A guard rail is a metal safety device that is placed along the edge of a roadway to prevent motorists from leaving the roadway. A guard rail typically either protects motorists from entering a steep slope, or it prevents collisions with objects like trees or bridge columns off the roadway. Avoiding crashes like these can save lives and prevent serious injuries. The guard rail absorbs the energy from the collision and redirects the vehicle back onto the road where it may come to a safe stop.

This is a typical guard rail application at the edge of a roadway shoulder:

Guard rail illustration

Illustration: Guard Rail

Guard rail photo

Photograph: Guard Rail

A. The guard rail absorbs the impact of a vehicle that leaves the roadway and protects the motorist from hitting an obstruction. The anchored rail absorbs the brunt of the blow and can redirect the vehicle.

B. The guard rail block out (made of wood or composite material) is typically 8 inches deep and is between the guard rail and post. The block out minimizes vehicle snagging on the posts and reduces the likelihood of a vehicle going over the guard rail by maintaining the height of the rail during the initial vehicle strike.

C. The guard rail post (which may be either steel or wood) provides the overall support and stability for the guard rail system. The posts are designed to dissipate the energy of the vehicle in the collision.