Crash barrier

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Standard guardrail (A-profile)

A crash barrier is a barrier on a road designed to prevent vehicles from leaving the roadway to improve road safety. Common sites for crash barriers are:

median separators on multi-lane highways
bridge supports
mountain roads

The design of the road barrier is generally such that a vehicle hitting the barrier is steered back onto the road. This may be achieved by designing the supports so that they break off on impact, allowing the barrier to deform and push the vehicle back on track. In some cases cost cutting has led to a failure of this mechanism, with so-called "duck-nesting" (after the shallow nature of a duck nest) of barrier support bases. When this happens the supports tilt over at the base instead of breaking off, allowing the barrier to collapse and the vehicle to go over the barrier. Motorcycles are very vulnerable to crash barriers. Large vehicles with a high centre of gravity, such as Sport utility vehicles, are also vulnerable to going over barriers on impact.

To prevent heavy vehicles going through or over the barrier and still maintain a low impact severity level, more stable systems like the German Super-Rail™ have been developed since the 1990s. It is tested to hold up and lead back trucks up to 40 tons while causing as low damage to smaller vehicles as the standard system of the 1930s.

Image:Super-Rail.jpg

Super-Rail™ Crash Barrier (left; on the right: standard spaced guardrail)

There is a variety of crash barriers: steel barriers are the prevalent sort but many environmental crash barriers and steel-wood guardrails have been introduced worldwide over the past few years.