Study Details

Study Title: Safety Evaluation of Two Curve Warning Treatments: In-Lane Curve Warning Pavement Markings and Oversized Chevron Signs

Authors: Lyon et al.

Publication Date: JAN, 2017

Abstract: The objective of this study was to undertake a rigorous before-after evaluation of the safety effectiveness—as measured by crash frequency—of in-lane pavement marking curve warnings and oversized chevrons in horizontal curves. These strategies were selected for the investigation for the Evaluation of Low Cost Safety Improvements Pooled Fund Study, which functions under the US Federal Highway Administration’s Development of Crash Modification Factors program. Data from four states, Iowa, Kansas, Missouri and Pennsylvania were used to estimate crash modification factors (CMFs) for specific crash types including total, fatal+injury, run-off-road, night and night run-off-road using the empirical Bayes (EB) methodology. For in-lane curve warning pavement markings, results indicate that only the CMF estimates for total and night crashes are statistically significant at the 95-percent confidence limit. However, no CMF is recommended at this time since these results are based on few crashes in the after period and should be used with due caution. The sample size for oversized chevron signs was larger but still modest. None of combined results were statistically significant at the 95-percent confidence level. However, the estimated CMF of 0.73 for night crashes, the target crash type, has a relatively low p-value of 0.11. The disaggregate results for this crash type suggest, that sites where advisory speeds have been posted because of a combination of sharper curvature and higher design speeds may yield higher benefit from the installation of chevrons, especially larger chevrons, when compared to locations where advisory speeds are not required.

Study Citation: Lyon, C., B. Persaud, and K. Eccles. "Safety Evaluation of Two Curve Warning Treatments: In-Lane Curve Warning Pavement Markings and Oversized Chevron Signs". Presented at the 96th Annual Meeting of the Transportation Research Board, Paper No. 17-00432, Washington, D.C., (2017).


CMFs Associated With This Study

Category: Delineation

Countermeasure: Install in-lane curve warning pavement markings

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.616 38.4 4 Stars All All Not specified
1.01 -1 3 Stars All K,A,B,C Not specified
1.67 -67 3 Stars Run off road All Not specified
0.649 35.1 3 Stars Nighttime All Not specified
0.647 35.3 3 Stars Other All Not specified

Category:Signs

Countermeasure: Install oversized chevron signs

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.946 5.4 4 Stars All All Not specified Not specified
0.852 14.8 4 Stars All K,A,B,C Not specified Not specified
1.061 -6.1 4 Stars Run off road All Not specified Not specified
0.731 26.9 4 Stars Nighttime All Not specified Not specified
0.756 24.4 3 Stars Other All Not specified Not specified
0.56 44 3 Stars Nighttime All Not specified Not specified
0.89 11 3 Stars Nighttime All Not specified Not specified