheSTOPsigntoentertheintersection.Followupstudieshavedocumentedareductionincrashes,buttherehasnotyetbeenenoughinstallationsorstudiesofthedynamicwarningsystemtobeconsideredproveneffective.

Dynamic Mainline Warning Sign

2MnDOTLRRBReport2014-02,Estimating the Crash Reduction and Vehicle Dynamic Effects of Flashing LED Stop Signs,GaryDavis,UniversityofMinnesota

1MN/RC–1998/01,Warning Flashers at Rural Intersections, StirlingStackhouse,Ph.D.,UniversityofMinnesotaHumanFactorsResearchLaboratory


Highlights• Theuseoftransverserumblestripstoaddresssafetyissuesatruralintersectionshasbeenpartofthe

trafficengineer’stoolboxformanyyears.However,studiesonimplementationhavedemonstratedmixedresults.

• MnDOTtooktheopportunitytoperformathoroughstudyoftransverserumblestripsaspartofpreparingtheirdefenseinalawsuitallegingnegligenceonthestate’spartfornothavingrumblestripsataparticularintersection.Thestudyresultedinthefollowingconclusions:

• Theresultsofpreviousresearchdocumentedmixedresults,withsomestudiesshowingmodestimprovementandothersshowinganincreaseincrashes.Thelargeststudy,basicallystatewidealongsecondaryroads,showedanoverallincreaseincrashesattheintersectionswheretherumblestripswereinstalled.

• Abefore/afteranalysisof25ruralintersectionsinMinnesotafoundthattotalintersectioncrashesandrightanglecrashesactuallyincreasedafterinstallingrumblestrips.Thenumberoffatalplusinjurycrashesdeclinedslightly;however,noneofthechangeswerestatisticallysignificant.

• AprojectbytheUniversityofMinnesota’sHumanFactorsResearchLabfoundthatrumblestripshadaminoreffectondriverbehaviorrelativetospeedreductionandbreakingpatterns.However,therewasnoevidenceofcrashreduction.

• Formoreinformation,seeMnDOT’sTransportation Synthesis Report, TRS 0701 (www.lrrb.org/trs0701.pdf).

• StrategiesthathavebeenproveneffectiveatimprovingsafetyatruralThru/STOPintersectionsincludeenhancedsigns,markings(C-28),andstreetlights(C-35).

• Therelativeineffectivenessoftransverserumblestripsmaybeduetothefactthatthemajorityofcrashesatthru/STOPcontrolledintersectionsinvolvevehiclesthathavestoppedandthenproceedintotheintersection.Thesecrashesareattributedtogapselectionasopposedtointersectionrecognition.

• Ifaninvestigationofcrashesataruralintersectionindicatesmultiplerun-the-stopcrashes,theinstallationoftransverserumblestripscanbeconsidered.However,ifthereareanyhomesintheimmediatevicinityconsiderationshouldalsobegiventostrategiesthatwon’tgeneratenoisecomplaints.

MnDOT’s Transportation Synthesis Report, TRS 0701, August 2007

Rural Intersections – Transverse Rumble Strips

Number of Crashes (3-Year Period)

Before vs. After Change


Pedestrian Safety Strategies

Highlights• FatalcrashesinvolvingpedestriansareoneofAASHTO’sSafetyEmphasisAreas.In

theU.S.,thereareabout5,000pedestrianskilledeachyear,whichrepresentsabout11%ofalltrafficfatalities.

• Minnesotaaveragesabout37pedestrianfatalitiesannually(about9%oftotaltrafficfatalities).Theinvolvementrate(0.4pedestrianfatalitiesper100,000population)ranks47th–onlyRhodeIsland,NewHampshire,andIdahohavealowerrate.

• Nationally,fatalpedestriancrashesmostoftenoccurinurbanareas(67%),awayfromintersections(58%),andduringgoodweather(85%).Overtwo-thirdsofthepedestrianskilledaremale.

• Themostcommonpedestrianactivitiesassociatedwithfatalcrashesarewalking/workingintheroadandcrossingtheroadway.

• Contributingfactorsassociatedwithmotorvehicledriversincludefailuretoyieldrightofway(35%)anddriverinattention/distraction(21%).

• Tobetterassistagenciesinaddressingpedestrianandbicyclesafetyconcerns,MnDOTpreparedMinnesota’s Best Practices for Pedestrian/Bicycle Safety.Thedocumentidentifies19commonsafetystrategies,includingcrosswalkenhance-ments,newtechnologies,roaddiets,andspeedreductionmeasures.Adescriptionisprovidedforeachstrategy,alongwithanoverviewofsafetybenefits,typicalcharacteristicsofcandidatelocation,implementationcosts,andastatementofwhatconstitutesa“best”practice.

• AnotherresourcethatcanprovideassistanceindevelopingpedestriancrossingsisMnDOTReport2014-21:UncontrolledPedestrianCrossingEvaluationIncorpo-ratingHighwayCapacityManualUnsignalizedPedestrianCrossingAnalysisMeth-odology.Thisreportprovidesanoverviewofprevioussafetyresearchandpresentsamethodologyforestimatingthedelaythatapedestrianwouldexperiencewaitingforasafegapintrafficbasedonroadwaywidthandtrafficvolumes.Locationswithshortwaittimeswouldbeconsideredlow-prioritycandidatesforcrosswalkdevel-opmentandlocationswithlongwaittimeswouldbehigh-prioritycandidates.


Pedestrian Safety – Crash Rates vs. Crossing Features

Highlights• Threeofthemorecommonstrategiesintendedtoaddresspedestriancrashes

includereducingvehiclespeeds,providingamarkedcrosswalk,andinstallingatrafficsignal.

• Theresearchisabundantlyclear–merelychangingthepostedspeedlimithasneverreducedvehiclespeeds,paintingcrosswalksatunsignalizedintersectionsisactuallyassociatedwithhigherfrequenciesofpedestriancrashes,andinstallingatrafficsignalhasneverbeenproveneffectiveatreducingpedestriancrashes.

• Reducingvehiclespeedsisassociatedwithreducingtheseverityofapedestriancrash,butactuallyreducingspeedsrequireschangingdriverbehavior,whichrequireschangingtheroadwayenvironment.Strategiesthathavedemonstratedaneffectondriverbehaviorincludeverticalelements(speedbumpsandspeedtables),narrowingtheroadway(convertingfromaruraltoanurbansection),andextraordinarylevelsofenforcement.

• Across-sectionalstudyof2,000intersectionsin30citiesacrosstheU.S.foundthatmarkedcrosswalksatunsignalizedintersectionsareNOTsafetydevices.Thepedestriancrashratewashigheratthemarkedcrosswalksandthiseffectisgreatestformultilanearterialswithvolumesover15,000vehiclesperday.

• Abefore/afterstudyatover500intersectionsinSanDiegoandLosAngelesfounda70%reductioninpedestriancrashesfollowingtheremovalofmarkedcross-walksatuncontrolledintersections.

• Trafficsignalshavenotproventobeeffectiveatreducingpedestriancrashes–thehighestpedestriancrashfrequencylocationsinmosturbanareasaresignalizedintersections.

• Observationsofpedestrianbehaviorattrafficsignalssuggeststhatthereisalowlevelofunderstandingofthemeaningofthepedestrianindicationsandahighlevelofpedestrianviolations–veryfewpushthecallbuttonandfeweryetwaitforthewalkindication.

Charles V. Zegeer, et al., Safety Effects of Marked vs. Unmarked Crosswalks at Uncontrolled Locations: Executive Summary and Recommended Guide-lines, 1996-2001 (www.walkinginfo.org/pdf/r&d/crosswalk_021302.pdf)


Pedestrian Safety – Curb Extensions and Medians

Highlights• Pedestrianstrategiesthathaveproventobeeffective

includethefollowing:

• Overpass(inordertobeeffective,crossingtheroadwayat-grademustbephysicallyprevented)

• Street Lighting

• Refuge/Median Islands –Reducesvehiclespeedsatpedestriancrossinglocationsorintersections.

• Curb Extensions–Reducespotentialvehicleconflictsbyreducingpedestriancrossingdistanceandtime,andimproveslinesofsight.

• Sidewalks

• Road Diets(convertingfour-laneundividedroadstoathree-lanecross-section) –Eliminatesthemulti-vehiclethreatthatcanoccuronfour-laneroads.

Median Refuge Near Intersection Curb Extensions and Sidewalks

Road Diet (3 Lanes)

4-Lane Road


Highlights• Somemorerecentpedestrianandbicyclestrategies

include:

• Countdown Timers–Countdowntimersareflashingtimers,usuallyinstalledwithpedestrianindicationlights,whichprovidethenumberofsecondsremainingduringthepedestrianphase.

• Leading Pedestrian Interval –Aleadingpedestrianintervalprovidesthepedestrianwalk2or3secondsaheadofthevehiclegreen,allowingpedestriansaheadstartandtheabilitytoenterthecrosswalkbeforeright-turningvehiclescanturnintothecrosswalk.

• HAWK Signals–Shouldonlybeusedinconjunctionwithamarkedcrosswalkandtypicallynotatanintersection

• Bike Boulevards–stillconsideredexperimental–however,onestudylookingatsevenbikeboulevardsinBerkeley,founda60%reductioninbicycle-involvedcrashes.

Pedestrian/Bike Strategies


Complete Streets

Highlights• CompleteStreetsisatransportationnetworkapproach,involvingtheprovisionof

safeaccessforallstreetusers,thatmustbeconsideredduringtheplanninganddesignphasesofallroadwayimprovementprojects.CompleteStreetsisneitherproscriptivenoramandateforanimmediateretrofit;itishowever,intendedtobereflectiveoflocalneedsandtoserveadjacentlanduses.

• MnDOThasapolicythatrequirestheprinciplesofCompleteStreetstobeconsideredontrunkhighwaysatallphasesofplanningandprojectdevelopmentinordertoestablishacomprehensive,integrated,andconnectedmultimodaltransportationsystem.

• Agoodphrasetosummarizetheneedtodeterminetherightlocationstoimplementpedestrianandbicycleamenitiesisasfollows:“Notallmodesonallroads,rightmodeonrightroad.”

• MnDOT’sStateAidbicycleguidelineshavebeenmodifiedtoallowdesignersgreaterflexibilityinordertobeabletofitbicyclefacilitiesintoconstrainedcross-sectionsfoundalongexistingroadways.


Neighborhood Traffic Control Measures

Highlights • Neighborhoodtrafficcontrol(trafficcalming)usuallyinvolvesapplyingdesign

techniquesanddevicesonlocalstreetsinordertomodifydriverbehaviorandtrafficcharacteristics.

• Theapplicationofthesedevicesareusuallylimitedtoresidentialstreets,havebeeninfrequentlyusedonresidentialcollectors,andshouldnotbeconsideredonarterialsduetothepresenceoftransitvehicles,trucks,andemergencyresponders.

• Typicaltechniquesinvolvetheuseofsigns,markings,roadnarrowingordiverters,verticalelements,andtheuseoftechnologytoincreasetheenforcementpresence.

• Afewstudiesoftheeffectivenessofthesedeviceshavebeenconducted–thegeneralconclusionsare:

• Speedhumps/bumpsaremoderatelyeffectiveatloweringspeedsintherangeof3to7mphintheimmediatevicinityofthedevice.However,speedsbetweenthedeviceshavebeenobservedtoincrease.ItshouldalsobenotedthatthesedevicesareNOTallowedonanystate-aidedstreetorhighway.

• AddingSTOPsignslowersspeedsbyabout2mph,inthevicinityoftheSTOPsign,butalsoreducescompliance–agreaternumberofdriverscompletelydisregardthesignthancometoacompletestop.Inaddition,speedsinthesegmentsbetweenSTOPsignshavebeenobservedtoincreaseasdriversattempttomakeupforlosttime.OnefurtherpointshouldbeconsideredwhenevaluatingthepossibilityofaddingSTOPsignsforspeedmanagement-researchhasshownthatlowvolumeintersectionswithSTOPcontrolhaveahigherfrequencyofcrashesthanuncontrolledintersections.

• Changingspeedlimitsignshasneverchangeddriverbehavior.

• Enforcementdoeschangedriverbehavior-butthehaloeffectofenforcementmaybeassmallasafewminutes,soasustainedeffortisrequired.

www.ite.org/traffic/tcstate.asp

ITE, Traffic Calming - State of the Practice

ITE Traffic Calming Seminar


Highlights• TherearetwobasictypesofspeedzonesinMinnesota:

1. Statutoryspeedlimitsestablishedbythelegislature–30mphoncitystreets,55mphonruralroads,65mphonruralexpressways,and70mphonruralinterstates.

2. Speedzonesestablishedbasedontheresultsofanengineeringstudyofaparticularroadway.ThelegislaturehasassignedtheresponsibilityforsettingthespeedlimitsinthezonestotheCommissionerofTransportation.

• Thepremiseunderlyingtheestablishmentofspeedlimitsisthatmostdriverswillselectasafeandreasonablespeedbasedontheirperceptionoftheroadway’sconditionandenvironment.Thishasledtothepracticeofconductingastatis-ticalanalysisofasampleofactualvehiclespeedsaspartofacomprehensiveengineeringinvestigation.

• Thetwoprimaryperformancemeasuresare:

1. 85thpercentilespeed–Thespeedbelowwhich85%ofthevehiclesaretraveling.

2.10mphpace–the10mphrangethatcontainsthegreatestnumberofvehicles.

• Experiencehasshownthatthemosteffectivespeedlimitsarethosethatareclosetothe85thpercentilespeedandintheupperpartofthe10mphpace.

• Thegraphatthetopofthispageillustratestherelationshipbetweenvehiclespeedsandcrashrates.Thedataindicatesthatwherevehiclespeedsareintherangeof5to10milesperhourabovetheaveragespeed(whichapproximatesthe85thpercentilespeedinmostspeedprofiles)crashratesarethelowest.

• ThegraphatthebottomofthispageillustratestherelationshipbetweenspeedlimitandaveragecrashratesforurbanhighwaysontheState’ssystem.ThisdataindicatesthatinMinnesotacrashratesgodownasspeedlimitsincreasealongurbanhighways.

• ItshouldbenotedthatasimilarrelationshipbetweenspeedlimitsandcrashesisdocumentedintheHSM.ThesameMinnesotaresearchindicatesthataccessdensityisabetterpredictorofurbancrashratethanisthepostedspeedlimit.

“Statistical relationship between vehicular crashes and highway access” Report: MN/RC–1998–27

Speed Zoning


Highlights• InMinnesota,statestatutesassigntheestablishmentofspedzonesto

theCommissionerofTransportationinordertoachieveaconsistencyacrossallroadsinMinnesota.

• Speedzonesareestablishedbasedonananalysisofexistingvehiclespeedsalongasegmentofroadwayandavarietyofotherinformationincludingroadcross-section,densityofaccess,landuseandothercharacteristicsoftheroadenvironment.

• Inanumberofcases,localauthoritieshavequestionedtheoutcomesofthetechnicalanalysisandrequestedthepostingofalowerspeedlimit.Thetabletotheleftillustratestheoutcomeofexperimentsthatwereconducted–thepostedlimitswerechangedandlocalagen-cieswereinvitedtoapplyasmuchenforcementasstafflevelswouldallow.Theoutcomewasidenticalinallcases,driverbehaviordidnotchange.

• Theseexperimentssupportthenotionthatamajorityofdiverspickasafeandcomfortablespeedbasedontheirperceptionoftheroadenvironmentandonlychangingthepostedspeeddidnotchangetheirbehavior.

Speed Zoning Studies

Study Location Before After

Sign Change +/- MPH

85% Before After

Change MPH

TH 65SPEEDLIMIT40

SPEEDLIMIT30 -10 34

34 0

TH 65SPEEDLIMIT50

SPEEDLIMIT40 -10 44

45 +1

Anoka CSAH 1

SPEEDLIMIT45

SPEEDLIMIT40 -5 48

50 +2

Anoka CSAH 24

SPEEDLIMIT30

SPEEDLIMIT45 +15 49

50 +1

Anoka CSAH 51

SPEEDLIMIT40

SPEEDLIMIT45 +5 45

46 +1

Hennepin CSAH 4

SPEEDLIMIT50

SPEEDLIMIT40 -10 52

51 -1

Noble AveSPEEDLIMIT30

SPEED�LIMIT35

SPEED�LIMIT35

SPEEDLIMIT35 +5 37

40 +3

62nd Ave NSPEED�LIMIT35

SPEED�LIMIT35

SPEEDLIMIT35

SPEEDLIMIT30 -5 37

37 0

Miss. StSPEEDLIMIT30

SPEED�LIMIT35

SPEED�LIMIT35

SPEEDLIMIT35 +5 39

40 +1

Minnesota Department of Transportation (MnDOT)

Speed Zoning


Speed Reduction Efforts

Highlights• Beyondmerelychangingthepostedspeedlimit,

effortstochangedriverbehaviorhavefocusedontwoapproaches–addedenforcement(remember–electronicenforcementisnotallowedinMinnesota)andmakingchangestotheroadenvironmentinordertoadjustdriverperception.

• Theuseofaddedenforcement(besuretocheckwithyourlocalpolice/sherifftodetermineiftheyhavetheresourcestoprovideahigherlevelofenforce-ment)producesahighlevelofconsistencywiththepostedlimitBUTonlywhentheofficersarepresent.Thespillover(“Halo”)effectofenforcementhasbeenobservedtobeaslittleasafewminutesandrarelyaslongasaweek.

• Oneapproachtochangingdriverperceptionofspeedinvolvesaddingpavementmarkings(toprovideanillusionofspeed),reinforcingpavementmessages,verticalelementsanddynamicsigning.Theresultsoftheseattempts(seetable)haveproven,inmostcases,tobeverylimited.

• Asecondapproachtochangingdriverperceptioninvolvesreconstructingtheroadwaytoadddesignelementsthatreinforcethenotionofanurbanenvironmentandlowerspeedsthataretypicalintheseareas.Atypicaloperatingspeedonatwo-lanesuburbanroadisinthe40to45mphrangebutonasimilartwo-laneurbanroadwithcurb,gutter,andsidewalk,thetypicaloperatingspeeddropstoaround30mph.

Summary of Impacts and Costs of Rural Traffic Calming Treatments

Treatment

Change in 85th Percentile Speed (mph) Cost Maintenance Application

Transversepavementmarkings(1) -2to0 $ Regularpainting Communityentrance

Transversepavementmarkings(1)withspeedfeedbacksigns -7to-3 $$$ Regularpainting Community

entrance

Lanenarrowingusingpaintedcenterislandandedgemarking -3to+4 $ Regularpainting Entranceorwithin

community

Convergingchevrons(1)and“25MPH”pavementmarkings -4to0 $ Regularpainting Community

entrance

Lanenarrowingusingshouldermark-ingsand“25MPH”pavementlegend -2to4 $ Regularpainting Entranceorwithin

community

Speedtable -5to-4 $$ Regularpainting Withincommunity

Lanenarrowingwithcenterislandusingtubularmarkers -3to0 $$$ Tubesoftenstruck

needingreplacementWithincommunity

Speedfeedbacksign(3monthsafteronly) -7 $$$ Troubleshooting

electronicsEntranceorwithincommunity

“SLOW”pavementlegend -2to3 $ Regularpainting Entranceorwithincommunity

“35MPH”pavementlegendwithredbackground(1) -9to0 $

Backgroundfadedquickly;acceleratedrepaintingcycle

Entranceorwithincommunity

Traffic Calming on Main Roads Through Rural Communities, FHWA-HRT-08-067, Krammes, R., 2009

(1)ExperimentalapprovalrequiredperSection1A.10ofMUTCD.

$ =under$2,500$$ =$2,500to$5,000$$$=$5,000to$12,000

Designing Roads That Guide Drivers to Choose Safety Speeds, Iran, J. & Garrick, N., Connecticut Transportation Institute, 2009


Highlights• In1975theLegislaturechangedMinnesotaStatute169.14

toallowlocalauthoritiestoestablishspeedlimitsinschoolzones.Keyprovisionsofthelawinclude:(A)Localauthoritiesmayestablishaschoolspeedzonebasedontheoutcomeofanengineeringandtrafficinvestigation,(B)Schoolspeedlimitsmaynotbelowerthan15milesperhourormorethan30milesperhourbelowtheestablishedspeedlimitand(C)Theschoolspeedzoneisdefinedasthatsectionofstreetorhighwaythatabutsschoolpropertyorwherethereisanestablishedschoolcrossingwithadvancedschoolsignsthatdefinethearea.

• EstablishingaschoolspeedzoneonastatetrunkhighwayrequirestheapprovaloftheCommissionerofTransportation.

• Thesignsthatareusedtoconveythemessagetodriversthattheyareapproachingaschoolareaandschoolspeedzoneinclude:

• AdvanceSchoolsign

• SchoolZoneSpeedLimitsign

• Avarietyofalternativeplaquesthatdescribewhentheschoolspeedlimitisineffect–timesoftheday,WHENCHILDRENAREPRESENT,orWHEN(anattachedflasheris)FLASHING.

• Localauthoritiesestablishingaschoolspeedzoneshouldbeawarethatsimplypostingthesignsdesignatingaschoolspeedzonedoesnotguaranteethateitheramajorityofdriverswillactuallylowertheirspeedorthatchildrenwillbesafer.Researchconfirmsthatmostdriverspickaspeedthattheyperceiveissafebasedontheirassessmentofthedrivingenvironment.Asaresult,simplyaddingasignestablishingalowerspeedlimitmayhaveonlyamarginaleffectonactualvehiclespeeds.

Speed Zoning – School Zones

• WashingtonCountyhasconductedaninvestigationoftheeffectsonvehiclespeedsassociatedwithdesignatingaschoolspeedzonewithflashinglightsalongaruralroad-ways.Theresultsindicatevehiclespeedsdroppedbyfivemilesperhourandthenumberofvehiclesinthepacedroppedbymorethan20%.

• Thepresenceofschoolchildrenduringtheschoolarrivalanddepartureisanobviouschangeinthedrivingenviron-mentandithasbeenobservedthatdriverswilllowertheirspeedswhenchildrenarepresent.However,iftheschoolisnotimmediatelyadjacenttotheroadwayorifthechildrendonotwalktoschool,theremaybenochildrenvisibletodrivers.Ineithercase,techniquesforimprovingdrivercomplianceinclude:

• Makingthesignsdynamicwithflashersthatoperateonlyondayswhenschoolisinsessionandhourswhenchildrenarelikelytobepresent.

• Partneringwithlocallawenforcementtooccasionallyprovideavisiblepresence.

• Afinalpointaboutschoolspeedlimits–thesafetyofchildrenwillbeoptimizediftheestablishmentofaschoolspeedlimitispartofacomprehensiveprogramthatalsoincludesconsiderationoftheroadgeometry(mediansandcurbextensionshavebeenproveneffectiveatimprovingpedestriansafety),theuseofadultcrossingguards,theavailabilityofasidewalksystem(alsoproveneffectiveatimprovingpedestriansafety),andstrategicfencingoftheschoolproperty.

Minnesota Manual on Uniform Traffic Control Devices, January 2014

School Zone Signage Placement

School Speed Limit Signage


Highlights• Nationalresearchsuggeststhatthemosteffectivespeedmanagementstrategy,Automated

SpeedEnforcement,resultsinbothlowerspeedsandfewercrashes.Crashreductionsintherangeof15to50%havebeendocumented.AutomatedSpeedEnforcementiscurrentlyusedin14statesbutnotMinnesota,eventhoughpublicopinionpollsshowsupport.

• AccordingtoNHTSA,acrashonaroadwithaspeedlimitof65mphorgreaterismorethantwiceaslikelytoresultinafatalitythanacrashonaroadwithaspeedlimitof45or50mphandnearlyfivetimesaslikelyasacrashonaroadwithaspeedlimitof40mphorbelow.

• CongressrepealedtheNationalMaximumSpeedLimitoninterstatehighwaysin1995.In2014,fourstateshaveraisedpostedlimitstoashighas80mphorextendedmaximumlimitstomoreroads.Inall,38stateshavespeedlimitsof70mphorhigheronsomeportionoftheirroads,despiteresearchshowingthatanincreaseintrafficdeathswasattributabletoraisedspeedlimitsonallroadtypes(www.iihs.org/iihs/sr/statusreport/article/49/6/3).

• Strategiesthathavebeenusedtoaddressspeedinginclude:

• Stepped-uphigh-visibilityspeedenforcement(HVE)suchasMinnesota’sStatewideSpeedEnforcementDayandspeedcampaigninvolvingenforcementagenciesacrossthestatefocusingonspeedviolationsinthesummermonths,thedeadliesttimeonMinne-sotaroads.HVEhasdemonstratedanabilitytoreducethenumberofdriversexceedingthespeedlimitbymorethan10milesperhourbyapproximately30%.However,itwasalsodeterminedthattheeffectofthistypeofsaturationenforcementdiminishedovertime(the“HaloEffect”).ObservedcrashreductionsassociatedwithHVEareintherangeof3%to5%ofallcrashesduringtheevent.

• Publicinformationandeducationprogramsthatpublicizeupcomingenforcementpro-gramsandeducatethepubliconthedangersofspeedandaggressivedriving.

• Increaseemphasisonemployerpoliciesrelatedtodrivingatlegalandsafespeeds.

Speed Strategies

2013 Minnesota Speeding Fact Sheet, Minnesota Department of Public Safety, Office of Traffic Safety, 2014


Survey of the States: Speeding and Aggressive Driving, 2012, GHSA

Countermeasures That Work: A Highway Safety Countermeasure Guide for State Highway Safety Offices, 2013, NHTSA


Technology Applications

Highlights• TheFHWAandMnDOThaveinvestedinaconsiderableamountofresearchregardingtheuseofnew

technologytoaddresstrafficoperationsandsafetydeficiencies.

• Advancedtechnologieshavebeensuccessfullydeployedtoaddressfreewaytrafficmanagement,andanewgenerationoftrafficsignalcontrollersandopticaldetectorsareimprovingtrafficflowonurbanarterials.

• Researchiscurrentlyunderwayatseveraluniversities,includingtheUniversityofMinnesota,LRRBtobetterunderstandfactorscontributingtointersectioncrashesinordertodevelopnewdevicesforassistingdriversinselectingsafegapsatuncontrolledintersections,makingsaferturnsatcontrolledintersections,andprovidingadditionalwarningwhendriversviolatetheintersectioncontrol.

• InresponsetoanoverrepresentationofseverecrashesatruralThru/STOPintersections,MnDOTandtheUniversityofMinnesota–Duluthdevelopedandfield-testedanewdynamicwarningsystem–theAdvancedLEDWarningSystemforRuralIntersections(ALERT)1.Thesystemutilizesfourbasictechnologies:

• LEDsigns

• Renewableenergy

• Non-intrusivesensors

• Wirelesscommunication

• Thesystemdetectsthepresenceofvehiclesapproachingtheintersectiononboththemajor(Thru)andminor(STOP)approachesthatactivatesflashinglightsonaseriesofWarningsignsandtheSTOPsign.

• Anevaluationofthesystem’sperformancefoundthatvehiclespeedsonthemajorapproachwerereducedandthenumberofvehiclesthatrolledthroughtheSTOPsignwaseliminatedwhenaconflictexistedintheintersection.

• Theevaluationdidnotconsidercrashesbecausethereweretoofewcrashesatthesingleintersectionselectedforthefieldoperationaltesttobeconsideredstatisticallyreliable.

1MnDOTReportNo.2014-10,Advanced LED Warning System for Rural Intersections: Phase 2 (ALERT-2)


Highlights• ThelegallimitfordrivingwhileimpairedinMinnesotais0.08–butmotoristscanbearrestedforDWIatlowerlevels.

Abloodalcoholconcentration(BAC)of0.08oraboveisacriminaloffenseand,inMinnesota,isaviolationofcivillawthattriggersautomaticdriverlicenserevocationforuptoayear.

• OfalloffendersinMinnesota,thevastmajority–nearly60%–arefirst-timeoffenders;nearly40%ofoffendersarerepeatoffenderswithoneormoreDWIsonrecord.OneoutofeverysevenlicenseddriversinMinnesotahasatleastoneDWI.

• Strategiesthatareproveneffectiveatdecreasingimpaireddrivinginclude:

• High-visibilityimpaired-drivingenforcementsuchasthenationwideDriveSoberorGetPulledOverdrunkdrivingcrackdownscombininghighvisibilitylawenforcementandpublicawarenesstodeterordetectdrunkdrivers.Researchshowsthathigh-visibilityenforcementcanreducedrunkdrivingfatalitiesbyasmuchas20%.

• Nighttimebeltenforcement.(Note:Eachyear,nearly70%ofdrinkingdriverskilledincrashesarenotbuckledup).

• AlcoholignitioninterlockstoseparatedrinkingdriversfromtheirvehicleandreducerepeatDWIoffenders.

− Ignitioninterlockshavebeenshowntoreducere-arrestbyarangeof50%to90%.

− InMinnesota,allrepeatDWIoffenders–andfirst-timeoffendersarrestedattwicethelegallimit–mustusealcoholignitioninterlocksorfaceatleast1yearwithoutadriver’slicense.

− In2012,therewere28,418impaired-drivingincidentsinMinnesotaand4,050interlockswereinuse.

− Bycomparison,sevenstateshavemorethan20,000interlocksinuse,ledbyTexas(38,000),andthreestatesdonotuseinterlocks(NorthDakota,MississippiandAlabama).

− Twostateshaveaninterlock-in-usetoDWIratiogreaterthan1.0–Washington(2.5)andNewMexico(1.1).Minnesota’sratiois0.2.

• Administrativelicenserevocation/suspension(immediatelicenserevocation/suspensionuponfailureorrefusalofaBACtest).

• DWIanddrugcourtstocloselymonitoroffendersandtheirtreatment.

• ScreeningandbriefinterventiontechniquesbythecourtsforDWIoffenders.

• TechnicalassistanceandsupporttothosewhoprosecuteDWIoffenses.

Impaired Driver Strategies

2013 Minnesota Impaired Driving Fact Sheet, Minnesota Department of Public Safety, Office of Traffic Safety, 2014


2012 Impaired Driving Crash Facts, Minnesota Department of Public Safety, Office of Traffic Safety, 2013

Countermeasures That Work: A Highway Safety Countermeasure Guide for State Highway Safety Offices, NHTSA, 2013

Ignition Interlocks – What You Need to Know, DOT HS 811 883, NTSA, 2014

NHTSA: www.trafficsafetymarketing.gov/laborday2014peak


Highlights• Inattentionhasbeenfoundtocontributetoapproximately19%ofseverecrashesandMinnesotalawenforcement

expectsdriverinattentionordistractionasbeingsignificantlyunderreported.

• Strategiestoreducedistracteddrivinginclude:

• Stepped-up high-visibility enforcement (HVE)ofdistracteddrivinglaws,includingroutinetrafficpatrolsthatincludedistracteddrivingenforcementtotargetedeffortsfocusedonspecificeventssuchasthenationalannualDistractedDrivingAwarenessMonthcampaign.

• Focusing on high-risk young drivers and using social mediasuchasTwitter,YouTube,andFacebook,inadditiontotraditionalmedia,tomoreeffectivelycommunicatethesafetyrisksandchangingsocialnormsassociatedwithsmartphones,aswellasotherdistractions.

• Strengthening public/private partnershipstoreinforcesafedrivingpractices.Minnesota,similartoCalifornia,Nebraska,andTexas,isworkingwithitsstateaffiliateoftheNationalSafetyCounciltoprovideanddevelopedu-cationanddistracteddrivingpoliciestomajoremployers–theMinnesotaTowardsZeroDeathProgram.

• Improving crash data collectiontomoreaccuratelydeterminethemagnitudeandimpactofdistracteddrivingandtosupportthedevelopmentofsafetysolutions.

• Challengestoreducingandenforcingdistracteddrivinginclude:

• Themotoringpublic’sunwillingnesstoputdowntheirphones,despiterecognizingthedangersofdistracteddriving.

• Enforcementofficers’abilitytodiscernwhetheramotorististextingordialingaphone,asthelatterispermittedinMinnesotaandinmoststates.

• Distracteddrivingisunder-reportedduetodriverreluctancetoadmitbeingdistracted.

• Thelackoffundingforenforcement,media,andpubliceducation.

Inattention Strategies

Distracted Driving: Survey of the States, 2013, GHSA

2013 Inattentive Driving Facts, Minnesota Office of Traffic Safety



Distracted Driving High-Visibility Enforcement Demonstrations in California and Delaware, 2014, DOT HS 811 993

Four High Visibility Enforcement Waves in Connecticut and New York Reduce Hand-Held Phone Use, 2011, DOT HS 811 845.


Highlights• Minnesota’sseatbeltlawisaprimaryoffense,meaningdriversandpassengersinallseating

positionsmustbebuckleduporinthecorrectchildrestraintorlawenforcementwillstopandticketunbelteddriversorpassengers–includingthoseinthebackseats.

• Minnesotaoccupantrestraintusagerateis95%(June,2013)–thehighestinMinnesotahistory.Nationally,seatbeltuseismuchlower(86%in2012).

• Properlywearingaseatbeltreducestheriskoffatalinjurytofront-seatpassengersby45%inacarand60%inalighttruck.Seatbeltsarethemosteffectivemeansofprotectingoneselffrominjuryintheeventofacrash.

• Inacrash,oddsaresixtimesgreaterforinjuryifamotoristisnotbuckledup.

• Minnesotansthatareleastlikelytobuckleupandmorelikelytodieincrashesareyoungervehicleoccupantsages15to29,whoannuallyaccountfornearly43%ofallunbelteddeathsandnearly50%ofallunbeltedseriousinjuries–yetthisgrouprepresentsonly23%ofalllicenseddrivers.

• Strategiesthatareproveneffectiveatincreasingoccupantseatbeltuseinclude:

• High-visibilityseatbeltenforcement(incorporatesmediaandpublicoutreachabouttheenforcement)

• Nighttimebeltenforcement

• Focusedenforcementandsupportingoutreachtohigh-risk,low-belt-usegroups.

Unbelted Strategies

2013 Seat Belt Overview, Minnesota Office of Traffic Safety


Occupant Protection 2012 Traffic Safety Facts, 2014, NHTSA



Temporary Traffic Control Zones

Highlights • AddressingcrashesintemporarytrafficcontrolzonesisoneofAASHTO’ssafetyfocus

areas.Therewere87,600crashesintemporarytrafficcontrolzonesin2010thatresultedin576fatalitiesand37,476injuries.

• Minnesotaaveragesaround1,900crashesintemporarytrafficcontrolzones,withapproximately20resultingineitherafatalityorseriousinjury.

• CrashesintemporarytrafficcontrolzonesareidentifiedasasafetyfocusareainMinnesota’sStrategicHighwaySafetyPlan.

• Temporarytrafficcontrolzonescanbeachallengefordriversbecauseofavarietyofunexpectedconditions–distractions,congestion,andagreaterdemandformoreprecisenavigation.

• AreviewofMinnesota’stemporarytrafficcontrolzonecrashesfoundthatthemostfrequenttypeisarear-endcrash,andcommoncontributingfactorsincludeinattention(30%)andspeeding(26%).

• Providinganeffectivespeedlimitintemporarytrafficcontrolzonesisextremelyimportant,butitmustbenotedthatsigningalonewillnotreducevehiclespeeds.Driversmustclearlyperceivetheneedtoreducespeedbasedontheirreactiontothedesignoftheapproachandtheplacementoftrafficcontrolandchannelizingdevices.Considerationshouldalsobegiventohavinganenforcementpresencetofurtherencouragedriverstoslowdown.


Highlights • Therearethreemethodsofspeedlimitsigningfortemporarytrafficcontrolzones:

AdvisorySpeeds,24/7ConstructionSpeedLimits,andWorkersPresentSpeedLimits.

• Advisory Speeds:AdvisoryspeedplaquescombinedwithWarningsignsnotifydriversofpotentiallyhazardousconditions,suchasbypasses,laneshifts,lowandnoshoulders,andwherevisibilitymaybereducedduetoworkactivities.TheuseofadvisoryspeedplaquesdoesNOTrequireauthorizationfromtheCommissionerofTransportation

• 24/7 Construction Speed Limit:Regulatoryspeedlimitsthatremaininplaceona24-hourbasisandrequireanorderfromtheCommissionerofTransportation.Thesespeedlimitsareusedwherethephysicalfeaturesoftheroadrequirelowervehiclespeeds,suchasbypassesoratwo-lane/two-wayoperationonwhatisnormallyafour-lanedividedhighway.

• Workers Present Speed Limit:Regulatoryspeedlimit,butdoesNOTrequireauthorizationfromtheCommissionerofTransportation.MinnesotaStatute169.14.5d.(c)allowslocalroadagenciestosetatemporarytrafficcontrolzonespeedlimitwhenworkersarepresentandworkingdirectlyadjacenttotravellanes.

• Minnesotasetsafineof$300forviolationofaregulatoryspeedlimitinatemporarytrafficcontrolzone.Asaresult,anENDWORKZONESPEEDLIMITorENDROADWORKsignmustbeusedtoindicatetheendofthehigher-finearea.

• MnDOTresearchsupportsthenotionthatsigningalonewillnotreducevehiclespeeds.Inadditiontousingthedesignoftheapproachtothetemporarytrafficcontrolzoneandtheplacementofchannelizingdevicestoconveyamessagetoslowdown,twootherstrategieshavebeenshowntoachievespeedreductions:thepresenceoflawenforce-mentandtheuseofdynamicspeedfeedbacksigns.

Temporary Traffic Control Zones

A“WhenWorkersPresent”speedlimitof45mphisrequiredwhen:

1.Atleastaportionofentirelaneisclosed

2.Workersarepresent

Itisnotrequiredif,

1. Positivebarriersareplacedbetweenworkersandtraveledlanes

2.Workzoneisinplaceforlessthan24hours

3.A24/7speedlimitisestablished

4.Areducedspeedlimitisauthorizedbytheroadauthoritywhenworkersarepresent

Minnesota Manual on Uniform Traffic Control Devices, January 2014


Average Crash Costs

Highlights• MnDOTusesthefollowingcomprehensive

crashcostswhencomputingtheexpectedben-efitsassociatedwithroadwayandtrafficcontrolimprovements.

• Thecostsshownweredevelopedin2013byMnDOTonapercrashbasisforuseincalculatingbenefit/costcomparisonsonly.Thecostsincludeeco-nomiccostfactorsandameasureofthevalueoflostqualityoflifethatsocietyiswillingtopaytopreventdeathsandinjuriesassociatedwithmotorvehiclecrashes.CostsreflectMinnesota’s3-yearcrashhistoryandtheUSDOTprocedurescontainedinRevised Department Guidance 2013: Treatment of the Value of Preventing Fatalities and Injuries in Preparing Economic Analyses.

• Duetotheveryhighcostforfatalcrashesandtheeffectthiscanhaveontheoutcomeofbenefit/costanalyses,itisthepracticeinMinnesotatovaluefatalcrashesas2x”SeverityACrash”($1,100,000percrash)unlessthereisahighfrequencyoffatalcrashesofatypesusceptibletocorrectionbytheproposedaction.

$

$

$

$

$

10,300,000 Per FATAL Crash

550,000 Per SEVERITY A Crash

160,000 Per SEVERITY B Crash

81,000 Per SEVERITY C Crash

7,400 Per PROPERTY DAMAGE ONLY Crash

Developed by MnDOT Office of Traffic, Safety and Technology

Incapacitating Injury

Non-incapacitating Injury

Possible Injury


Crash Reduction Benefit/Cost(B/C) Ratio Worksheet

Highlights• Comparingtheexpectedcrashreductionbenefitsofapar-

ticularsafetycountermeasuretotheestimatedcostofimple-mentationisanacceptedanalyticaltoolusedinevaluatingalternativesatonelocationortoaidintheprioritizationofprojectsacrossasystem.

• Thebasicconceptistogivepreferencetotheproject(s)thatproducedthegreatestbenefitfortheleastamountofinvest-ment.

• Theworksheetcalculatesbenefitsastheexpectedreductionincrashcostsonanannualbasisandcomparesthisvaluetotheannualizedvalueoftheestimatedconstructioncost.

• Themethodologyonlyaccountsforbenefitsassociatedwithcrashreduction.However,theprocesscouldberevisedtoalsoaccountforotherbenefits,suchasimprovedtrafficoperations(reduceddelayandtraveltimes).

• Itshouldbenotedthatbenefit/costanalysisdoesnotattempttoaccountforallpotentialbenefitsassociatedwithanyparticularproject,sincesomeeconomicandsocialbenefitsareverydifficulttoquantify.

• Substantialresearchisdedicatedtodevelopingcrashmodi-ficationfactors(CMFs)toquantifytheimpactofvarioussafetystrategies.Nationwide,CMFstudiesarestoredattheCMFClearinghouse(www.cmfclearinghouse.org)andshouldbeusedtoestimatetheimpactsofvarioussafetystrategieswhenconductingabenefit-coststudy.

Note:TheExcel™spreadsheetfilemaybedownloadedfromMnDOT’sWebsite


Typical Benefit/Cost Ratios for Various Improvements

Highlights• TheFHWAhasdocumentedthebenefit/costratios

foravarietyoftypicalsafety-relatedroadwayimprovements.

• Typicalbenefits/costsrangedfrom1.9forskidoverlaysto21.0forillumination.

• Thesebenefits/costsshouldonlybeusedasaguideandnotasthedefinitiveexpectedvalueatanyparticularlocationinMinnesota.

• Benefits/costsintherangeof2to21wouldlikelyonlybeachievedatlocationswithcrashfrequenciessignificantlyhigherthantheexpectedvalues.

• MnDOT-fundedsafetyresearchhasdocumentedbenefits/costsforavarietyofsafetyprojects,including:

• Streetlightingatruralintersections(21:1)

• Cablemedianbarrieralongfreeways(10:1)

• Accessmanagement(intherangeof3:1to1:1)

Rank Construction Classification B/C Ratio1 Illumination 21.0

2 RelocatedBreakawayUtilityPoles 17.2

3 TrafficSigns 16.3

4 UpgradeMedianBarrier 13.7

5 NewTrafficSignals 8.3

6 NewMedianBarrier 8.3

7 RemoveObstacles 8.3

8 ImpactAttenuators 7.8

9 UpgradeGuardrail 7.6

10 UpgradedTrafficSignals 7.4

11 UpgradedBridgeRail 7.1

12 SightDistanceImprovements 7.0

13 GroovePavementforSkidResistance 5.6

14 ReplaceorImproveMinorStructure 5.2

15 TurningLanesandTrafficSeparation 4.4

16 NewRailRoadCrossingGates 3.9

17 ConstructMedianforTrafficSeparation 3.3

18 NewRailRoadCrossingFlashingLights 3.2

19 NewRailRoadFlashingLightsandGates 3.0

20 UpgradeRailRoadFlashingLights 2.9

21 PavementMarkingandDelineations 2.6

22 FlattenSideSlopes 2.5

23 NewBridge 2.2

24 WidenorImproveShoulder 2.1

25 WidenorModifyBridge 2.0

26 RealignRoadway 2.0

27 OverlayforSkidTreatment 1.9

FHW

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D-1

Lessons LearnedSection D


D-2 Crash Characteristics

D-3 Safety Improvement Process

D-4 Traffic Safety Tool Box

D-2

Lesson Learned – Crash Characteristics

Highlights• AttheNationallevelthenumberoftraffic-relatedfatalitiesduringthepast10

yearshasdroppeddramaticallyfromalmost43,000deathstojustunder33,000.

• Overthissame10-yearperiod,thetrendinMinnesotaissimilar–thenumberoftraffic-relatedfatalitieshasdeclinedfromover650trafficfatalitiestofewerthan400peryear.

• In2013thenationalfatalityratewas1.1fatalitiesper100millionvehiclemilestraveledandtherangewas0.6to1.9.Minnesota’sfatalcrashratewas0.7–thesecondlowestinthecountryandthelowestofanystatenotinthenortheast.

• FatalcrashesinMinnesotaarenotdistributedevenlyacrossthestate–66%offatalitiesareinruralareasandthefatalityrateonruralroadsisnearly3timestherateinurbanareas.

• Thenationalsafetyperformancemeasureisthenumberofsevereinjuries–fatalitiesplusincapacitatinginjuries.

• Factorsthatcontributetoseverecrashesinvolvedrivers,theroadwayandvehicles.Driverbehaviorisafactorinmorethan90%ofcrashes,roadwayfeaturesareafactorinslightlymorethanone-thirdofcrashesandvehiclefailuresareafactorinaround10%ofcrashes.

• Theadoptionofthenewsafetyperformancemeasurewithafocusonseverecrasheshasresultedinabetterunderstandingofthefactthatfatalcrashesaredifferentthanlessseverecrashes.Themostcommontypeofcrashisarear-end(31%ofallcrashes);however,themostcommontypesoffatalcrashesincluderun-off-road(32%),anglecrashes(21%)andhead-oncrashes(20%).

• Crashesarenotevenlydistributedacrossthepopulationofdrivers–youngdrivers(underage21)representabout6%ofalldriversbutareinvolvedinalmost11%ofcrashes.


• Mostcrashesoccurondryroadsingoodweatherandduringdaylightconditions–it’safunctionofexposure.However,nighttimehourspresentagreaterriskforseverecrashes–25%ofallcrashesoccurduringdarkconditionsbut31%offatalcrashesoccurduringthehoursofdarkness.

• Contrarytopopularopinion,signalizedintersectionsarerarelysafetydevices.Theaveragecrashrate,severityrate,andcrashdensityishigheratsignalizedintersectionscomparedtothestatisticsforSTOP-controlledlocations.

• Themostcommontypesofintersection-relatedcrashesarerear-endandrightangle.Theinstallationofatrafficsignalchangesthecrashtypedistribution–increasingrear-endandleftturncrashes.However,thefractionofrightanglecrashesremainsvirtuallyunchanged–thereisasubstantialandwidespreadprobleminvolvingred-lightrunning.

• Crashratesonroadwaysegmentsareafunctionoflocation(ruralvs.urban),design(conventionalvs.expresswayvs.freeway)andthedegreetowhichaccessismanaged.Ruralfreewaysandtwo-laneroadshavethelowestcrashrates,urbanminorarterialshavethehighestcrashrates,andruralcountyhighwaysandtown-shiproadshavethehighestfatalcrashrates.

• Urbancrashesarepredominantlytwovehicle(rear-endandrightangle)andruralcrashesarepredominantlysinglevehicle(run-off-roadanddeerhits).

• Withindesigncategoriesofroads(ruraltwo-lane,urbanfour-lane,expressway,etc.)thedensityofaccesscanbeusedtopredictcrashrates–segmentswithhigheraccessdensitieshavehighercrashratesinbothruralandurbanareas.

• Severeinjurycrashesinvolvingpedestriansandbicyclistsaccountforapproxi-mately14%ofallseverecrashesinMinnesota.Nearlytwo-thirdsofthesecrashesoccurintheMinneapolis-St.PaulMetropolitanAreaandthemajorityoftheseoccuronstreetswitha30MPHspeedlimitandatintersectionscontrolledbytrafficsignals.

D-3Traffic Safety Fundamentals Handbook – 2015

Lesson Learned – Safety Improvement Process

Highlights• MnDOT’sStrategicHighwaySafetyPlan(SHSP)isadata-drivendocumentthat

adoptsseverecrashesasthesafetyperformancemeasure(fatalandincapacitatinginjurycrashes).TheSHSPalsoadoptsashort-termsafetygoal–300orfewerfatalitiesby2020andthelong-termgoalofzerofatalities.

• TheSHSPidentifiedsevenprimarysafetyemphasisareasforMinnesota:trafficsafetyculture,safetybelts,impaireddriving,speeding,inattentive,intersectionsandlanedeparture.

• Inurbanareastheprimaryfactorsassociatedwithfatalcrashesareintersectionsandtheuseofsafetybelts;andinruralareastheprimaryfactorsaresafetybelts,impairmentandroaddepartures.

• Acomprehensivesafetyimprovementprocessincludesbothasiteanalysisathighcrashlocationsfocusedonreactiveimplementationofsafetystrategiesandasystemwideanalysisfocusedonproactivelyimplementinggenerallylow-costsafetystrategiesbroadlyacrossprioritylocationsalonganagency’ssystemofroads.

• Therecommendedanalyticalmethodforconductingadetailedstudyofanindividuallocationinvolvescomparingtheactualcrashcharacteristicstotheexpectedcharacteristicsandthenevaluatingthedifferences.Itisimportanttonotethattheexpectedcrashfrequencyofanygivenlocationisneverzero.

• Ofthethreetraditionalmethodsforidentifyingpotentiallyhazardouslocations(numberofcrashes,crashrate,andcriticalcrashrate),thecriticalcrashrateisthemoststatisticallyreliable,butthisisalsothemostdata-intensivemethod.However,theuseofanymethodisbetterthannotconductingaperiodicsafetyinventory.

• Therecommendedmethodforconductingsystemwidesafetyanalysesinvolvesconductingsystemicriskassessments.Thistechniqueisbasedonthepremisethatseverecrashesmaybewidelyscatteredaroundasystem,buttheyarenotran-domlyscattered.Asaresult,areviewoflocationswithseverecrashescanrevealasetofcommonroadwayandtrafficcharacteristics,thepresenceofwhichatlocationswithfewornoseverecrashescanestablishapriorityforsafetyinvest-mentbasedonrisk.

D-4Traffic Safety Fundamentals Handbook – 2015

Lesson Learned – Traffic Safety Tool Box

Highlights• Currenttrafficsafetytoolboxesarebetterstockedandincludeamorecom-

prehensivesetofsafetystrategiesasaresultofeffortsbyNCHRP(Series500Reports),FHWA(CrashModificationFactorsClearinghouse)andAASHTO(HighwaySafetyManual).

• Theselectionofsafetystrategiesbeginswithidentificationofthetypesofcrashesthatarethetargetofmitigationandalsoinvolvesconsiderationoftheexpectedcrashreduction.

• Safetyprogramandhighwaysystemmanagershaveabiasinprojectdevelop-menttowardstrategiesthathavedemonstratedaneffectivenessinreducingcrashes.Thetheoryisthatifastrategyhasbeenprovensuccessfulatreducingcrashesatotherlocations,thatstrategywilllikelyresultinasimilarcrashreductionatyourlocation.

• Strategiesthathaveproventobeeffectivesafetymitigationsinclude:

• Lanedeparturecrashesalongruralroads:improvedroadedgedelineation(edgerumblestripsandwideredgelines),centerlinerumblestrips,andenhancedcurvedelineation(Chevrons).

• Rightanglecrashesatruralthru/STOPintersections:improvedsignsandmarkings,streetlighting,dynamicwarningsigns,reducedconflictintersectionsandroundabouts.

• Rear-endandhead-oncrashesalongurbanroads:roaddietsandaccessmanagement.

• Rightanglecrashesattrafficsignals:confirmationlights.

• Pedestriancrashes:crossingenhancements(countdowntimersandadvancedwalkattrafficsignals,curbextensions,medianrefugeislandsandHAWKsignals)andsidewalks.

• Speedisacontributingfactorinapproximately20%ofseverecrashesandinresponsespeedreductionisfrequentlyrequested.ExperienceinMinnesotaindicatesthatmerelychangingthepostedspeedlimithasneverbeensuccessfulatactuallyloweringoperatingspeeds.Researchsuggeststhatenhancedenforce-ment(sustainedasopposedtoperiodicbecausethehaloeffectisaslittleasafewminutes)andchangingthedriver’sperceptionofthesafespeed(addingurbanfeaturessuchascurbandgutter,boulevard,sidewalks,parkedcars,etc.)haveprovensuccessful.

• Whenconductingasafetyanalysisandespeciallywhendealingwiththepubliconasafetyissue,itisconsideredabestpracticetohavelawenforcementpartici-pateintheseefforts–theyprovideauniqueperspectiveandhelppresentamorecompletepictureofpossiblestrategies–recalldriverbehaviorisacontributingfactorinmorethan90%ofseverecrashes.

Traffic Safety Fundamentals Handbook · 2016-09-16 · professionals in both government agencies...

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Transcript of Traffic Safety Fundamentals Handbook · 2016-09-16 · professionals in both government agencies...