DD3 brake release

[Lin]

There is a schrader valve in the compartment below the driver's seat of my MC5a.  I had assumed it was for airing up the bus.  I hook into it yesterday and found that it did not air the bus nor even fill the air bags.  I stepped on the brake pedal and there was no musical "whoosh".  I than released the DD3 park brake and the bus rolled.  Is this valve there to be able to move the bus if disabled?

[JackConrad]

Yes, this can be connected to a wreckers air supply when towing to prevent DD3s from locking the rear wheels.  Jack