The initial use for the Di 3 was to operate the three non-electrified long-distance lines of NSB: the Bergen Line, the Dovre Line and the Nordland Line. Following the delivery of the first batch in 1957, they were from 2 June used on the Dovre Line, north of Otta to Trondheim, and further north along the Nordland Line to Mo i Rana. The stock was sufficient to replace all steam locomotives on the Nordland Line, and reduced travel time by one hour. From Hamar to Otta, the track did not have sufficient permitted axle load. From the second batch of eight units, five were put into service on the Bergen Line, the rest on the Dovre and Nordland Lines. Necessary upgrades of the permitted axle load had been made to the Dovre Line and Nordland Line, and the locomotives were in use from Hamar to Saltdal. On 30 November, the Nordland Line was completed to Fauske, and the full length operated with Di 3.