Design vehicle is defined by ITE as the vehicle that must regularly be accommodated on a roadway without encroachment into other travel lanes. The design vehicle’s dimensions and movements can play a large role in the physical characteristics of a roadway, such as the appropriate lane width and the radii of curves at intersections and driveway corners.
AASHTO has developed several profiles for commonly-used design vehicles, the details of which are provided in Chapter 2 of AASHTO’s Policy on the Geometric Design of Highways and Streets. The profiled design vehicles range in size from passenger cars to interstate tractor-trailers. Larger design vehicles require larger roadway dimensions, particularly at intersections.
There are a number of tradeoffs inherent in design vehicle selection. The design vehicle selected for a given roadway should represent the largest vehicle that regularly or frequently, not occasionally, uses it. Selecting too large a design vehicle for a roadway or roadway segment will result in wider lanes and intersections, jeopardizing safety for other modes and leaving less space for pedestrian, bicycle and transit infrastructure.
Selecting too small a design vehicle can make turning maneuvers difficult or impossible for larger vehicles, potentially causing congestion and/or safety issues. Balancing these tradeoffs is an essential component of creating a great street which adequately serves regular users and is appropriate for the place type.
Design Vehicle for Neighborhood Shop Areas:
Several characteristics influence design vehicle selection for neighborhood shop thoroughfares:
Select the smallest practical design vehicle.
Neighborhood shop place types should not be designed to accommodate large vehicles. These types of areas are typically comprised of numerous small parcels or densely-developed larger parcels that rely on pedestrian traffic for business and access. Choosing the smallest practical design vehicle (the largest vehicle that regularly uses the facility) for these place types can produce a number of benefits, including:
Plan and design for bus access.
Because buses are not uncommon in neighborhood shop areas, it is important to coordinate with regional transit agencies to determine the appropriate dimensions and considerations if a bus is to be the facility’s design vehicle. Special attention is required if articulated buses are expected to use the arterial, as these buses have different design requirements than standard buses.
Strategically design for truck access.
Large trucks are a component of commerce and shipping and though they would ideally be rerouted to mobility-oriented arterials, there may still be a need to accommodate large trucks delivering goods and materials to businesses along neighborhood shop thoroughfares. The following design criteria can improve access for large trucks in these place types:
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