When uncoupling a trailer, after shutting off the trailer air supply, what should be your next step?

When uncoupling a trailer, the correct next step after shutting off the trailer air supply is to back up gently to ease pressure on the fifth wheel locking jaw. This action is crucial because it helps to release any tension that may be present in the connection between the tractor and the trailer. By backing up slightly, the locking mechanism can disengage more easily, ensuring a smoother uncoupling process and preventing damage to the equipment.

The other steps may be important in the overall procedure of uncoupling, but they follow the initial action of relieving pressure. Beginning to lower the trailer landing gear before easing pressure could result in difficulties if the connection is still tight. Similarly, applying the tractor's parking brakes is essential, but it is typically done after ensuring that the trailer is safely detached. Disconnecting the electrical line should also occur after the fifth wheel has been properly disengaged to prevent shorts or other electrical issues. Focus on the sequence of actions ensures safety and efficiency during the uncoupling process.