Services on the Østensjø Line were carried out by Line 3, originally running from Skullerud to Jernbanetorget in the city center. The fourth line of the metro was the Furuset Line. Its initial opening took place on 18 November 1970, when services with Line 6 commenced to Haugerud. The city center service was extended to Sentrum on 9 January 1977. However, this station was closed from 20 March 1983 to 7 March 1987, and reopened as Stortinget. During the last years of the 1980s the barres and payment stalls were removed and replaced with a proof-of-payment system. This unmanning of the station allowed for a significant cut in operating costs. The Sognsvann Line was converted to a metro line from 8 April 1995, allowing Line 3 to continue onwards to Ullevål stadion from that date.