1. Design Vehicle CE 453 Lecture 6

2. 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. 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. 4 Dimensions of Design Vehicles

5. 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. 6 Environmental Characteristics ► Noise (noise meter) ► Exhaust ► Fuel Efficiency ► Dust (particulate and VOCs from tires and brakes)

7. 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/ta ble%20of%20contents.htm for Chicago’s PACE design guide http://www.pacebus.com/sub/guidelines/development_guidelines/ta ble%20of%20contents.htm http://www.pacebus.com/sub/guidelines/development_guidelines/ta ble%20of%20contents.htm  School Bus – low vol county, state hwy  WB series – freeway ramp, arterial and state hwy, industrial areas, US and Interstate Highways

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

9. 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/p roducts/at/product_feat.asp

10. 10 Minimum Turning Radii

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12. 12 Offtracking ► Rear wheels do not follow path of front wheels ► Increases with size of vehicle ► Decreases with radius of curve

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14. 14 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

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17. 17 Double 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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19. 19Widening ► 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:

20. 20 Effect of grade on truck performance

21. 21 Effect of grade on RV performance

22. 22 Effect of differential speed on crash rate

23. 23 Critical Grade ► % AND length of grade where “typical” trucks can maintain a “safe” speed See also: Highway Capacity Manual

24. 24 Friction

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