page_title: Common Tunnel
section_title: Route
hierarchical_section_title: Common Tunnel / Route
context_page_description: The Common Tunnel, sometimes called the Common Line, is a 7.3-kilometer long tunnel of the Oslo Metro which runs through the city center of Oslo, Norway. The name derives from the fact that all six lines of the metro use the tunnel, which runs from Majorstuen to Tøyen. The section has six stations, including the four busiest on the metro.
  The tunnel was first built as two separate tunnels which were later connected. The Holmenkolbanen company opened the western section of the tunnel from Majorstuen via Valkyrie plass to Nationaltheatret in 1928. In 1966, the Oslo Metro opened, including the tunnel from Tøyen via Grønland to Jernbanetorget. In 1977, the eastern end was extended to Sentrum, but the extension was closed in 1983 because of water leakages. In 1987, the Sentrum station reopened as Stortinget, and became the terminus of both the western and eastern lines. By 1993, the western end had been upgraded to metro standard, Valkyrie plass was closed, and the first trains ran through the whole tunnel.
  The section from Tøyen to Brynseng, although not completely located within the tunnel, is considered part of the Common Line.
context_section_description: The Common Tunnel is a 7.3-kilometer (4.5 mi)  long double track rapid transit line running east from Majorstuen to Tøyen and onwards to Brynseng. The section from Tøyen to Brynseng is partially above ground and is only sometimes considered part of the tunnel and the Common Line. At Tøyen, the Grorud Line branches and continues past Carl Berners plass as part of the same tunnel. From Carl Berners plass to Ensjø, there is a single-track branch, which allows trains access to the other eastern lines without having to change direction. Three stations serve the city center: Nationaltheatret, Stortinget and Jernbanetorget, while Majorstuen, Tøyen and Grønland serve mixed residential and commercial areas.
caption: Schematic of the metro network, showing that all lines run through the Common Tunnel.