The present invention provides a roadway barrier or guard rail system which has a post (12) which passes through the carriage (20) with the carriage (20) being free to move up along the post (12). The carriage (20) is prevented from moving down the post (12) by means of a stop or restraint (12.60,12.50,12.40,12.30) which is separate from and underneath the carriage (20) and which the carriage (20) abuts, with the stop or restraint (12.60,12.50,12.40,12.30) being located on the post (12). The carriage (20) is not otherwise restrained from moving up the post except by the curved channels through the carriage (20) which engage the extremities of the post, and the friction this may produce. Further systems are provided with the same features but additionally additional frictional or other forces such as shearing forces, produced by means of formations or fixtures to the post or the carriage which must be overcome after the carriage starts moving relative to the post, such as restraints or stops on the post above the carriage. In other embodiments additional frictional or shear forces must be overcome before movement between the carriage (20) and the post (12) will occur. The movement of the carriage (2) on the post (12) is guided by formations on the carriage (20) cooperating with the mating formations on the post (12).