Emergency Air Line
Every combination vehicle has two air lines, the service line and the emergency line. They run between each vehicle (tractor to trailer, trailer to dolly, dolly to second trailer, etc.)
An emergency air line, also known as the supply line, is a crucial component of the air brake system in combination vehicles, such as semi-trailers. It supplies air to a trailer’s air tanks and controls the emergency trailer brakes.
Functions
The emergency line serves two primary functions:
- Supplies Air: Delivers compressed air from the tractor to the trailer’s air tanks, ensuring that there is sufficient air pressure for the braking system.
- Controls Emergency Brakes: Loss of air pressure in the emergency line causes the trailer emergency brakes to activate.
Identification
Emergency lines are often coded with the color red (red hose, red couplers, or other parts) to keep from getting them mixed up with the blue service line.