Traffic Control Device Guidelines for Curves

In 2002, there were 38,309 fatal crashes on the U.S. highway system and approximately 25% of these crashes occurred on horizontal curves (NCHRP Report 500: Volume 7, A Guide for Reducing Collisions on Horizontal Curves). Traffic control devices (TCDs) such as signs and delineation treatments are intended to inform and warn motorists of horizontal curves and the Manual on Uniform Traffic Control Devices (MUTCD) is the national standard for all TCDs on roads open to public travel. Research has consistently demonstrated that TCDs on curves are inconsistently applied across the United States (NCHRP Report 559: Communicating Changes in Horizontal Alignment) and the 2009 MUTCD provides more prescriptive requirements than previous editions. The intent of this change was to promote uniformity across the country and, thereby, improve safety on horizontal curves. These MUTCD changes have generated much debate because their impacts on safety or driver behavior have not been documented. While transportation agencies support the goal of reducing crashes, there is concern that installing or replacing TCDs on curves may not be the most cost-effective way of improving safety. There is also concern that installing additional TCDs with limited or no benefit “might result in disrespect at those locations where the device is needed and appropriate.” (2009 MUTCD, Section 1A.06) The objective of this research was to identify potential improvements to the MUTCD guidelines for the application of traffic control devices on curves (particularly curve/turn warning signs, advisory speed plaques, chevrons, and large arrow panels). The improved guidelines include (1) conditions to consider in deciding whether a particular TCD should be installed (e.g., traffic volume, crash history, speed, difference between the posted speed limit and the advisory speed for the curve) and (2) descriptions of appropriate engineering studies, taking into account the variations in staff expertise and resources among local and state transportation agencies. Consistent application of the improved guidelines should lead to (1) reduced road and lane departures on curves, (2) judicious application of TCDs to promote driver compliance and respect, (3) effective allocation of local and state transportation agencies’ budgets for installing and maintaining TCDs, and (4) a limited level of exposure to tort liability suits.


  • English


  • Status: Completed
  • Funding: $500000
  • Contract Numbers:

    Project 03-106

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001
  • Performing Organizations:

    Texas A&M Research Foundation

  • Principal Investigators:

    Carlson, Paul

  • Start Date: 20120619
  • Expected Completion Date: 20150418
  • Actual Completion Date: 20150418

Subject/Index Terms

Filing Info

  • Accession Number: 01746813
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 03-106
  • Files: TRB, RIP
  • Created Date: Jul 27 2020 3:05PM