On 1 October 1944, Oslo Sporveier bought Bærumsbanen and took over the operation of the Lillaker-, Ekeberg- and Østensjø Line. The municipalities of Oslo and Aker were merged 1 January 1948, and Aker's municipal tram company Akersbanerne was merged into Oslo Sporveier. This company did not operate any lines, instead it had a majority ownership in Holmenkolbanen that operated the four suburban lines in Western Oslo: the Holmenkoll Line, Sognsvann Line, Kolsås Line and Røa Line. The companies preferred shares were however still listed on the Oslo Stock Exchange.