Circle line (London Underground) with the other London Underground sub-surface lines: the Hammersmith & City line from Hammersmith to just before Aldgate; the Metropolitan line from Baker Street to Aldgate; and the District line from Tower Hill station to Edgware Road station. The line is electrified with a four-rail DC system: a central conductor rail is energised at and a rail outside the running rail at , giving a potential difference of . The running rails are not electrified. Much of the double track railway from the Hammersmith terminus to Westbourne Park station is on a high brick viaduct. East of Westbourne Park the
West London line franchise as the London Overground concession, introducing new rolling stock and rebranding the West London line trains and stations in orange livery. The line appears today on the Tube Map as an orange stripe. New stations opened at in 2008 and in 2009, bringing main line rail services to a large catchment area in West London. In 1966 British Rail launched Motorail, a long-distance accompanied car train which transported passengers and their cars to the West of England and Scotland. The London Motorail terminal was at Kensington (Olympia), using the West London line for its wide connections to the UK