If your truck or bus has dual parking control valves, you can use pressure from a separate tank to:

When a truck or bus is equipped with dual parking control valves, this feature allows the driver to use pressure from a separate air tank specifically to release the spring emergency and parking brakes. This capability is crucial for situations where the vehicle must be moved short distances, such as when it is parked in a way that obstructs traffic or needs repositioning.

The dual parking control system provides an important safety measure, allowing movement without fully engaging the service brakes, which are used for regular braking while in motion. By utilizing the pressure from a separate tank, drivers can safely disengage the parking brakes momentarily, ensuring they have enough control and can maneuver the vehicle, even when the air pressure in the primary system is low.