Curve Speeds and Advisory Speed-Setting Criteria

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.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 17p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01049284
  • Record Type: Publication
  • Report/Paper Numbers: 07-1709
  • Files: TRIS, TRB
  • Created Date: Feb 8 2007 6:23PM