Abstract: A restraining barrier (30) is positionable across a roadway in a deployed position to define a restraining zone and may be moved vertically to a passive position by first and second transport members (13, 14) slideably mounted to first and second towers (3, 4) on either side of the roadway. The barrier may be a rectangular net. First and second cables (34, 35) each support an opposite end of the barrier to the said first and second transport means respectively and also couple the barrier to an energy absorber (known per se). The cable includes a support cable which also responds to the impact of a vehicle as by breaking. The cable is coupled to an operate indicator for producing a signal indicating the vehicle impact.