{{Unreferenced, date=September 2014
The driver's brake valve is a complicated valve system for controlling the
compressed air brake
A railway air brake is a railway brake power braking system with compressed air as the operating medium. Modern trains rely upon a fail-safe air brake system that is based upon a design patented by George Westinghouse on April 13, 1869. The ...
of a railway vehicle. Depending on its setting, it controls whether the brake pipes of a compressed air brake are evacuated and thus whether braking is applied or maintained; or if the brake pipes are connected to a compressed air reservoir, it controls whether the brakes are released again or remain released.
This equipment is found on the
footplate
A footplate provides the structure on which a locomotive driver and fireman stand in the cab to operate a British or continental European steam locomotive. It comprises a large metal plate that rests on top of the locomotive frame, usually it is ...
of locomotives or in the driver's cab of power cars and driving cars in multiple unit's, hence the name.
In the simplest case the position of the lever controls the extent to which the valve opens, how quickly compressed air can be released from the pipes or the reservoir in the braking system.
The setting of modern driver's brake valves controls the dynamic reduction of the remaining pressure in the brake pipes.