If supply pressure is rapidly lost, what function does the spring parking brake perform?

When supply pressure is rapidly lost, the spring parking brake performs the crucial function of automatically applying the brakes. This safety feature is designed to ensure that the vehicle remains stationary in the event of a loss of air pressure, which could occur due to a leak in the air system. The spring parking brake is preloaded with springs that are held in the released position by the air pressure in the system. Once that pressure drops below a certain threshold, the springs are allowed to engage, bringing the vehicle to a stop.

This mechanism is vital for safety, particularly in commercial vehicles that carry heavy loads. If the air supply is compromised, relying on the parking brake means that the vehicle cannot roll away unexpectedly, potentially preventing accidents and ensuring that it remains securely parked.