Covers the requirements for and the performance of the braking devices of motor vehicles and their trailers (including semi-trailers) designed for use on the roads, that have a maximum design speed exceeding 25 km/h and that fall into any of the categories defined. Does not cover the braking devices of any vehicle propelled by electric power derived from batteries and that is pedestrian controlled, or any vehicle of mass not more than 230 kg specially designed and constructed, i.e. not merely adapted, for the use of any person suffering from some physical defect or disability and used solely by such person, or agricultural tractors and machinery, and any vehicle that runs on rails.