bought twelve Class A trams and twelve trailers from Zypen & Charlier of Germany. After running along the Bærum Line to Skøyen, the trams continued along the Oslo Sporveier-owned Skøyen Line to Athenæum in the center of Oslo. Each station was equipped with a small building where there was a kiosk, telephone, ticket sale and freight handling. The depot was originally planned to be situated at Haslum, but a more suitable lot was found at Avløs. A subdivision with dwellings for 39 employee families was also built there. On 27 August, the ground around Bekkestua started to sink; the track was lifted and covered with stone. Two days later, the track had sunk into the ground and a small island was created in a nearby lake. It turned out that the area was resting on clay that had transformed to quick clay after a water pipe had broken. It took two weeks to repair the damage. It became clear in 1924 that Bærumsbanen would also have to operate city services along the Skøyen Line in Oslo. This caused the company to order three trams and trailers, this time from Skabo Jernbanevognfabrikk. At the time it cost NOK 0.15 to take the tram within the city limits of Oslo, and NOK 1 from the city to Bekkestua. Passengers carried out a strike in 1924; this resulted is slightly cheaper tickets, but at the same time the trams and stations were equipped with advertisements. Kolsås extension The initial plans called for an expansion from Haslum to Kolsås. It was originally planned to run past Bærum Hospital to Løken Farm, but lack of funding instead forced the company to build the line along a cheaper section about one kilometer (half a mile) from the hospital. The free land for the extension was only valid for a limited time, and to be able to construct the line before the deadline, a single-track solution was chosen. The plans were passed by the municipal council in 1927 and concession granted on 10 February 1928. Construction started immediately, followed by track laying commencing in June 1929. The extension opened on 1 January 1930. Valler Station had a passing loop and at Kolsås a balloon loop was built. The line caused the closing of the bus from Haslum to Bærum Hospital, and the bus from Lommedalen was rerouted to correspond with the tram at Kolsås. A mixed route