03 CE 122 Highway Location

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Pertains to the acquisition of data concerning the terrainupon which the transportation links will traverse and theeconomical siting of an alignment.

Possible routes can be chosen and evaluated on the basisof traffic service, directness, suitability of terrain, adequacy ofcrossings of streams and other transport routes and extent ofadverse social, environmental and ecological effects.

Possible alternative alignments usually are plotted on thebase map and, from these alignments with preliminarygradelines, the alternatives are compared.

10/14/2011CE 122- Traffic & Highway Engineering: Highway Location


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Criteria Influencing FactorsConstruction costs Functional classification/design type; topography and

soil conditions; current land useUser costs Traffic volume; facility design features (e.g., gradients

intersections);operating conditions (e.g., speeds,traffic control systems)

Environmental impacts Proximity to sensitive areas; design features to mitigImpacts

Social impacts Isolation or division of neighborhoods; aesthetics of

Design; fostering of desired development patterns Acceptance by various Government agencies; private associations and firmsInterest groups neighborhood groups and the general public


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For new major highways, locations must blendcurvatures, grade and other roadway elements toproduce an easy-riding, free-flowing traffic artery thathas high capacity and meets exacting safety standardswhile minimizing disruption to historic and archaeological

sites and to community, industrial, business, residential, scenic, and recreational developments. Economic andenvironmental impacts must be evaluated.

A general practice is to select a location, which will

permit the construction of a highway to the standards ofgrade , alignment , width and sight distance based uponprobable future traffic over a period of 25 years ( 20 yearsis commonly used).



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DeskStudy ofthe Area

Reconnai-ssanceSurvey

RouteSelection

Prelimina-ry

LocationSurvey

FinalLocation

Survey



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The possible desk study for highway of an area include;

Maps, Aerial photographs, charts or graphs to obtains, engineeringdata, environmental data, social data, economic data.


ENGINEERINGDATA:

ENVIRONMENTALDATA:

SOCIAL DATA: ECONOMIC DATA:

Topographic and

geological maps

Agricultural soil

surveys indicating soilerodiability

Demographic and

land use information

Overall cost of

previous projects

Stream anddrainage basin maps

Air pollution studies Census data Unit constructioncosts data

Climatic records Noise and noiseattenuation studies

Zoning plans andtrends

Agricultural,economical andindustrial data etc

Preliminary surveymaps of previousprojects

Fish and wild lifeinventories

Building permitrecords, motorvehicle registrationrecords

Traffic surveys andcapacity studies

Historical studies Living standards oflocality


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This eliminates costly locations and limits the choice to one or two generalroutes between controls. This could be aided effectively by the study ofavailable maps, examination of the ground as viewed from an airplane,stereoscopic examination of aerial photographs, and ocular examination ofthe site on foot.Two methods;

Conventional ground method. Aerial photography.

Reconnaissance Report: Total length of line. The elevation of main and intermediate summit All adverse grades. Stream crossing. Nature of construction. Right of way circumstances. Soil conditions. Unusual or troublesome condition. Approximate estimate of cost.


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Before field survey for any highway location is started, tentativedecision, regarding the design speed of the route, its cross-section, and the maximum grade must be made. Thesedecision made are based on the;

Estimated of amount, character and hourly distribution oftraffic, along with

Knowledge of the area is traversed. And available funds.

RESULTING ROUTE: After comparison of the different alternativedesign, the route is selected which has cheapest overall cost,considering capital investment, maintenance, expense and

saving to the road user.




Conventionally the baseline of preliminary survey i.e. P-line shouldfollow as closely as possible to the expected final line. The surrounding are then related to this P-line. Elevations - At 100ft and at breaks in the ground provide data for profileand serve as starting point for cross-sections that covers a strip of land oneach side of P-line.

Cross-section - are of width 100 to 800, depending upon; Standard of accuracy Speed of work and instrument used.

However accurate measurements are used for checking the accuracyof final location.

The next step is to plot plan and profile of the preliminary line.



Final location is essentially fixing of the details of the projected highway. Itserves the dual purpose of :

Permanently establishing the centerline. Collecting information necessary for preparation of plans forconstruction. The line should be established as closely as is practical to the line drawnon the preliminary map. It should conform the major and minor controlpoints and the alignment that was previously determined. Staking out on the ground of the centerline of the projected roadprovides opportunity for minor correction like small shift of the line. It is useful to make a new profile and accurate cross-section from whichexcavation and embankment quantities can be measured. Sufficient points of curvature and tangency, BMs at relatively closeinterval and in position free from disturbance by construction activities.



Direction of all property lines, distance to property corners and location ofbuilding, fences and other improvements. It is important to keep notes on alignment and levels i.e. notes taken infield during the final location survey usually becomes part of permanentrecord. The final location survey is complete when all necessary information inavailable and ready for designer to use. It in insured that all informationrequired preparation of complete construction. All information pertaining to

Alignment Topography Bench mark levels Cross sections Section corner ties and other land ties Drainage and utilities


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Type ofHighway

Design Speedmph (kph)

Horizontal Curve*(Maximum Degree)

Vert. CurvesMin. K-

SSD**

MaximumGrade (%)

Freeway*** 70 (110 kph) 3 255 (78 m) 4

Other Principal 60 (100 kph 5 160 (49 m) 4 Arterial 50 (80 kph) 7 85 (26 m) 5

Minor Arterial 40 (60 kph) 11 55 (17 m) 6Collector 30 50 kph) 21 28 ( 9 m) 7* Based on e = 0.06** K = L/A = Horizontal distance (ft.) / % change in slope

*** Design speed may range from 50-70 mph; Where < 70 mph, lower design value maybe used.


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Type of Highway Design Speed,miles/hr, mph

Trial Service Volumeveh./lane/hour

Freeway 70 (110 kph) 1,300

Other PrincipalArterial

60 (100 kph) 800 *

50 (80 kph) 500 **

Minor Arterial 40 (60 kph) 300 ***

Collector 30 (50 kph) 200 ***

* Assuming 60% Green time** Assuming no parking and 45% green time***Assuming parking and 30% green time


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03 CE 122 Highway Location

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