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 – every day, and the London Overground supports this type of travel. London Overground train service improvements are therefore needed to support new jobs and housing throughout inner London and parts of outer London.” The West London Alliance group of local authorities have agreed that the West London Orbital Scheme is to be a shared strategic infrastructure priority across borough boundaries, and that it will be incorporated in to all Local Plans. Discussions are currently underway between West London councils and London government on the future of the scheme. A number of independent analysis of the scheme have been undertaken,