Study Details
Study Title: Evaluating the Safety Effects of Span Wire to Mast Arm Signal Conversion
Authors: Khattak and Fontaine
Publication Date: 2018
Abstract: The mast arm signal mounting configuration has often been assumed to provide greater conspicuity and visibility than span wire installations, but the impacts of this countermeasure on road safety have not been well established quantitatively. This paper’s intent is to provide a comprehensive evaluation of safety effects of converting span wire installations to mast arm installations. An empirical Bayes before-after safety analysis was conducted using crash data for thirty intersections collected from the Virginia Department of Transportation (VDOT). A crash type analysis was also conducted to observe changes in crash type. Based on the data available, no statistically significant improvement in safety was found. Average crash modification factor (CMF) values of 0.97 and 0.98 were observed for total and fatal and injury crashes, but these CMFs were not statistically significant. While a reduction in the proportion of angle crashes was observed, the change was not statistically significant and the overall distribution of crashes did not change significantly after converting signal configurations from span wire to mast arm. While mast arm deployments may offer advantages in terms of maintenance costs and aesthetics, there does not appear to be a substantial safety benefit to these conversions.
Study Citation: Khattak, Z.H., and M.D. Fontaine. "Evaluating the Safety Effects of Span Wire to Mast Arm Signal Conversion". Presented at the 97th Annual Meeting of the Transportation Research Board, Paper No. 18-01498, Washington, D.C., (2018).
Study Report: Download the Study Report Document
CMFs Associated With This Study
Category: Intersection traffic control
Countermeasure: Convert signal from span wire to mast arm
| CMF | CRF(%) | Quality | Crash Type | Crash Severity | Roadway Type | Area Type |
|---|
| 0.97 | 3 |  | All | All | Not specified | All |
| 0.98 | 2 | | All | K,A,B,C | Not specified | All |
| 0.97 | 3 | | Angle | K,A,B,C | Not specified | All |
| 0.95 | 5 | | Angle | All | Not specified | All |
| 1 | 0 | | Rear end | All | Not specified | All |
| 1.2 | -20 | | Rear end | K,A,B,C | Not specified | All |
| 0.98 | 2 | | All | All | Not specified | Urban and suburban |
| 1.03 | -3 | | All | K,A,B,C | Not specified | Urban and suburban |
| 0.99 | 1 | | All | All | Not specified | All |
| 1 | 0 | | All | K,A,B,C | Not specified | All |
| 1 | 0 | | All | All | Not specified | Urban and suburban |
| 1.09 | -9 | | All | K,A,B,C | Not specified | Urban and suburban |
