Final answer:
The tractor protection valve will close and the trailer emergency brakes will come on when there is a major leak in the service brake line. The tractor protection valve is a safety device in the air brake system of a tractor-trailer combination. It activates the trailer emergency brakes in the event of a loss of air pressure in the service brake line.
Step-by-step explanation:
The tractor protection valve will close and the trailer emergency brakes will come on when there is a major leak in the service brake line.
The tractor protection valve is a safety device in the air brake system of a tractor-trailer combination. It is designed to close and activate the trailer emergency brakes when there is a loss of air pressure in the service brake line, such as in the event of a major leak.
The service brake line is responsible for transmitting pressure from the brake pedal to the brake chambers, which apply the brakes. If there is a major leak in the service brake line, the tractor protection valve will close, cutting off the air supply and causing the trailer emergency brakes to come on.