Air Brake Practice Test

What are the emergency and parking brakes usually held back by during normal operations?

1. Bolts/Clamps

2. Air pressure

3. Spring pressure

4. Weight of the vehicle

The correct answer is: Air pressure

During normal operations, emergency and parking brakes are typically held back by air pressure. In air brake systems, the brakes rely on air pressure to maintain disengagement, allowing the vehicle to move freely. When the vehicle is in operation, the air pressure in the system keeps the brakes released, preventing them from engaging unintentionally. In the event of a system failure or loss of air pressure, spring pressure activates the emergency and parking brakes to ensure that the vehicle comes to a halt safely. This mechanism serves as a vital safety feature, ensuring that if air pressure drops, the brakes will engage automatically, providing a fail-safe to prevent accidents. Other options such as bolts/clamps, spring pressure, and weight of the vehicle do not play a role in holding back the emergency and parking brakes during normal operations; instead, they have different functions within the braking system.