A heavy goods vehicle (HGV) braking system typically consists of air brakes, which use compressed air to apply the brakes, as well as a mechanical or hydraulic system as backup. The air brake system is made up of an air compressor, air dryer, air tanks, and brake chamber. The compressor compresses the air and sends it to the dryer, which removes moisture and impurities before it is stored in the tanks. When the driver presses the brake pedal, air is released from the tanks and sent to the brake chambers, which then push the brake shoes or pads against the wheels, slowing the vehicle. The mechanical or hydraulic system acts as a fail-safe in case of air pressure loss in the air brake system.