What is the function of the parking brake in an air brake system?

The primary function of the parking brake in an air brake system is to hold the vehicle stationary when it is not in motion. This is critical for preventing the vehicle from rolling, especially when parked on an incline or uneven surface. The parking brake operates independently of the service brakes used for stopping the vehicle while driving, allowing it to effectively secure the vehicle in place without reliance on the air brake system's main components.

In practical terms, when engaged, the parking brake typically uses spring tension to apply the brakes on the rear wheels (or all wheels, depending on the system), ensuring that the vehicle remains immobilized until the driver releases it. This function is vital for safety, particularly for vehicles carrying heavy loads, as it ensures that they do not unintentionally roll away.

Understanding the specific role of the parking brake helps drivers appreciate the importance of regular maintenance and operational checks, as the proper functioning of the parking brake system can prevent accidents and ensure compliance with safety regulations.