The Service Air Line (usually Blue) is operated by:

The brake pedal and the trailer hand valve.. Section 6.2: The service line carries air controlled by the foot brake or the trailer hand

The Service Air Line (usually Blue) is operated by:

ANSWER BREAKDOWN
  • A. Correct. The service line carries air controlled by the foot brake or the trailer hand brake.
  • B. Incorrect. "A switch on the dash." is not correct. The service line carries air controlled by the foot brake or the trailer hand brake.
  • C. Incorrect. "The emergency line." is not correct. The service line carries air controlled by the foot brake or the trailer hand brake.
  • D. Incorrect. "The engine." is not correct. The service line carries air controlled by the foot brake or the trailer hand brake.