Air Brake Practice Test 2025 – 400 Free Practice Questions to Pass the Exam

The use of spring pressure in parking or emergency brakes is fundamental to ensuring that a vehicle remains stationary when required. This system typically relies on a set of heavy springs that are compressed when the brake is applied. When the brake system is not actively engaged, such as when the driver releases the foot brake, these springs automatically extend, engaging the brake shoes against the brake drum or applying the brake pads against the rotor, thus securing the vehicle.

This design is particularly effective because it provides a fail-safe mechanism. In the event of a loss of air pressure due to a system failure, the springs will automatically engage the brakes, preventing the vehicle from rolling away. This makes spring pressure a reliable choice for emergency situations where other braking systems may fail.

Other types of pressure, such as air pressure and fluid pressure, are typically utilized for service brakes during regular operation rather than for parking or emergency situations. Vacuum pressure is also uncommon in modern braking systems. Therefore, spring pressure is specifically chosen for its ability to provide a strong and reliable means of holding the vehicle in place, especially in critical scenarios.