A crash barrier system for forming a crash barrier comprising a plurality of barrier units, each barrier unit comprising: a body having at least one crash wall, the body defining a cavity for receiving ballast; the crash wall comprising a series of longitudinal grooves on the outside surface thereof, each groove adapted to house a reinforcement bar; wherein a first barrier unit is connectable to an adjacent second barrier unit by locking pins; at least one locking pin able to pass through apertures in the body of the first barrier unit and reinforcement bar(s) housed in the crash wall of the first barrier unit, and through apertures in the adjacent second barrier unit and reinforcement bar(s) housed in the crash wall of the adjacent second barrier unit so as to lock the barrier units together to form the crash barrier.
