lines were to be built—the Grorud Line on the north side and the Furuset Line on the south side of Groruddalen and the Lambertseter Line on the east of Nordstrand. These areas were all chosen as new suburbs for Oslo, and would quickly need a good public transport system; suburban lines would first be built out extending from the existing tramway, and later a final section with tunnel to the central station would be built. The Lambertseter Line was opened in 1957, from Brynseng to Bergkrystallen while the Østensjø Line was extended to Bøler in 1958. The metro opened on 22 May 1966, when the Common Tunnel opened from Brynseng to the new downtown station of Jernbanetorget, located beside the Oslo East Railway Station. In October the Grorud Line opened to Grorud while the Østensjø Line was connected to the system in 1967 when the line also was extended to Skullerud. In 1970, the Furuset Line opened to Haugerud and extended to Trosterud in 1974, at the same time as the Grorud Line was extended to Vestli. By 1981, the Furuset Line had reached Ellingsrudåsen. The metro took delivery of T1000 rolling stock from Strømmens Værksted; from 1964 to 1978, 162 cars in three-car configurations were delivered for the eastern network. One tunnel The eastern network was extended from Jernbanetorget to Sentrum in 1977. This station was forced to close in 1983, due to water leakage, and when it opened again in 1987, renamed Stortinget, the west network tunnel had also been extended there. Through services were not possible at the time because of incompatibility of signaling and power equipment. Not until 1993 did the first trains run through the station, after the Sognsvann Line had been rebuilt to "metro standard"; the Røa Line followed in 1995. The Holmenkollen and Kolsås Lines remained non-metro, using dual mode trains that switch to overhead lines at Frøen and Montebello. The western network took delivery of 33 T1300 cars in 1978–81, with an additional 16 converted from T1000. In 1994 twelve T2000 cars were delivered for the Holmenkollen Line. In 2003 the Ring Line opened, connecting Ullevål stadion to Storo. The following year, construction work caused a tunnel to collapse on the Grorud Line—the system's busiest—forcing a shutdown of the line until December, and creating a havoc of overcrowded replacement buses. In 2006 the ring was completed, to Carl Berners plass. At the