A guard rail (or guardrail, guide rail) is a roadside barrier designed to prevent vehicles from leaving the roadway at dangerous locations—steep embankments, bridge approaches, fixed objects, and opposing traffic. Guard rails are engineered to redirect errant vehicles back toward the road while minimizing impact forces on occupants. Types include W-beam (corrugated metal), cable barriers, and concrete barriers, each suited to different conditions. Guard rail placement involves trade-offs: barriers prevent severe run-off-road crashes but can cause injuries themselves if vehicles strike them at high speeds or wrong angles. Standards guide where guard rails should be installed based on hazard severity, traffic volume, and crash history. Municipalities maintain guard rails on local roads while provincial authorities handle provincial highways. Regular inspection ensures guard rails remain functional—damaged sections that haven't been properly repaired may fail during crashes.