When should the air lines be unhooked to uncouple a tractor from a semi-trailer?

Unhooking the air lines before separating the fifth wheel from the trailer pin is the correct approach when uncoupling a tractor from a semi-trailer. This sequence ensures that the air supply is disconnected prior to any physical separation, which helps prevent accidental release of the trailer or damage to the braking system. Disconnecting the air lines first allows any potential residual pressure to safely dissipate and ensures that the trailer's brakes are applied, which prevents movement during the uncoupling process.

By following this procedure, drivers safeguard themselves and others, as it helps maintain control over the trailer until it is fully disconnected. Proper training emphasizes the safety protocols to prevent accidents and ensure that both the tractor and trailer are prepared for disconnection in a controlled manner.