Which statement best describes the role of the spring brakes?

Which statement best describes the role of the spring brakes?

• A. They require hydraulic assistance to function
• B. They engage automatically when air pressure becomes too low to hold the vehicle
• C. They are used only on icy roads
• D. They replace the service brakes at all times

Answer: (B)

Spring brakes are a safety feature of air-brake systems that act automatically when air pressure drops. They are kept released by the air pressure during normal operation, but if the pressure falls below a safe level, the springs apply the brake, locking the wheels to hold the vehicle in place or stop it in an emergency. This automatic engagement whenever air pressure is too low to hold the vehicle is exactly how the system provides a parking/emergency brake. They don’t rely on hydraulic assistance, they aren’t used only on icy roads, and they don’t replace the service brakes during normal driving.

Spring brakes are a safety feature of air-brake systems that act automatically when air pressure drops. They are kept released by the air pressure during normal operation, but if the pressure falls below a safe level, the springs apply the brake, locking the wheels to hold the vehicle in place or stop it in an emergency. This automatic engagement whenever air pressure is too low to hold the vehicle is exactly how the system provides a parking/emergency brake. They don’t rely on hydraulic assistance, they aren’t used only on icy roads, and they don’t replace the service brakes during normal driving.