Air Brake Practice Test

What occurs when the air pressure drops below a certain level in the air brake system?

1. Brakes automatically release

2. Warning light activates

3. Spring brakes engage

4. Emergency brakes are disabled

The correct answer is: Spring brakes engage

When the air pressure in an air brake system drops below a predetermined level, the spring brakes engage. This feature is crucial for safety because it ensures that in situations where the air pressure fails—such as a leak in the system or complete loss of pressure—the vehicle will come to a stop. The spring brakes are a fail-safe mechanism that utilizes strong springs to apply the brakes automatically, preventing the vehicle from rolling away and ensuring control over the vehicle. The activation of spring brakes under low air pressure serves as an essential safety measure, helping to prevent accidents that could occur due to brake failure. It's designed to protect both the driver and other road users by ensuring the vehicle cannot move if the air supply is compromised.