Barrier

The term barrier has a number of meanings in the context of road engineering and traffic management, amongst which are:

• A roadside or crash barrier, used to prevent traffic from leaving the road, and so protect adjoining property, or to segregate opposing flows on a dual carriageway – engineers usually refer to these as roadside or vehicle restraint systems to differentiate them from the other types of barrier.
• A parapet, used to protect traffic from a sharp drop, such as on a bridge
• A lifting barrier, used to control entry into, for example, a car park, or passage across a railway level crossing
• A height barrier, used to prevent high vehicles from entering a location, or to forewarn them of an overhead obstruction