What is the primary advantage of a relay valve in a long air brake system, such as on a combination vehicle?

Question: What is the primary advantage of a relay valve in a long air brake system, such as on a combination vehicle?

Answer options: ✅ It speeds up the application and release of the service brakes.

• It stores additional air pressure for emergencies.
• It filters impurities from the air supply.
• It prevents air from freezing in cold weather.

Correct answer: It speeds up the application and release of the service brakes.

Explanation: Relay valves are used to shorten the time lag in applying and releasing brakes on long vehicles (like trailers), by supplying air directly from a local reservoir near the brake chambers, rather than from a distant control valve.