A crash bar is a mechanism for unlatching a door, consisting of a metal bar fixed horizontally to the front of the door and hinged. It is operated by pushing on it, which unlatches and opens the door. Many countries' building codes require them on all fire and emergency exits. They are so named because they can be operated by someone "crashing" into them; the alternate term "panic bar" implies a similar meaning.
Crash bars also refers to motorcycle engine guards. They are commonly made of tubular steel bent into a "U" shape and mounted to the sides of a motorcycle's lower frame. They primarily protect the bike's engine and body panels during slides or tipovers but also serve as a mount point for accessories like highway pegs, lights and, on police motorcycles, sirens, cameras and radar guns.