Parking or emergency brakes of trucks and buses can be legally held on by

Parking or emergency brakes of trucks and buses can be legally held on by

• A. Hydraulic pressure
• B. Spring pressure
• C. Vacuum
• D. Electrical current

Answer: (B)

Heavy trucks and buses use spring-applied parking brakes. A strong coil spring inside the brake chamber automatically pushes the brake shoes against the drums when air pressure is released. Air pressure is what releases those springs to allow movement; as long as there’s enough air, the springs stay compressed and the brakes are released. If air pressure is lost, the springs engage and hold the brakes on, keeping the vehicle from moving. This design makes spring pressure the correct choice. Hydraulics, vacuums, or electrical current aren’t how the standard heavy-vehicle parking brake is held on.

Heavy trucks and buses use spring-applied parking brakes. A strong coil spring inside the brake chamber automatically pushes the brake shoes against the drums when air pressure is released. Air pressure is what releases those springs to allow movement; as long as there’s enough air, the springs stay compressed and the brakes are released. If air pressure is lost, the springs engage and hold the brakes on, keeping the vehicle from moving. This design makes spring pressure the correct choice. Hydraulics, vacuums, or electrical current aren’t how the standard heavy-vehicle parking brake is held on.