Evaluation of Wisconsin Median Cable Barrier Systems

Granting Agency: Wisconsin Department of Transportation

Researchers: Xiao Qin, Fenghuan Wang, Andrea Bill, Madhav Chitturi, David Noyce

A cross median crash (CMC) is a typically violent collision with a disproportionately high probability of fatalities and severe injuries. To mitigate the devastating effects of CMCs, the Wisconsin Department of Transportation (WisDOT) installed median cable barriers at several locations on state highway sections where a number of CMCs have occurred. This study evaluated the safety effectiveness and performance of four different cable barrier systems used as a CMC countermeasure, namely CASS, Brifen, and Gibraltar, all considered high-tension cable barriers, and a common low-tension cable barrier system.

Phase II of the study built upon the original study and evaluated 10 high-tension systems at 16 study sites. At least one system produced by each of the five predominant cable barrier manufacturers was evaluated.

For this study, cable barrier systems were evaluated in terms of safety and maintenance performance; a benefit-cost (B/C) analysis was also performed. Systems were evaluated via the simple before-after methodology in which crash frequencies and rates were compared in periods prior to and following barrier installation. Additionally, binary logistic regression analysis was used to compare barriers in terms of containment performance, breach likelihood, and crash severity associated with barrier hits. The analysis showed that differences between systems were often negligible. The Gibraltar TL-3, 3-str barrier, however, was shown to significantly increase the odds of a vehicle being stopped upon hitting the barrier.

In conclusion, the cost per hit and unit cable operations and maintenance cost per mile generated from Wisconsin data can assist WisDOT in planning future cable barrier installations and developing predictive cable median barrier warrants.