What would cause air brakes that have been applied to "creep off" most quickly?

The rapid "creep off" of air brakes is primarily influenced by a leak in the brake cylinder. When the brake cylinder has a leak, it allows air pressure to escape more quickly than it can be replenished from the equalizing reservoir. This loss of pressure reduces the force exerted by the brake, causing the brakes to release or "creep off." The brake cylinder is directly responsible for the application and release of the brakes, so any leak in this area directly impacts how quickly the brakes can no longer hold the train in place.

In contrast, a leak in the equalizing reservoir, while it would affect the overall pressure available to the brake system, does not necessarily lead to a rapid release of the applied brakes since the reservoir functions differently compared to the brake cylinder. A brake pipe failure could lead to air loss, but it typically affects the entire system rather than just causing brakes to creep off. A controller malfunction may result in improper brake operation but doesn’t inherently speed up the release of brakes already applied. Thus, the brake cylinder leak is the most direct and rapid cause of air brakes "creeping off."