Evaluation Of Safety Effectiveness Of Median Cable Barriers Installed On Freeways In Ohio

The Ohio Department of Transportation (ODOT) began installing median cable barriers in 2003 along highway medians for all roadways that were narrower than 59 ft. The central goal of this work was to prevent cross-median crashes (CMCs) that raised a concern due to their frequencies and severe injuries they caused when they occurred. Cross-median crashes occur when a vehicle leaves its travel way, enters or crosses the dividing median, and collides with vehicles moving in the opposite direction. This study received data from 41 locations totaling about 201 miles of installed median cable barriers in the years 2009-2014. These locations experienced 2,498 median related crashes before and after installation. The study involved a review of police reports to identify target crashes and the manner in which the vehicles hit or crossed the cable barriers, either by penetrating the cables, over-riding, under-riding, stopped, or redirected. A detailed analysis of cable hits was also conducted. The study found that median cable barriers were effective in stopping vehicles from breaching the barrier; 95.4 percent of all cable median barrier crashes had no penetration of the cable barrier, i.e., the vehicles where stopped or bounced by the cables. This thesis study summarizes some key findings of safety effectiveness evaluation of the median cable barriers in Ohio. The findings of overall statewide crash reduction after the median cable barriers compared to before period are based on the safety effectiveness percentages computed by Empirical Bayes (EB) before-after study method using the Highway Safety Manual's (HSM) procedures. Safety effectiveness of Ohio's statewide cable barriers was found to be 73.9 percent for total crashes, 80.4 percent for fatal and injury (FI) crashes combined and 80.1 percent for fatal, incapacitating, and non-incapacitating injury (KAB) crashes combined. Therefore, the estimated crash modification factors (CMFs) for median cable barriers installed in Ohio's Interstate system for total, FI, and KAB crashes are 0.261, 0.196, and 0.199, respectively. Overall, the evaluation results show that the median cable barriers installed in Ohio's Interstate system are effective in reducing cross-median severe injury crashes, which was the main objective of ODOT's installing median barriers in their Interstate highway system.