London Underground with smaller trains that run in two circular tunnels ("tubes") with a diameter about . These lines have the exclusive use of a pair of tracks, except for the Piccadilly line, which shares track with the District line between Acton Town and Hanger Lane Junction and with the Metropolitan line between Rayners Lane and Uxbridge; and the Bakerloo line, which shares track with London Overground services north of Queen's Park. Fifty-five per cent of the system runs on the surface. There are of cut-and-cover tunnel and of tube tunnel. Many of the central London underground stations on deep-level tube routes
West London Orbital Line, Bakerloo Line, High Speed 2, Crossrail and the Piccadilly Line. It is anticipated the line will be operational by the mid-2020s, reflecting the fact that it makes use of existing under-used rail infrastructure rather than requiring significant lengths of new track or tunnels to be built. An unrelated scheme of the same name was previously proposed in June 2008 by the West London Business group. That proposal involved the construction of a new underground line across West and South West London and did not progress beyond concept stage. The West London Orbital line consists of a number of distinct