Design Speed and Operating Speed in Rural Highway Alignment Design

The relationship between design speeds and operating speeds on twolane rural highway alignments is evaluated. The current policy on design speed and its origins is described, and empirical evidence of disparities between design speeds and operating speeds are presented. U.S. policy on selecting and applying design speeds is critiqued, modifications to the design-speed concept in Australia and Europe are discussed, and possible revisions to U.S. policy on design speed are identified.