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 to reach Brentford and Hounslow. Taken together, this set of routes would be known as the “West London Orbital” railway. In March 2017 the West London Alliance group of local authorities commissioned a study to assess the feasibility of the line so that a decision could be taken as to whether it merited pursuing further. This study found that: In June 2017 Transport for London published the draft Mayor’s Transport Strategy, which stated that London government would work with the relevant boroughs to explore the feasibility of the proposed service, that would become the West London Orbital. In March 2018