 To save the company, the municipal owned Akersbanerne agreed to a merger between A/S Holmenkolbanen and two of Akersbanerne's three lines—the Smestad Line and the under construction Sognsvann Line that would both share the tunnel into the center, with the transaction taking place on 16 November 1933.In 1942 the Kolsås Line was rebuilt to terminate through the Smestad Line, and in 1944 the owner Bærumsbanen was bought by Oslo Sporveier.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.