If your truck has a dual parking control valve, what does it allow you to do?

• A. Release the spring brakes to move a short distance using pressure from a separate tank.
• B. Lock the rear wheels when parked.
• C. Engage ABS on demand.
• D. Open the air tanks manually.

Answer: (A)

The main idea here is how parking brakes are released in air brake systems. On many heavy trucks, the parking brakes are held on by strong springs and are released by applying air pressure through a release valve. A dual parking control valve provides a separate air path from a dedicated reservoir to release those spring brakes, so you can move the vehicle a short distance to position it without using the main service-brake system. This lets you reposition or perform a quick brake check by using pressure from a separate tank rather than drawing from the normal braking air supply.