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We have a situation where we want to place guardrail on a 1V:8H slope which extends a few feet behind the guardrail, before breaking off on a 1V:3H slope. Would a high tension cable guardrail such as Trinity's TL-3 system perform adequately in this situation? The standard system deflects up to around 9 feet (16 foot post spacing), so an impacting vehicle would be traversing the 1V:3H slope during redirection. I believe this deflection would not extend beyond the 1V:3H slope. Please see the attached drawing.

We looked over your installation and compared it with the testing we conducted with the MGS on 8:1 slope and our current cable testing. In that testing, we found that with a 5 ft offset, the MGS (with a 31 in. top rail height) just captured and contained the 2270P vehicle. We don't have similar cable testing on 8:1 slopes to compare with, but we know that the cable can redirect vehicles on the 4:1 slope as long as the vehicle is effectively captured. Based on this comparison we would recommend that the Trinity system be installed with the 2 ft offset rather than the larger 5 ft offset. The decreased offset should compensate for the cable heights of the Trinity system. In addition, offset should allow for capture of the vehicle and redirection even with the 1:3 slope behind the system. We believe that if the Trinity system captures the vehicle then the system will redirect the vehicle even if it intrudes on the 1:3 slope to some extent.