Enhancements

Electro-pneumatic or EP brakes are a type of air brake that allows for immediate application of brakes throughout the train instead of the sequential application. EP brakes have been in use in German high-speed trains (most notably the ICE) since the late 1980s, and in British practice since 1949, fully described in Electro-pneumatic brake system on British railway trains. Electro-pneumatic brakes are currently in testing in North America and South Africa in captive service ore and coal trains.

Passenger trains have had for a long time a 3-wire version of the Electro-pneumatic brake, which gives seven levels of braking force. In most cases the system is not fail-safe, with the wires being energized in sequence to apply the brakes, but the conventional automatic air brake is also provided to act as a fail safe, and in most cases can be used independently in the event of a failure of the EP brakes.

In North America, WABCO supplied HSC (High Speed Control) brake equipment for several post-World War II streamlined passenger trains. This was an electrically controlled overlay on conventional D-22 passenger and 24-RL locomotive brake equipment. On the conventional side, the control valve set a reference pressure in a volume, which set brake cylinder pressure via a relay valve. On the electric side, pressure from a second straight-air trainline controlled the relay valve via a two-way check valve. This "straight air" trainline was charged (from reservoirs on each car) and released by magnet valves on each car, controlled electrically by a 3 wire trainline, in turn controlled by an "electro-pneumatic master controller" in the controlling locomotive. This controller compared the pressure in the straight air trainline with that supplied by a self lapping portion of the engineers valve, signaling all of the "apply" or "release" magnets valves in the train to open simultaneously, changing the pressure in the "straight air" trainline much more rapidly and evenly than possible by simply supplying air directly from the locomotive. The relay valve was equipped with four diaphragms, magnet valves, electric control equipment, and an axle-mounted speed sensor, so that at speeds over 60 mph full braking force was applied, and reduced in steps at 60, 40 and 20 mph, bringing the train to a gentle stop. Each axle was also equipped with anti-lock brake equipment. The combination minimized braking distances, allowing more full-speed running between stops. The "straight air" (electro-pneumatic trainline), anti-lock, and speed graduating portions of the system were not dependent on each other in any way, and any or all of these options could be supplied separately.

Later systems replace the automatic air brake with an electrical wire (in the UK, at least, known as a "round the train wire") that has to be kept energized to keep the brakes off.

More recent innovations are electronically controlled pneumatic brakes where the brakes of all the wagons (cars) and locomotives are connected by a kind of local area network, which allows individual control of the brakes on each wagon, and the reporting back of performance of each wagon's brakes.