When should parking brakes be used in air brake vehicles?

Parking brakes should be used whenever the vehicle is unattended because they are specifically designed to hold the vehicle in place, preventing it from rolling away when the driver is not present. In air brake systems, the parking brake is critical for maintaining safety by ensuring that the vehicle remains stationary even on a slope or inclined surface. Engaging the parking brake when leaving the vehicle helps to protect against potential accidents or hazards that could arise if the vehicle were allowed to roll freely.

Using parking brakes when the vehicle is in motion, on level ground alone, or during high-speed travel is not appropriate. In those scenarios, the vehicle is actively being controlled by the driver, and the service brakes are engaged for stopping and controlling speed. Therefore, the proper use of parking brakes is key to the safety and stability of air brake vehicles, particularly when they are parked or left unattended.