Home › CDL Practice Tests › Air Brakes Questions › Question 99
What are the two jobs of spring brakes?
- A.They cool the drums and charge the tanks
- B.They serve as both the parking brake and the emergency brake if service air is lost
- C.They steer the trailer and lock the doors
- D.They replace the need for service brakes
Correct answer
B. They serve as both the parking brake and the emergency brake if service air is lost
Why
One mechanism covers the parked vehicle and the worst-case air failure, which simplifies the system and its inspection. Drivers test both roles by setting the parking control and by watching automatic application in the pop-out test.
Manual topic: Air Brakes - Spring Brakes and Parking Brakes · From the Air Brakes practice bank (AB-099).