Other forms: guardrails
A guardrail is a strong fence at the side of the road that can help protect drivers from serious injury. On a highway, center guardrails make it easier to avoid colliding with a car going the opposite direction.
Guardrails protect cars from hitting large roadside objects like trees and signs, or from hazards such as steep hills beside the highway. Additionally, guardrails are designed to keep cars upright, even when they strike the rail at fairly high speeds. In some places, low, protective fences around public spaces are also called guardrails — in this case, they're guarding against pedestrian injuries. "Stay back from the guardrail around the lion enclosure!"