Although a guardrail is intended to protect the public, a number of safety concerns are associated with guardrails, particularly those crash barriers designed to work with automobiles. The first is the “end treatment,” or the finish on the end of the guardrail. Formerly, guardrails were not capped or finished in any way, leaving a wedge of sharp steel at either end of the stretch of guardrail. If someone collided with the end at a high rate of speed, the guardrail could potentially penetrate the car, causing injuries or death. Most modern end treatments are curved or flattened, and designed to resist the impact slightly.
If the guardrail or end treatment is too strong, it also has the potential of thrusting the car back into traffic. Therefore, most highway guardrails are designed to absorb energy, rather than deflecting it. In addition, traffic engineers have to think about the height of a guardrail. A tall vehicle may flip over a low guardrail, but a motorcycle could slide under a high one. Therefore, the height must be carefully considered before a guardrail is installed.
In order for a highway guardrail to be installed, traffic engineers must determine that there is a serious risk of severe off road collisions. In an area with a history of collisions, the risk is clearly illustrated, and the stretch of road will be added to the list of areas needing guardrails. In other situations, engineers have to evaluate the surroundings of the guardrail, looking for a cliff or other sharp change in elevation, and considering season conditions like ice and snow. If the risk is deemed serious enough, a guardrail will be installed.
