At the end of the war in 1945, the line was in need of a major overhaul, in particular the overhead wires. Lack of materials and money caused the extraordinary maintenance to take four years. Limitations of freight were imposed in 1946, and were terminated the following year. At the same time, the Kolsås Line services were internally numbered 9, but it was first many years later that the number appeared on the destination signs and schedules. Until 1951, the line had had constant fares since 1939; a 27% fare increase in 1951 was not sufficient to cover the 170% cost increase in the same period. The following year, Oslo Sporveier's Gullfisk were transferred to Bærumsbanen and designated Class E.
