In moderate to severe impacts heavy vehicles tend to roll over existing post and rail safety fences. This tendency can be offset by introducing a fracture point at the base of each intermediate post. A steel safety fence designed on this basis has been developed, the frangible base being symmetrical so that it can be used on the central reserve as well as at the road edge. Essentially the fence consists of a three-ridge guardrail 508 mm in depth firmly bolted to strong steel tubular posts at 2 m intervals. Each post is held at its base by a steel pin which passes through the post, and two vertical support lugs firmly secured to a concrete anchorage. Upon impact the steel pin breaks to release the post which remains attached to the guardrail. Development tests are described which have enabled the strengths of the component parts of the frangible posts to be determined, to provide a containment capability better than that of existing safety fences. (Author/publisher)
Abstract