Crash Modification Factors for Chevrons in Iowa

Although chevron alignment signs have been utilized for some time along horizontal curves, their effectiveness is not well documented. The Crash Modification Factors Clearinghouse includes crash modification factors (CMFs) for chevrons from 0.41 to 1.92 (FHWA 2015). The lack of documentation on the effectiveness of chevrons and the range of values for CMFs make it difficult for agencies to estimate the cost effectiveness of chevrons. As a result, the objective of this study was to develop a CMF for chevron alignment signs that can be used by Iowa agencies to help address crashes on curves. Although chevron alignment signs have been utilized for some time along horizontal curves, their effectiveness is not well documented. The Crash Modification Factors Clearinghouse includes crash modification factors (CMFs) for chevrons from 0.41 to 1.92 (FHWA 2015). The lack of documentation on the effectiveness of chevrons and the range of values for CMFs make it difficult for agencies to estimate the cost effectiveness of chevrons. As a result, the objective of this study was to develop a CMF for chevron alignment signs that can be used by Iowa agencies to help address crashes on curves. The results of the study did not reflect the safety benefits of the chevron sites effectively. The study encountered issues common to cross-sectional studies such as the fact that higher crash locations are more likely to have the countermeasure being studied. Moreover, it was also seen that the effect of radius was more significant on treatment curves than control curves. This suggests that chevrons were targeted to high crash locations and the effect cannot be well captured using a cross-sectional analysis.

• Record URL:
  • https://intrans.iastate.edu/app/uploads/2018/02/chevron_cmfs_tb.pdf
• Summary URL:
  • https://intrans.iastate.edu/research/completed/development-of-crash-modification-factors-for-curve-chevrons/
• Corporate Authors:

  Iowa State University, Ames

  Center for Transportation Research and Education
  2711 South Loop Drive, Suite 4700
  Ames, IA  United States  50010-8664

  Iowa State University, Ames

  Institute for Transportation
  Ames, IA  United States  50010-8664

  Midwest Transportation Center

  Iowa State University
  2711 S Loop Drive, Suite 4700
  Ames, IA  United States  50010-8664

  Iowa Department of Transportation

  800 Lincoln Way
  Ames, IA  United States  50010

  Department of Transportation

  Office of the Assistant Secretary for Research and Technology
  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Hallmark, Shauna L
  • 0000-0001-5187-8022
  • Goswamy, Amrita
  • 0000-0003-0113-3094
• Publication Date: 2018-2

Language

• English

Media Info

• Media Type: Digital/other
• Features: Maps; Photos; References; Tables;
• Pagination: 6p
• Serial:
  • Tech Brief
  • Publisher: Iowa State University, Ames

Subject/Index Terms

• TRT Terms: Crash modification factors; Cross sectional studies; Highway curves; Traffic signs; Warning signs
• Geographic Terms: Iowa
• Subject Areas: Highways; Operations and Traffic Management; Safety and Human Factors;

Filing Info

• Accession Number: 01837710
• Record Type: Publication
• Files: TRIS, ATRI, USDOT, STATEDOT
• Created Date: Feb 28 2022 9:41AM