Home › CDL Practice Tests › Air Brakes Questions › Question 105
If a trailer breaks away from the tractor on the road, what happens to the trailer's brakes?
- A.The loss of supply air applies the trailer spring (emergency) brakes and stops the trailer
- B.The trailer coasts freely until it runs out of momentum
- C.Only the trailer lights flash as a warning
- D.The trailer brakes release completely
Correct answer
A. The loss of supply air applies the trailer spring (emergency) brakes and stops the trailer
Why
Breakaway protection is built into the air design itself, not a separate cable. The instant supply pressure vanishes, the springs apply and bring the runaway trailer to a stop.
Manual topic: Air Brakes - Spring Brakes and Parking Brakes · From the Air Brakes practice bank (AB-105).