Kolsås Line

The Kolsås Line (Norwegian: Kolsåsbanen) is a 12.1-kilometer (7.5 mi) line of the Oslo Metro. It branches off from the Røa Line at Smestad Station and runs through western Oslo and Bærum to Kolsås Station. It serves the neighborhoods of Ullernåsen, Øraker, Jar, Bekkestua, Haslum, Gjettum and Kolsås. It is served by Line 3 of the metro at a 15-minute headway. The section from Jar to Bekkestua is built as a dual system with overhead wires, allowing Line 13 of the Oslo Tramway to continue from the Lilleaker Line to Bekkestua every ten minutes.

The Kolsås Line was built as an extension of the Lilleaker Line. It had been built to Lilleaker in 1919. The line was extended to Avløs on 1 July 1924, and the line was extended to Kolsås on 1 January 1930. The line was initially owned by Bærumsbanen, which was bought by Oslo Sporveier in 1934. A connection to the Røa Line opened on 15 June 1942, allowing the line access to the Common Tunnel. At this point the section from Sørbyhaugen to Kolsås was designated the Kolsås Line, while the section from Jar to Skøyen was retained as the Lilleaker Line. T1300 trains of the metro were introduced in 1982 and from 1995 it was linked with the eastern metro lines. The line was closed for upgrades to metro standard in 2006. It reopened in eight stages from 2008 to 2014. There are plans to extend the line to Rykkinn, Bærums Verk and Sandvika, although none of these have political priority.