How does pneumatic air braking operate to apply the service brakes on a heavy truck?

1. Compressed air generated by an engine-driven compressor is directed into brake chambers to push pushrods, slack adjusters, and expand brake shoes against drums
2. Vacuum suction pulls hydraulic fluid from the radiator into the wheels
3. Electrical electromagnets clamp directly onto the tyre rubber
4. Engine exhaust gas is injected into the tyre valves to stop rotation