New Jersey Air Brakes Practice Test

What is required to hold the parking or emergency brake on a heavy vehicle?

1. Hydraulic fluid

2. Air pressure

3. Spring pressure

4. Electric power

The correct answer is: Spring pressure

To hold the parking or emergency brake on a heavy vehicle, spring pressure is utilized as the mechanism of action. In air brake systems, the parking or emergency brake applies a mechanical force created by spring tension. When the brake is engaged, these springs are wound up and store energy, which is then released to apply the brake when needed. This design is crucial for safety, ensuring that the vehicle remains stationary even if air pressure, which is responsible for regular braking operations, is lost. Spring brakes automatically engage when air pressure drops below a certain threshold, preventing the vehicle from rolling. Understanding the operation of spring brakes is essential for safe vehicle handling, especially since they ensure that emergency situations can be addressed even in the event of system failures.