Design speed is used in selecting the vertical and horizontal elements for new roadways while speed limits are based on a statistical analysis of individual vehicular speeds. At some locations, the speed limit based on an 85th percentile speed exceeds the roadway's design speed. This situation is a result of the fact that criteria used in highway design incorporate a significant factor of safety - i.e., roadways are designed for near worst-case conditions. When posted speed exceeds design speed, however, liability concerns arise even though drivers can safely exceed the design speed. Research conducted in this project clearly indicated that DOT officials are concerned with the potential liability; however, only a few of the respondents to surveys and interviews actually experienced a lawsuit relevant to the design speed-posted speed issue. The respondents indicated that the primary liability concern rests with the current AASHTO definition of design speed. If the definition were changed to reflect its actual meaning, then liability concern would be reduced substantially. During this project, researchers conducted field studies on suburban highways at horizontal curves and limited sight distance crest vertical curves.
Compatibility of Design Speed, Operating Speed, and Posted Speed
1995
117 pages
Report
Keine Angabe
Englisch
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