Design Vehicle

Design VehicleDesign Vehicle

CE 453 Lecture 6CE 453 Lecture 6

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Design VehicleDesign Vehicle►Design Vehicle – largest (slowest, Design Vehicle – largest (slowest,

loudest?) vehicle likely to use a facility loudest?) vehicle likely to use a facility with considerable frequencywith considerable frequency

►Three characteristics that affect Three characteristics that affect almost all aspects of highway designalmost all aspects of highway design PhysicalPhysical OperatingOperating EnvironmentalEnvironmental

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Physical CharacteristicsPhysical Characteristics

► Type (GB defines 20 design vehicle types)Type (GB defines 20 design vehicle types) Passenger Car PPassenger Car P Buses BBuses B Trucks SU, WBTrucks SU, WB RVsRVs Farm tractorFarm tractor

► Size Size LengthLength HeightHeight WeightWeight WidthWidth Height of driver’s eye (car: 3.5’ – avg., truck: 7.6’ – high Height of driver’s eye (car: 3.5’ – avg., truck: 7.6’ – high

side)side) Center of massCenter of mass

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Dimensions of Design Dimensions of Design VehiclesVehicles

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Operating CharacteristicsOperating Characteristics

► AccelerationAcceleration► Deceleration and brakingDeceleration and braking► Power/weight ratiosPower/weight ratios► Turning radiusTurning radius► OfftrackingOfftracking► Headlights (2’ … truck Headlights (2’ … truck

driver/retroreflectivity?)driver/retroreflectivity?)► Friction (ball bank)Friction (ball bank) http://www.cable-car-guy.com/images/ih_truck_ad_dec_1926.jpg

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Environmental Environmental CharacteristicsCharacteristics

► Noise (noise meter)Noise (noise meter)► ExhaustExhaust► Fuel EfficiencyFuel Efficiency► Dust (particulate and VOCs from tires Dust (particulate and VOCs from tires

and brakes)and brakes)

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Selection of Design VehicleSelection of Design Vehicle

► Key ControlsKey Controls Physical and OperatingPhysical and Operating

► Key FactorsKey Factors Proportion and FrequencyProportion and Frequency

► Key TypesKey Types Car – parking lotCar – parking lot SU Truck – res. Intersections, park roadsSU Truck – res. Intersections, park roads City Bus – state hwy, city street, bus routeCity Bus – state hwy, city street, bus route

► See See http://www.pacebus.com/sub/guidelines/development_guidehttp://www.pacebus.com/sub/guidelines/development_guidelines/table%20of%20contents.htmlines/table%20of%20contents.htm for Chicago’s PACE design guide for Chicago’s PACE design guide

School Bus – low vol county, state hwySchool Bus – low vol county, state hwy WB series – freeway ramp, arterial and state hwy, WB series – freeway ramp, arterial and state hwy,

industrial areas, US and Interstate Highwaysindustrial areas, US and Interstate Highways

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State and Local Truck LimitsState and Local Truck Limits

► See See Colorado Truck Legal DimensionsColorado Truck Legal Dimensions► See See

http://www.dot.state.ia.us/mvd/omve/truckghttp://www.dot.state.ia.us/mvd/omve/truckguide.pdfuide.pdf for Iowa Truck Guide for Iowa Truck Guide

► See See http://www.co.jasper.ia.us/new_page_7.htmhttp://www.co.jasper.ia.us/new_page_7.htm for Jasper County permit requirementsfor Jasper County permit requirements

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Turn PathsTurn Paths

►Key variables in turn pathsKey variables in turn paths Centerline turn radiusCenterline turn radius Out-to-out trackOut-to-out track WheelbaseWheelbase Path of inner tirePath of inner tire

►See Autoturn Software Page See Autoturn Software Page http://www.transoftsolutions.com/transhttp://www.transoftsolutions.com/transoft/products/at/product_feat.aspoft/products/at/product_feat.asp

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MinimuMinimum m Turning Turning RadiiRadii

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OfftrackingOfftracking

►Rear wheels do not follow path of front Rear wheels do not follow path of front wheelswheels

► Increases with size of vehicleIncreases with size of vehicle►Decreases with radius of curveDecreases with radius of curve

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Front Overhang and Front Overhang and Difficulty Adjustment (Z)Difficulty Adjustment (Z)

►Radial distance between outside front Radial distance between outside front wheel path and outside front wheel path and outside front bumper/fenderbumper/fender

► Extra width allowance (Z) for difficulty Extra width allowance (Z) for difficulty in maneuveringin maneuvering

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17Double for 4 ln undivided. Values less than 2’ may be neglected.

Total widening recommended (includes front overhang, offtracking and difficulty adj.)

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WideningWidening►Widen inside only when not using Widen inside only when not using

spiral (split even if using spirals)spiral (split even if using spirals)►Paint CL and joint at middle of Paint CL and joint at middle of

pavementpavement►Transition over superelevation Transition over superelevation

transitiontransition►Green book terminology:Green book terminology:

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Effect of grade on truck Effect of grade on truck performanceperformance

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Effect of grade on RV Effect of grade on RV performanceperformance

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Effect of differential speed on crash Effect of differential speed on crash raterate

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Critical GradeCritical Grade►% AND length of grade where “typical” % AND length of grade where “typical”

trucks can maintain a “safe” speedtrucks can maintain a “safe” speedSee also: Highway Capacity Manual

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FrictionFriction

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