This SAE Recommended Practice presents performance requirements for the brake systems of motor vehicles intended for roadway use and falling into the following classifications: Light trucks and buses: 6001-10 000 lb (2700-4500 kg) gvw; Truck and bus: Over 10 000 lb (4500 kg) gvw; combination of vehicles towing vehicles over 10 000 lb (4500 kg) gvw. Acceptable performance requirements are based on data obtained from applicable sections of SAE J786a (March, 1978). The purpose of this recommended practice is to establish the minimum brake system performance requirements with regard to: 3.1 Stopping ability--of cold brakes, as affected by vehicle speed. 3.2 Stopping ability--of hot brakes, as affected by vehicle speed and duty cycle. 3.3 Pedal force (air pressure) requirements--maximum allowable. 3.4 Brake stability. 3.5 stopping ability and recovery of wet brakes. 3.6 Stopping ability of emergency brake system. 3.7 Brake effectiveness distribution for vehicles in combination.