Study Details

Study Title: Evaluation of the Safety Effectiveness of "Vehicle Entering When Flashing" Signs and Actuated Flashers at 74 Stop-Controlled Intersections in North Carolina

Authors: Simpson and Troy

Publication Date:JAN, 2013

Abstract: The purpose of this project is to evaluate the safety effectiveness of "Vehicle Entering When Flashing" (VEWF) intersection conflict warning systems at stop-controlled intersections. North Carolina Department of Transportation (NCDOT) has utilized this treatment consisting of vehicle actuated sign and flasher assemblies placed at or near the intersection to warn motorists on the major and/or minor road of vehicles entering the intersection. Although this countermeasure has been used for years in North Carolina, and similar intersection conflict warning system have been used in other States, there has been minimal safety evaluation to prove or validate its effectiveness. Four categories of VEWF systems are evaluated. Sites are categorized based on the direction of the alert and placement from the intersection. Crash modification factors (CMFs) are provided for all sites and each category, as well as exclusively for sites with two-lane at two lane intersection configurations. Empirical Bayes before and after techniques were utilized 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.

Study Citation: Simpson, C.L., and S.A. Troy. "Evaluation of the Safety Effectiveness of 'Vehicle Entering When Flashing' Signs and Actuated Flashers at 74 Stop-Controlled Intersections in North Carolina". Presented at the 92nd Annual Meeting of the Transportation Research Board, Washington, D.C., Paper No. 13-1159, (2013).


CMFs Associated With This Study

Category: Signs

Countermeasure: Install a "Vehicles Entering When Flashing" (VEWF) system (advance post mounted signs on major and loops on minor)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.68324 StarsAllAllNot specifiedAll
0.68324 StarsAngle,Head on,Left turn,Right turnAllNot specifiedAll
0.73274 StarsAllK,A,B,CNot specifiedAll
0.7303 StarsAllK,ANot specifiedAll

Countermeasure: Install a "Vehicles Entering When Flashing" (VEWF) system (combination of overhead and advance post mounted signs)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.75253 StarsAllAllNot specifiedAll
0.8203 StarsAngle,Head on,Left turn,Right turnAllNot specifiedAll
0.87133 StarsAllK,A,B,CNot specifiedAll
0.24763 StarsAllK,ANot specifiedAll

Countermeasure: Install a "Vehicles Entering When Flashing" (VEWF) system (overhead signs at intersection on major and loops on minor)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.06-63 StarsAllAllNot specifiedAll
1.07-73 StarsAngle,Head on,Left turn,Right turnAllNot specifiedAll
0.9283 StarsAllK,A,B,CNot specifiedAll
0.61393 StarsAllK,ANot specifiedAll

Countermeasure: Install a "Vehicles Entering When Flashing" (VEWF) system (overhead signs at intersection on minor and loops on major)

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
0.9553 StarsAllAllNot specifiedAll
103 StarsAngle,Head on,Left turn,Right turnAllNot specifiedAll
0.9373 StarsAllK,A,B,CNot specifiedAll
0.76243 StarsAllK,ANot specifiedAll