Subject: a
From: <Saved by Windows Internet Explorer 7>
Date: Sun, 29 Mar 2009 20:15:24 -0700

a.  Design Vehicle.  The vehicle frequently using the

road that determines the minimum standard for a

particular design element.  No single vehicle controls

the standards for all the design elements for a road.

Determine the maximum and minimum standards from the type

and configuration of the vehicles using the road.

Analyze each design element to determine which vehicle

governs the standard for that element.  Following are

some examples:

Design Element                        Possible Design Vehicle

Stopping sight distance           Passenger car or pickup

Thickness of pavement structure

(1)  Campgrounds                 Garbage or other service truck

(2)  Logging road              Yarding equipment or construction equipment

Curve widening                       Log truck, lowboy or gravel truck

Lateral or vertical clearance      Yarding equipment, lowboys, chip vans

Gradient                                    Gravel truck or recreation vehicles

b.  Critical Vehicle

(1)  The vehicle, normally the largest (by weight, size,

or unique configuration), whose limited use on the road

is necessary to complete the planned activity.

Critical vehicle examples:

(a)  Log yarder on a timber access road.

(b)  Semi trailer truck carrying construction equipment on a recreation access road.

(c)  Overlength, over-width semi-trailer trucks carrying drill rig components on a minerals access road.

(d)  Construction equipment used to build the facility.

(e)  Recreation vehicles, such as large motorhomes, with

or without other vehicles in tow.

(2)  Depending on the traffic service level of the road,

special design provisions, operational considerations, or

a combination of both may accommodate critical vehicles.

c.  Design and Critical Vehicle Analysis.  Consider both

the equipment needed to construct the road and the equipment

that will use the completed road.