What are other terms for the Service Air Line?

The correct answer describes the Service Air Line as the Control line or Signal line. The Service Air Line is crucial in a combination vehicle system; it is responsible for controlling the braking systems of trailers and is linked to the air brake system. The terms "control line" and "signal line" suggest that this line plays a role in managing the operation or signaling of the braking system, which is essential for the safe and coordinated handling of trailer brakes in a vehicle combination.

Other terms related to air lines can refer to different functions; however, they do not accurately define the role of the Service Air Line. The Power line or Brake line primarily pertains to power delivery or actual brake functions rather than signaling or control. Auxiliary line or main line are terms that may describe other aspects of vehicle systems but do not align with the specific functions of the Service Air Line. Lastly, Safety line or reserve line would imply a backup function rather than the primary control aspect, which is not the purpose of the Service Air Line. Understanding these definitions helps in recognizing the critical components of a combination vehicle's braking system.