When is it appropriate to use the hand valve to park a combination vehicle?

The use of the hand valve to park a combination vehicle is not considered safe practice under normal circumstances. The hand valve is designed primarily for use during emergency braking situations or to test the brake system and should not be relied upon as the primary means of securing the vehicle when parked.

Parking a combination vehicle requires the application of the service brakes, which are more reliable for holding the vehicle in place on any surface, whether flat or inclined. Using the hand valve to park can lead to a lapse in proper safety protocols and increases the risk of the vehicle rolling. For these reasons, it is emphasized that the hand valve should never be used for parking a combination vehicle.