Home › CDL Practice Tests › Air Brakes Questions › Question 3
In a dual air brake system, what does the secondary system typically control?
- A.Only the rear drive axle brakes
- B.The service brakes on the front steering axle
- C.Only the spring brakes on the trailer
- D.The engine retarder and exhaust brake
Correct answer
B. The service brakes on the front steering axle
Why
The secondary circuit normally supplies the front axle service brakes and shares supply duties with the primary circuit. If the primary fails, the secondary still gives the driver front-axle braking and a way to stop.
Manual topic: Air Brakes - Dual Air Brake Systems · From the Air Brakes practice bank (AB-003).