Citation

Simpson C, Troy S. Transp. Res. Rec. 2013; 2384: 1-9.

Copyright

(Copyright © 2013, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

10.3141/2384-01

PMID

unavailable

Abstract

This project evaluated the safety effectiveness of "Vehicle Entering When Flashing" (VEWF) intersection conflict warning systems (ICWSs) at stop-controlled intersections. The North Carolina Department of Transportation has utilized this treatment, which consists of vehicle-actuated sign and flasher assemblies placed at or near the intersection to warn motorists on the major or minor road, or both, of vehicles entering the intersection. Although this countermeasure has been used for years in North Carolina, and similar ICWSs have been used in other states, there has been minimal safety evaluation to prove or validate the systems' effectiveness. This study evaluated four categories of VEWF systems. Sites were categorized on the basis of the direction of the alert and placement from the intersection. Crash modification factors (CMFs) were provided for all sites and each category, as well as exclusively for sites with two-lane at two-lane intersections. Empirical Bayes before-and-after techniques were used to overcome the regression to the mean threat. Deployments with major road alerts in advance of the intersection and a combination of both major and minor road alerts were determined to be most effective for two-lane at two-lane stop-controlled intersections with CMFs for total crashes of 0.68 and 0.75, respectively.