What is the main function of the governor in an air brake system?

Answer: B — To control the maximum air pressure in the braking system

In an air brake system, the main function of the governor is to control the maximum air pressure in the braking system. The governor regulates the compressor's operation to maintain a specific range of air pressure necessary for effective braking performance. It ensures that the air tanks are filled to an adequate pressure while preventing over-pressurization, which could lead to safety hazards such as brake failure or leaks. By monitoring the air pressure and activating the compressor when it drops below a certain level, the governor helps maintain optimal performance of the brakes. If the pressure exceeds the preset limit, the governor will prevent additional air from entering the system, ensuring that the brakes function properly and safely.