There is no requirement that PSD be provided for any two-lane road. Where it is possible to provide, PSD enhances the operation of the road, but it is not normally considered a "safety essential" design feature. Furthermore, PSD applies only to two-lane highways, and is not considered in the design of multilane facilities.

There is no requirement that PSD be provided for any two-lane road. Where it is possible to provide, PSD enhances the operation of the road, but it is not normally considered a "safety essential" design feature. Furthermore, PSD applies only to two-lane highways, and is not considered in the design of multilane facilities.

Research has demonstrated that AASHTO PSD values are conservative. Many drivers readily accept and safely execute passing maneuvers over shorter distances than are specified by the AASHTO Green Book (2). Indeed, the Manual on Uniform Traffic Control Devices (MUTCD) uses shorter distances than AASHTO values for the marking of passing zones.

From A Guide for Achieving Flexibility in Highway Design, 2004, by the American Association of State Highway and Transportation Officials, Washington, D.C. Used by permission. AASHTO publications may be purchased from that organization's bookstore at 1-800-231-3475 or online at http://bookstore.transportation.org.

External Links:

Purchase this Excerpt »