Ruislip depot is a London Underground traction maintenance depot on the Central line, and is situated between the stations of Ruislip Gardens and West Ruislip in the London Borough of Hillingdon. The depot is accessible from both ends, and was built for the Central Line extensions under the 1935-1940 New Works Programme. It was nearly completed by 1939, when the outbreak of the Second World War prevented further work. It was used as a factory for anti-aircraft guns during the war, and was finally opened in 1948. The main car shed has 16 tracks, and there is also a three-track car cleaning shed.
In 1969, a flash butt welding facility was constructed at the depot, to enable welded rails up to long to be produced. At a similar time, extra sidings were installed on land to the south of the original buildings, one of which provides a link to the Piccadilly Line and Metropolitan Line tracks to Uxbridge. Since Automatic Train Protection and Automatic Train Operation systems were installed on the Central Line, the depot has also hosted a unit of 1960 Stock which is privately owned by Cravens Heritage Trains.
Part of the depot was retrofitted with a green roof in 2012, as a trial for a larger-scale rollout across London Underground. The scheme was monitored by the University of East London.
History
Following its formation in 1933, the London Passenger Transport Board introduced a five-year New Works Programme, due to run from 1935 to 1940. A major part of this was extensions to the Central Line, both in the east, to Leytonstone, Woodford, Epping and Ongar, and in the west from North Acton Junction to Ruislip. The western extension would run along new tracks laid beside the Great Western Railway main line to . The extensions, which would create a route mileage of , meant that new depots would be required for the extra trains needed, and they were to be located at Hainualt and Ruislip. Work began, but none of the Central Line extensions were completed before the outbreak of the Second World War.
The Great Western Railway near Ruislip runs in a south-east to north-west direction, and the depot was to be built to the west of the existing railway and the new Central Line tracks. However, the land there was at a low level, and in order to raise it up, some of chalk infill was delivered by rail and spread over the area. The project saw widespread use of mechanical appliances, both in the spreading of the infill and in the excavation of trenches and foundations. A surface drainage system was installed over the whole site, and the chalk was covered with a layer of ash. The main car shed was designed with 16 tracks, each with an inspection pit, to facilitate maintenance of the trains. The pits were long, and had earthenware drains, which fed water into pipes, laid between adjacent tracks. The clay beneath the site contained sulphates, and consequently much of the drainage system, including some of and pipes, was constructed of spun-concrete sections, made with aluminous cement.
The depot was nearly finished by 1939, but with completion of the whole project delayed by the war, it was used as a factory, making anti-aircraft guns, and was also used to store spare and withdrawn rolling stock. Once hostilities had ended, work resumed on the western extension, much of which was constructed on bridges and viaducts, to carry it over a succession of roads, railways and canals. The work was carried out by the Great Western Railway, but after the nationalisation of the railways in 1948, responsibility for the line was gradually transferred to London Transport, a process that was finally completed in 1963. The depot, which opened in 1948, has connections to the running lines at both ends, and was initially designed for the stabling of 150 cars, but with provision for it to be extended to stable 350 cars. The main car shed is long, and 16 tracks enter it at the north-western end, where it is wide. Nine of the tracks are only covered for about half of its length, after which the building narrows, and the tracks funnel down into three, to enter the car cleaning shed, which is long and wide. A single-storey building with a flat roof, which is used for offices, stores and a repair shop, runs along the south-western wall of the main building. In the 1970s, there were some of tracks forming the approach lines, and another of track within the depot. The buildings are separated from the running lines by seven sidings, used for stabling trains in the open.