CDL Vehicle Combination Practice Test

During coupling inspection, what is an important check for the air lines?

1. They should be completely taut

2. There should be a little slack in the air lines

3. They must be visible from the driver's seat

4. They should show no signs of damage

The correct answer is: There should be a little slack in the air lines

During coupling inspection, it is essential for the air lines to have a little slack. This slack is critical because it prevents the air lines from being overly taut, which can create tension during vehicle movement and coupling/uncoupling processes. If the air lines are too tight, they can risk being damaged or disconnected when the vehicle goes over bumps, turns, or experiences changes in load. Having a little slack ensures that the air lines can flex and move without putting stress on the connections, maintaining functionality while preventing potential failures. In contrast, if the air lines were completely taut, it could lead to wear and could result in air leaks or disconnection, ultimately impacting the braking and operational system of the combination vehicle.