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
Romford–Upminster line am and 8 pm on Sundays. The journey time from one terminus to the other is approximately nine minutes. During the construction of the railway in 1892, the geologist T. V. Holmes discovered a five-metre layer of boulder clay underlying the gravel and sand in a section just north of St. Andrew's Park. This is now the Hornchurch Cutting Site of Special Scientific Interest, which exhibits the southernmost limit of the Anglian ice sheet 450,000 years ago, the furthest south that any ice sheet reached. Romford–Upminster line The Romford–Upminster line is a railway branch line in Greater London that connects