New Jersey Air Brakes Practice Test

What type of pressure legally holds parking or emergency brakes on trucks and buses?

1. Air pressure

2. Fluid pressure

3. Spring pressure

4. Hydraulic pressure

The correct answer is: Spring pressure

The correct answer is that spring pressure legally holds parking or emergency brakes on trucks and buses. Spring brake systems are designed to engage automatically when air pressure is released, making them a reliable method for ensuring that the vehicle remains stationary when parked or in an emergency situation. In a typical air brake system, the parking brakes are controlled by a set of powerful springs that are held in a compressed position by air pressure while the vehicle is in operation. When the driver releases the air pressure from the system (either deliberately or due to a failure), the springs decompress and engage the brakes, preventing the vehicle from rolling away. This design enhances safety, as it provides a fail-safe mechanism that automatically activates the brakes if there is a loss of air pressure, ensuring that the vehicle does not move unexpectedly. Understanding this mechanism is essential for vehicle operators and maintainers since it highlights the importance of maintaining proper air pressure levels and the functionality of the air brake system to guarantee safe operations.