Traffic & Safety

Cable Barrier Report

High-tension cable median barrier (CMB) is a safety innovation in Kentucky, primarily used to prevent crossover crashes. In these crashes, a vehicle leaves the roadway on the left shoulder, crosses the median, and enters opposing lanes of traffic. The Kentucky Transportation Cabinet (KYTC) has observed inconsistent performance in CMB after a single vehicle hit; specifically, loss of tension in the cables. Ideally, if a second vehicle struck the cable barrier in a different location from the first hit, cable tension would be sufficient to prevent the second vehicle from crossing the median and causing a head-on collision.

KTC’ s objective during this cable barrier study was to improve the safety and effectiveness of the hundreds of miles of CMB installed across Kentucky. KYTC authorizes three cable barrier products for use, however, KYTC officials have questioned whether all products perform at a similar level. The KTC research team reviewed cable barrier best practices of other state DOTs, examined crash data, and performed on-site evaluations of CMB systems. They compared the three vendor CMB products used in Kentucky to look at performance differences and maintenance requirements. The most significant finding was that cable barrier has decreased incidents of crossover crashes in Kentucky, warranting the continued use of high-tension cable median barrier.

KTC researchers recommended several modifications to KYTC policy, specifications, and maintenance procedures. This will ensure Kentucky’s CMB systems meet all guidelines; most notably, correct post spacing and placement and adequate cable tension. Installing a concrete mow pad provides a better foundation for the posts, maintains cable tension, and allows for fewer repairs. KYTC district offices should implement a tension-inspection program for both annual inspections and after CMB repairs. Repair personnel should maintain a tension log that contains regular tension readings as well as readings made 72 hours after cable barrier repairs.

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