The automatic vacuum brake as described represented a considerable technical advance in train braking. In practice steam locomotives had two ejectors, a small ejector for running purposes (to maintain the partial vacuum at the correct level against inevitable slight air leaks in the train pipe and its connections) and a large ejector to release brake applications. The small ejector used much less steam than the large ejector but could not generate vacuum in the train pipe sufficiently quickly for operational purposes, especially in a long train. Later Great Western Railway practice was to use a vacuum pump instead of the small ejector – the pump was fitted to one of the engine crossheads and so did not use any steam, with the disadvantage that it only operated when the locomotive was in motion. The GWR favoured this due to the use of braking systems working on a vacuum level higher than other railways (see below) which would have required a relatively large and steam-hungry "small" ejector.