After coupling the trailer to the tractor, where should the tractor protection control valve be positioned?

The correct positioning of the tractor protection control valve after coupling the trailer to the tractor is in the normal position. When this valve is in the normal position, it ensures that the air supply is maintained to the trailer's air brake system, allowing the brakes to operate effectively. This is crucial for safely controlling the combination vehicle, as it ensures that the trailer's brakes are engaged whenever the tractor's brakes are applied.

Having the tractor protection control valve in the normal position allows for proper functionality of the braking system across both the tractor and the trailer. If the valve were closed or in maintenance mode, it would disrupt the air supply, leading to a potential failure of the trailer brakes when they are needed most. Additionally, placing the valve in the off position would further exacerbate this problem by completely severing air flow, preventing any braking capability for the trailer. Therefore, keeping the valve in the normal position is essential for safe operation and adherence to regulations governing the operation of combination vehicles.