crash barrier 
noun British
A strong fence at the side of a road or in the middle of a dual carriageway or motorway, intended to reduce the risk of serious accidents.Should this mean that all roads should be made into dual-carriage-ways with central crash barriers?...
- His vehicle had, somehow, come off the motorway, missing the crash barriers, plunged down an embankment and through a wooden fence into the field he was now standing in.
- The car was trapped between the top of the lorry's cab and a crash barrier at the side of the road.