Supply or Emergency Line

The air lines in the trailer air brake system that charge the trailer air reservoir(s) and apply and release the parking or emergency brakes using the trailer push-pull valve in the tractor. Supply or emergency lines are commonly associated with the red air line function of the air system. 'Supply' is a post FMVSS 121 term and 'Emergency' is a pre-FMVSS 121 term.

Terminology Index