View Q&A

I think Missouri requested an informed opinion on how to place high tension

cable guardrail in the median.

When to terminate it prior to bullnoses, or tied in behind W-beam End Treatments?

Do any of the high tension cables allow placement on slopes greater than 10:1?

1. When to terminate it prior to bullnoses, or tied in behind W-beam End Treatments?

I reviewed the full-scale crash tests for the major high tension cable systems. All of the reviewed systems had dynamic deflections between 6.5 and 8.9 ft when impacted with the 2000P vehicle under TL-3 impact conditions. Keeping in mind that these tests where conducted on relatively short installations, we can expect slightly higher levels of dynamic deflection in longer installations. As such we would recommend at least a 10-ft lateral offset between the high tension cable barrier systems and the bullnose. In addition, we would recommend termination of the high tension cable barrier at least 31' downstream of the first post of the bullnose. This distance should be sufficient to allow the bullnose to provide redirection of a vehicle if it impacts near the cable end terminal and gates through the terminal. See the attached pdf file for a schematic. Another alternative might be to not use a bullnose at all, but rather an end terminal appropriate for median use with a similar offset for the cable.

As far as tying the high tension cable behind W-beam end terminals, we cannot give much guidance. We have successfully tested two low-tension cable guardrail to W-beam end terminal end treatments in the past. These are the FLEAT cable transition and the South Dakota cable transition. However, we cannot predict how these designs will perform when used with high-tension cable barrier systems and thus cannot recommend their use. We would recommend that you contact the individual high tension system manufactures for their recommendations.

2. Do any of the high tension cables allow placement on slopes greater than 10:1?

Based on our current knowledge, none of the high-tension cable guardrail systems have been tested on a slope at this time. As such, we would be forced to recommend that they be used on slopes of 10:1 or less for the time being. We do believe that the cable barrier manufactures are starting to attempt to address this issue. Again we would recommend that you contact them in order to get the most up to date information on their system for applications on slopes. We would be interested to see what they have to say.