Study Details

Study Title: Crash Modification Factors for Median Cable Barriers in Tennessee

Authors: Bryant

Publication Date: JAN, 2018

Abstract: This paper developed Crash Modification Factors (CMF) for median cable barriers in Tennessee. Utilizing cable barriers installed from 2006 to 2010, the study used comparison group approach that considers crashes before and after the installation of cable barriers. Comparison segments were selected if they met criteria such as median width equal to the median width of the existing cable barrier segment plus or minus 10 feet, the segment length is equal to the cable barrier segment plus or minus 20 feet and the AADT is equal to that of the cable barrier segment plus or minus 1000 vpd. Using comparison group and screened median-related crashes only, CMF for fatal crashes was found to be 0.04, fatal and incapacitating injury 0.07, and 0.14 for fatal and all injury crashes combined.. These CMFs which translate into crash reduction percentages of 96% and 86% for fatal and fatal and all injuries combined respectively are comparable or slightly better compared to those obtained from other states. However, when all crashes within the cable segment were used (without screening median related), the CMF for fatal was found to be 0.46, and 1.18 for all crashes. This implies that installation of cable barriers in Tennessee significantly reduces fatal and severe injury crashes but increase minor PDO crashes (mainly those below $400). The developed CMFs responds to the intended benefits of the median cable barriers to prevent cross-median crashes which occurs when a vehicle leaves its travel way enters or crosses the median dividing the highway directional lanes and collides with vehicles in the opposite direction.

Study Citation:

Related Citations: Bryant, A., D. Chimba., and E. Ruhazwe. "Crash Modification Factors for Median Cable 1 Barriers in Tennessee." Presented at the 97th Annual Meeting of the Transportation Research Board, Paper No. 18-00225, Washington, D.C., (2018).

CMFs Associated With This Study

Category: Roadside

Countermeasure: Install cable median barrier

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.04 96 2 Stars Other K Not specified
0.09 91 2 Stars Other A Not specified
0.07 93 3 Stars Other K,A Not specified
0.15 85 3 Stars Other B Not specified
0.12 88 2 Stars Other A,B Not specified
0.14 86 2 Stars Other K,A,B,C Not specified
1.15 -15 2 Stars All All Not specified
0.46 54 2 Stars All K Not specified
0.94 6 2 Stars All K,A Not specified
1.11 -11 2 Stars All A Not specified
1.1 -10 2 Stars All B Not specified
1.18 -18 2 Stars All O Not specified
1.1 -10 2 Stars All A,B Not specified
1.07 -7 2 Stars All K,A,B,C Not specified
0.56 44 2 Stars Head on All Not specified
0.27 73 2 Stars Sideswipe All Not specified
0.5 50 2 Stars Head on,Sideswipe All Not specified