Date of this Version
Stolle, C.S., Sicking, D.L., Faller, R.K., and Reid, J.D. (2013). "Cable Median Barrier Failure Analysis and Remediation Phase II." Nebraska Department of Transportation Research Report TRP-03-319-13.
Cable median barrier crashes from a total of 12 states were analyzed. Crash data included scene diagrams, photographs, and field measurements, crash narratives, although the availability of data in each crash varied.
Major contributors to penetration crash propensity were identified: diving underride, in which the front end of the vehicle dropped below the bottom cable; prying, in which the vehicle profile caused cable separation or lifting; override; bouncing override, in which the vehicle rebounded after contact with the back slope and bounced over the top of the barrier; system failure, in which one component failure or design failure prevented the cables from adequately engaging the vehicle; and large vehicle crashes, such as tractor trailers, buses, and single-unit trucks into TL-3 systems.
Major contributors to rollover were identified: steep median slopes, in which the slope caused unstable bouncing or abrupt changes in slope profiles acted as trip points for the tires; broadside skid, in which the vehicle was skidding with a sideslip angle of nearly 90 degrees prior to contact with the barrier; contact with post, in which the post acted as a trip point; and other factors such as towing trailer units, median anomalies, or with large vehicles such as tractor-trailers, buses, or motor homes.
Recommended improvements to cable median barrier systems included: minimum top cable height of 35 in. (890 mm); maximum top cable height of 15 in. (381 mm); minimum of 4 cables supported by posts; higher lateral cable-to-post attachment strength at bottom and lower strength at top; low strong-axis strength post sections; and to eliminate cable entrapment in a vertical slot in the post when initial cable contact occurs at a post location.
A summary of factors and how they contributed to penetration, rollover, and severe crash probability is shown in Table 1.