Answer :
Final answer:
After pushing in the trailer supply valve in a tractor-trailer, one must wait for the air system to be fully pressurized before moving the tractor to ensure the brakes function properly.
Explanation:
When the trailer supply valve is pushed in on a tractor-trailer air brake system, the air system must be fully pressurized before the tractor is moved. That means the air pressure should reach the manufacturer's specified level, ensuring that the brakes are properly engaged and disengaged. The trailer's brakes are governed by the trailer supply valve, also known as the tractor protection valve, which allows air to flow from the tractor to the trailer's brake system. It is crucial that the air system is pressurized correctly to avoid brake failure when starting to move the vehicle.
