What is the primary function of the tractor protection valve in an air brake system?

The primary function of the tractor protection valve in an air brake system is to prevent loss of air to the trailer. This valve is a critical component that helps maintain the integrity of the air brake system by automatically closing if there is a sudden loss of air pressure in the tractor’s braking system. This action ensures that even if the tractor loses air pressure, the trailer's brakes remain applied, preventing potential accidents caused by trailer rollaways or loss of braking ability.

Maintaining air pressure is essential for the functionality of the entire braking system, but the primary role of the tractor protection valve specifically focuses on safeguarding the trailer from the loss of braking power due to air pressure issues in the tractor.