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Iowa State University--Becoming the Best

Development of Crash Modification Factors for Curve Chevrons


Principal investigators:

Project status

In progress

Start date: 05/01/13
End date: 04/30/16


Sponsor(s): Iowa Department of Transportation

About the research


BACKGROUND Chevrons provide additional emphasis and guidance for drivers. If properly spaced, chevrons can delineate the curve so that drivers are better able to gauge the sharpness of the curve. Section 2C.04 of the MUTCD (2009) covers chevron alignment sign (Wl-8) size. Several agencies, have applied a larger chevron size than suggested by the MUTCD. The idea is that larger chevrons will be more prominent and visible to drivers. These larger chevrons may be particularly useful if sight distance issues exist. Only a limited number of studies have evaluated the crash effectiveness of chevrons. Washington installed chevrons at sites where chevrons were not previously posted, as well as increased the number of chevrons at locations where they were already present and reported a reduction in several crash types. For instance, lane departure crashes decreased by 5.9% (FHWA 2009). However, crash modification factors (CMFs) were not developed. A study by Montella (2009) evaluated a combination of chevron signs, curve warning signs, and or sequential flashing beacons and developed crash modification factors. However the CMFs were for the combination of treatments and were not specific to just chevrons. Two studies were available where CMFs were developed. Srinivasan et al (2009) developed CMF for chevrons on head-on and nonintersection run-off-road crashes which included all roadway types and (CMF = 0.94) and Lalani (1991) developed CMF for chevrons on minor arterials (CMF = 0.36). No studies were available which evaluated the effectiveness of oversized chevrons. OBJECTIVES The objective of this study is to develop crash modification factors for regular and oversized chevrons