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Design and Evaluation of a Low-Tension Cable Median Barrier System

REPORT NUMBER

TRP-03-195-08

AUTHORS

Kirk Molacek, Karla Lechtenberg, Ronald Faller, John Rohde, Dean Sicking, Bob Bielenberg, John Reid, Cale Stolle, Erin Johnson, Cody Stolle

PUBLICATION DATE

2008-12-08

ABSTRACT

Prior full-scale crash testing and accident data analyses have both shown that low-tension, cable median barrier systems are one of the safest roadside barriers in existence. However, existing designs incorporate a relatively small spacing between cables which can allow some vehicles to underride the barrier and can limit the slopes upon which the barrier may be installed. Further, the most widely used design incorporates a wide post spacing of 4,877 mm (192 in.) which allows large lateral deflections. The new cable median barrier design reduces the issues by adding a fourth cable to reduce vehicle penetration over or under the barrier and decreasing the post spacing to reduce lateral deflections. The new cable median barrier designs were constructed and full-scale crash tested. The first cable median barrier, consisting of M203x9.7 (M8x6.5) posts spaced 1,829-mm (72-in.) on center, standard cable hooks, and woven cables, was impacted with an 820-kg (1,808-lb) small car. This cable median barrier design failed due to vehicle rollover. The redesigned cable median barrier, consisting of S76x8.5 (S3x5.7) posts spaced 2,438-mm (96-in.) on center, welded cable brackets, and non-woven cables, was impacted with an 820-kg (1,808-lb) small car. The vehicle was safely redirected. Following an analysis of the successful small car test, minor system design changes occurred to the cable median barrier system. These changes included lengthening the posts by 25 mm (1 in.) and adding cable retaining bolts at the top of the cable brackets. When impacted with a 2,000-kg (4,409-lb) pickup truck, the modified cable median system safely redirected the pickup truck. All three tests were conducted and reported in accordance with Test Level 3 of NCHRP Report No. 350.

KEYWORDS

Highway Safety, Roadside Appurtenances, Longitudinal Barriers, Cable Guardrail, Crash Test, Compliance Test

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