Study Details
Study Title: An Evaluation of the Safety Effects of Modifying Late Night Flash Signal Operations in North Carolina
Authors: Murphy
Publication Date:JAN, 2009
Abstract: In February of 2004, the North Carolina Department of Transportation (NCDOT) revised their statewide late night flash policy to make it standard practice that signals operate in steady mode at all times. Before this policy, it was standard practice to allow traffic signals to operate in late night flash mode unless directed otherwise by the Division Traffic Engineer. The policy also changed the standard operating times for late night flash operations. As a result of this policy, many signals were either removed from late night flash operations or had their late night flash operating times modified to conform to the new policy. The purpose of this project is to develop crash reduction factors for late night flash operation modifications. The particular modifications studied in this project were removing late night flash operations completely and modifying the time periods in which late night flash was allowed to operate. A total of 67 sites where late night flash operations were removed were utilized for this study. In addition, 145 sites where late night flash run times were modified were considered. Four hundred and sixty eight reference sites were selected and the Empirical Bayes method of sample moments was carried out to calculate the necessary crash reduction parameters. On the average, all categories of crashes considered in this study showed a decrease in the after period. As expected, more of a decrease was seen at the sites where late night flash was removed completely.
Study Citation: Murphy, B., "An Evaluation of the Safety Effects of Modifying Late Night Flash Signal Operations in North Carolina." TRB 88th Annual Meeting Compendium of Papers CD-ROM. Washington, D.C., (2009).
CMFs Associated With This Study
Category: Intersection traffic control
Countermeasure: Modify night-time flash operation period
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.88 | 12 |  | All | All | Not Specified |
| 0.84 | 16 | | All | K,A,B,C | Not Specified |
| 1 | 0 | | Frontal and opposing direction sideswipe,Head on | All | Not Specified |
Countermeasure: Replace Night-Time Flash with Steady Operation
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|---|---|---|---|---|---|
| 0.73 | 27 |  | All | All | Not Specified |
| 0.77 | 23 | | All | K,A,B,C | Not Specified |
| 0.52 | 48 | | Frontal and opposing direction sideswipe,Head on | All | Not Specified |
