2005 Commercial Driver’s License Manual Section 5 AIR BRAKES This Section Covers • Air Brake System Parts • Dual Air Brake Systems • Inspecting Air Brakes • Using Air Brakes This section tells you about air brakes. If you want to drive a truck or bus with air brakes, or pull a trailer with air brakes, you need to read this section. If you want to pull a trailer with air brakes, you also need to read Section 6, Combination Vehicles. Air brakes use compressed air to make the brakes work. Air brakes area good and safe way of stopping large and heavy vehicles, but the brakes must be well maintained and used properly. Air brakes are really three different braking systems service brake, parking brake, and emergency brake. The service brake system applies and releases the brakes when you use the brake pedal during normal driving. The parking brake system applies and releases the parking brakes when you use the parking brake control. The emergency brake system uses parts of the service and parking brake systems to stop the vehicle in a brake system failure. The parts of these systems are discussed in greater detail below.