Cable median barrier failure analysis and remediation

On divided roadways, cross-median fatalities are disproportionately overrepresented in fatal and serious injury crashes. Many state DOTs sought to mitigate cross-median crash risk by installing cable median barriers. Despite increased crash rates, studies evaluating crash rates before and after cable median barriers were installed indicated excellent improvement in overall safety. Although cable median barriers are intended to prevent serious cross-median crashes, cable barriers can also contribute to serious injury and fatality crashes which would not have otherwise occurred, including penetration and rollover crashes. In order to reduce the frequency of undesirable penetration and rollover crashes occurring with cable median barriers in a cost-effective way, a research study was commissioned to study cable median barrier containment failures and methods of mitigating those failures. Barrier placement in the center of 40 ft (12 m) or wider V-ditches resulted in the highest penetration rate of 15%, but also resulted in the lowest rollover and severe crash rates of 2.3% and 1.8%, respectively. The 85th percentile trajectory angle associated with severe cable median barrier crashes was 39 degrees. The highest penetration and rollover rates were 16% and 13%, corresponding to large cars and SUVs, respectively. Generally, vehicles with low bumper heights, high CG heights, and higher masses were involved in statistically significantly more cable median barrier penetrations. Recommended changes to full-scale crash test requirements include substitution of large cars and SUVs for the small car and pickup trucks, as well as increasing the CG trajectory angle at impact to 39 degrees. Minimum and maximum cable heights should be 15 in. (381 mm) and 35 in. (889 mm), respectively, to reduce penetration frequency. Barriers should be installed as far from the travel way as practicable and preferably on slopes between 6:1 and 8:1. By implementing these improvements, many additional lives could be saved each year