Cody S. Stolle
Date of this Version
Dowler, N.T., Stolle, C.S., In-Service Performance Evaluation and Installation Recommendations for Cable Median Barriers on Non-Continuously Shielded, Divided-Median Kansas Freeways, Midwest Roadside Safety Facility, University of Nebraska-Lincoln, Lincoln, NE, April 2021.
The Kansas Department of Transportation (KDOT) installed 7.95 miles of cable median barrier (CMB) along K-10, K-96, and US-75 freeways in 2011 and 2012. In January 2020, KDOT funded a study to determine the in-service performance of its CMBs. In addition, KDOT sought to determine if it was cost-effective to modify guidelines for installing median barriers, which were based on annual daily traffic and median width.
Researchers reviewed every crash within approximately ¼ mile of a CMB installation and extracted crashes which involved a CMB impact. Researchers analyzed the critical details of each CMB crash, with particular emphasis on penetrations, in which a vehicle passed from the impact side to the opposite side of the barrier. In two penetration crashes, the vehicle completely traversed the median and encroached into the opposing lanes (CME), and one impacted an oncoming vehicle (CMC). Although the dataset was small, penetration and rollover rates were lower than other state DOT averages. Overall, the performance of the KDOT CMB was deemed acceptable and comparable to other states.
Researchers investigated the cost-effectiveness of installing CMBs based on the frequency of critical crash events. A detailed examination of 16,721 crashes on non-continuously shielded, divided-median Kansas freeways from 2014 to 2018 was undertaken, which focused on median departures, crashes which reached the median centerline, CMEs, and CMCs. Benefit-to-cost ratios were calculated for various median widths, roadways, and traffic volume conditions. Previous median barrier warrant guidelines were determined to still be cost-effective and changes to KDOT policy were not recommended.
A review of all off-road crashes which did not enter the median was conducted to examine any trends or characteristics between contributing factors or fixed objects struck. The relationship between crash cause and traffic volume was explored, identifying the traffic volume range at which each contributing factor was most prevalent. A disproportionate number of severe crashes following contact with bridge piers was observed, and recommendations were made for further analysis.
Advisor: Cody S. Stolle