After the municipal merger between Aker and Oslo on 1 January 1948, the two municipal tram companies Akersbanerne and Oslo Sporveier merged; due to this the operation of all the four western lines were collected in A/S Holmenkolbanen. Operation was transferred to Oslo Sporveier on 1 August 1975, after it had bought almost all the shares in the company, and it had been delisted from the Oslo Stock Exchange. A/S Holmenkolbanen remained a separate company until 6 May 1992, when it was fully merged with Oslo Sporveier.