What will likely happen if a driver crosses the air lines when hooking up to an old trailer?

When a driver crosses the air lines while hooking up to an old trailer, the most likely outcome is that the driver could drive away without trailer brakes. This situation occurs because the air lines are responsible for controlling the brakes on the trailer. If they are crossed, the signal that engages the brakes is not sent correctly to the trailer. As a result, the trailer’s braking system may not function as intended, which could lead to a situation where the driver is unaware that the trailer brakes are not engaged. This is particularly dangerous as it can cause a loss of control over the vehicle and trailer when in motion.

Understanding how air lines work is crucial for drivers operating combination vehicles. Properly connecting these lines ensures that both the truck and trailer function as a cohesive unit, especially for braking purposes.