Purpose of Highway Guardrails

Obviously the size of the vehicle and the speed with which it hits the highway guardrail plays a part in how effective the guardrail is in slowing a vehicle.

Before guardrails are installed, engineers weigh all the potential factors to make sure that the placement works as well as possible in all conditions. The guardrail itself functions as an entire system rather than just stand-alone pieces. Each piece serves a different purpose as part of the whole. Everything from the posts that are driven into the ground to the way the guardrail connects to the post is important and plays a part.

The end terminal and the anchoring system at the end terminal is just as important. But overall, the highway guardrail basically consists of two key parts; the guardrail face and the end terminal.

The guardrail face is exactly what it sounds like; the part that extends from the terminal along the road. Its function is simple and always the same: to redirect a vehicle that runs into it back onto the roadway.

The end terminal is the starting and ending point of the guardrail and is also referred to as the end treatment. The end needs to be treated with some kind of energy absorbing treatment because the impact from a vehicle is absorbed and then slides down the rail. The end terminal functions in two ways; if a vehicle hits head-on the impact head slides down the guardrail redirecting it away from the vehicle until the energy from the impact has dissipated and the vehicle has come to a stop. When a car hits at an angle, the impact head may extrude the guardrail or gate out, allowing the vehicle to pass behind the guardrail. So in this instance the guardrail is pushed through, much like the action of a gate opening.