What should you ensure before moving a tractor after pushing in the trailer supply valve?

Prior to moving a tractor after pushing in the trailer supply valve, it is essential to ensure that the air system is at normal pressure. This is crucial because the air system powers the brakes on both the tractor and the trailer. If the air system is not at normal pressure, the brakes might not function correctly, leading to potential safety hazards while moving the vehicle. It is vital for safe operation that the air pressure is at the appropriate levels; typically, this is around 120 psi for air brake systems.

Other factors, such as whether the trailer is loaded or the parking brake is released, may be important depending on the scenario, but the immediate requirement is to guarantee adequate air pressure. Without it, the braking system cannot be relied upon, compromising the safety of the vehicle's operation.