 In 1954 , the Oslo City Council decided to build a four @-@ line metro to the new suburbs to the east of the city center . The plans called for the system to open in 1966 , with the conversion of the Østensjø Line and the Lambertseter Line of the Oslo Tramway , and the new Furuset Line and Grorud Line . The system would feature higher and longer platforms , allowing step @-@ free access to six @-@ car trains , automatic train protection and third @-@ rail power supply . This would make the metro incompatible with the existing tramways in Oslo . The first units in the T1000 series were two single @-@ car prototypes designated T. They were test @-@ run on the existing tramways from 1959 to 1960 , and were then put into service on the Kolsås Line . Prone to technical faults , they were taken out of regular service in 1982 . 
