01049284

Component

Horizontal curves are essential elements in any highway system, but crash statistics have consistently shown sharp curves to be safety hazards for drivers. Since it is not economically feasible to straighten all sharp curves, it is necessary to use traffic control devices to warn drivers of the need to reduce speed before they enter curves. Providing effective warning requires both a good understanding of typical driver behavior in horizontal curves and the consistent application of reasonable criteria to determine posted advisory speeds. In this paper, a synthesis is provided of documented research on the relationship between curve speeds and key design and operational variables like radius, approach tangent speed, superelevation rate, and vehicle type. Summary is also provided of current advisory speed setting practices. It is shown that curve advisory speeds posted in the field generally do not agree with the speeds that should be posted based on agency policies, and that agency policies generally produce advisory speeds that are too low for passenger vehicles. These two problems make it difficult for drivers to develop expectancies on curve sharpness, and thus undermine the purpose of the advisory speed plaques. The practice would benefit from the adoption of new advisory speed criteria that more closely match driver speed choice through curves, and the consistent application of these criteria.

01042056

07-1709

English

17p

2007

Transportation Research Board 86th Annual Meeting

CD-ROM

Figures (7) ; References (33) ; Tables (2)

Behavior; Curves (Geometry); Highway curves; Highway design; Highway operations; Operations; Speed limits; Superelevation; Traffic speed

Horizontal curvature; Vehicle type

Administration and Management; Highways; Operations and Traffic Management; Planning and Forecasting; Safety and Human Factors; I72: Traffic and Transport Planning

Transportation Research Board Annual Meeting 2007 Paper #07-1709

TRIS, TRB

Feb 8 2007 6:23PM