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 West London Orbital The West London Orbital is a proposed extension to the London Overground that makes use of a combination of existing freight and passenger lines including the Dudding Hill Line, North London Line, and the Hounslow Loop. The route runs for approximately 11 miles from West Hampstead and Hendon at the northern end to Hounslow at the Western end via Brent Cross West, Neasden, Harlesden, Old Oak Common, Acton and Brentford. The route would improve rail connectivity across West and North London, and establish a number of new connections to existing radial rail infrastructure including Thameslink, the Jubilee