What is the purpose of the 'Service Line' (Blue) in a combination vehicle?

It carries air, which is controlled by the foot brake or trailer hand brake.. Section 6.2: The service line (also called the control line

What is the purpose of the 'Service Line' (Blue) in a combination vehicle?

ANSWER BREAKDOWN
  • A. Incorrect. "It carries air to the trailer air tanks." is not correct. The service line (also called the control line or signal line) carries air which is controlled by the foot brake or the trailer hand brake.
  • B. Correct. The service line (also called the control line or signal line) carries air which is controlled by the foot brake or the trailer hand brake.
  • C. Incorrect. "It provides electricity." is not correct. The service line (also called the control line or signal line) carries air which is controlled by the foot brake or the trailer hand brake.
  • D. Incorrect. "It is for emergency braking." is not correct. The service line (also called the control line or signal line) carries air which is controlled by the foot brake or the trailer hand brake.