The transport company A/S Akersbanen was founded by Aker Municipality on 7 June 1917. Next year the municipality applied the ministry to construct a light rail from Majorstuen to Sognsvann via Frøen with a branch line from Tåsen to Sagene. The transport company A/S Holmenkolbanen protested since they already had planned their own line to Sognsvann, but their complaint was rejected. The concession application was therefore approved and valid in 60 years from 12 July 1921.
The construction
The construction work started in January 1922, but was stopped two years later due to a labour conflict. It was resumed in 1932, and on 10 October 1934 the line opened and was also transferred to A/S Holmenkolbanen. The Sognsvann Line was constructed with double tracks to Korsvoll station (Østhorn) and with single tracks to the terminal station at Sognsvann. From 1937 to 1939 the part between Korsvoll and Sognsvann was reconstructed with double tracks.
Metro line
Nationaltheatret became the new terminal station in the city centre after a new tunnel was opened to Majorstuen on 27 June 1928. In 1977 the tunnel was extended to Sentrum station which became the terminus, but this was closed in 1983 due to leaks. The station was reopened on 8 March 1987 as Stortinget. In 1990 Oslo Municipality Council voted to upgrade the light rail to a metro line with a third rail. The construction work started the year after and the Songsvann Line reopened on 10 January 1993.
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