Crash Modification Factors for High-Tension Cable Median Barriers: An Empirical Bayes Before

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Crash Modification Factors for High-Tension Cable Median Barriers: An Empirical Bayes Before–After Study

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Gayah, Vikash V. / Donnell, Eric T. / Liu, Hao / Prajapati, Abhishek

Cross-median crashes involve vehicles departing the roadway to the left, crossing the median of a divided highway, and colliding with a vehicle traveling in the opposite direction. These crashes are severe, often resulting in fatal or serious injuries. To mitigate this crash type, transportation agencies may install median barriers. The high-tension cable median barrier is a flexible system that is intended to contain or redirect vehicles entering the median—this barrier type has recently been installed along freeway segments throughout Pennsylvania. The purpose of this study is to develop crash modification factors for this barrier system. An empirical Bayes observational before–after study was used to develop the crash modification factors—various crash types, area types (urban versus rural), and barrier placement locations were considered. The results indicate that, when considering both urban and rural locations combined, the installation of high-tension cable median barriers is associated with an increase in total, fatal plus injury, property-damage only, and hit-barrier crashes on freeway segments. The expected number of cross-median, fatal plus suspected serious injury, and fatal plus suspected serious injury cross-median crashes is expected to decrease when installing high-tension cable median barriers. The crash modification factor for high-tension cable median barriers is higher for installations along the shoulder of the freeway segment when compared to installations in the center of the median.