In an air brake system, the service brake provides what function?

• A. It applies and releases brakes when the pedal is pressed
• B. It stores energy
• C. It activates the parking brake
• D. It uses vacuum for braking

Answer: (A)

The service brake is the part of an air brake system that responds to the driver’s brake pedal to control braking. When you press the pedal, compressed air from the reservoirs is directed to the brake chambers at each wheel, and that air pressure moves the actuators to push the brake linings against the drums or discs, producing friction to slow or stop the vehicle. Releasing the pedal relaxes the air pressure, allowing the brakes to release and the vehicle to roll freely again. This system uses compressed air, not vacuum, and it’s separate from the parking brake, which is designed to hold the brakes on when the vehicle is parked. So the service brake’s function is to apply and release the brakes when the pedal is pressed.