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Design Vehicle

Design Vehicle. CE 453 Lecture 6. Design Vehicle. Design Vehicle – largest (slowest, loudest?) vehicle likely to use a facility with considerable frequency Three characteristics that affect almost all aspects of highway design Physical Operating Environmental. Physical Characteristics.

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Design Vehicle

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  1. Design Vehicle CE 453 Lecture 6

  2. Design Vehicle • Design Vehicle – largest (slowest, loudest?) vehicle likely to use a facility with considerable frequency • Three characteristics that affect almost all aspects of highway design • Physical • Operating • Environmental

  3. Physical Characteristics • Type (GB defines 20 design vehicle types) • Passenger Car P • Buses B • Trucks SU, WB • RVs • Farm tractor • Size • Length • Height • Weight • Width • Height of driver’s eye (car: 3.5’ – avg., truck: 7.6’ – high side) • Center of mass

  4. Dimensions of Design Vehicles

  5. Operating Characteristics • Acceleration • Deceleration and braking • Power/weight ratios • Turning radius • Offtracking • Headlights (2’ … truck driver/retroreflectivity?) • Friction (ball bank) http://www.cable-car-guy.com/images/ih_truck_ad_dec_1926.jpg

  6. Environmental Characteristics • Noise (noise meter) • Exhaust • Fuel Efficiency • Dust (particulate and VOCs from tires and brakes)

  7. Selection of Design Vehicle • Key Controls • Physical and Operating • Key Factors • Proportion and Frequency • Key Types • Car – parking lot • SU Truck – res. Intersections, park roads • City Bus – state hwy, city street, bus route • See http://www.pacebus.com/sub/guidelines/development_guidelines/table%20of%20contents.htm for Chicago’s PACE design guide • School Bus – low vol county, state hwy • WB series – freeway ramp, arterial and state hwy, industrial areas, US and Interstate Highways

  8. State and Local Truck Limits • See Colorado Truck Legal Dimensions • See http://www.dot.state.ia.us/mvd/omve/truckguide.pdf for Iowa Truck Guide • See http://www.co.jasper.ia.us/new_page_7.htm for Jasper County permit requirements

  9. Turn Paths • Key variables in turn paths • Centerline turn radius • Out-to-out track • Wheelbase • Path of inner tire • See Autoturn Software Page http://www.transoftsolutions.com/transoft/products/at/product_feat.asp

  10. Minimum Turning Radii

  11. Offtracking • Rear wheels do not follow path of front wheels • Increases with size of vehicle • Decreases with radius of curve

  12. Front Overhang and Difficulty Adjustment (Z) • Radial distance between outside front wheel path and outside front bumper/fender • Extra width allowance (Z) for difficulty in maneuvering

  13. Total widening recommended (includes front overhang, offtracking and difficulty adj.) Double for 4 ln undivided. Values less than 2’ may be neglected.

  14. Widening • Widen inside only when not using spiral (split even if using spirals) • Paint CL and joint at middle of pavement • Transition over superelevation transition • Green book terminology:

  15. Effect of grade on truck performance

  16. Effect of grade on RV performance

  17. Effect of differential speed on crash rate

  18. Critical Grade • % AND length of grade where “typical” trucks can maintain a “safe” speed See also: Highway Capacity Manual

  19. Friction

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