Arizona Air Brakes CDL Practice Test

If your truck or bus has dual parking control valves, what does it allow you to do?

1. Balance the service brake system

2. Release the spring brakes to move a short distance

3. Stay parked without using up service air pressure

4. Apply more brake pressure if the main tank is getting low

The correct answer is: Release the spring brakes to move a short distance

When a truck or bus is equipped with dual parking control valves, it allows the driver to release the spring brakes to move a short distance. This feature is especially useful in situations where the vehicle needs to reposition slightly or be moved for maintenance without the need for full air pressure in the system. By using the dual parking control valves, the driver can bypass the usual requirement for sufficient service air pressure, making it easier to maneuver the vehicle in tight situations or when servicing is needed. This capability enhances operational flexibility by providing a way to move the vehicle safely, especially when the air pressure in the service brakes may not be sufficient to fully engage the braking system. Overall, the dual parking control valves are specifically designed to assist in this manner, enabling controlled and safe movement of the vehicle even when the air pressure supplies are limited.