NSB Di 3 - Operation

Operation

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.

The first section of the Bergen Line, the Gjøvik Line and the Roa–Hønefoss Line, was electrified in February 1961. This allowed diesel and electric locomotives to haul all trains from Oslo to Bergen. In 1962 the Nordland Line was completed to Bodø, but the increased need for locomotives was more than compensated by the electrification of the Bergen Line being extended to Ål. The first Di 3 ran on the Røros Line in 1964, that had previously been denied due to bridges with insufficient axle load permits. In 1965, the Bergen Line was electrified, and all but one Di 3 was transferred to Trondheim. A single unit, usually no. 610, was stationed at Finse Station as a snowplow. Along with additional deliveries, there were sufficient Di 3 units to terminate most steam operations.

After the Bergen Line was electrified, the work continued on the Dovre Line. The section from Hamar to Otta was finished in 1967, and the following year to Dombås. This allowed the locomotives to be transferred to secondary lines. With the final delivery of the last units in 1969 and the completion of the electrification of the Dovre Line in 1970, the final steam locomotive was taken out of service. During the last half of the 1960s, the Di 3 was put into service on the Rauma Line, the Røros Line, the Solør Line, the Valdres Line and the Meråker Line.

In November 1970, the Dovre Line was electrified, and the last steam locomotives were retired. A long-term plan to electrify half the lines was finished, and for two decades, NSB's operations were very stable with no major investments to infrastructure or closing of lines. NSB had slightly less diesel locomotives than they needed, but plans to order additional Di 3 was never fulfilled. In 1981, NSB took delivery of five Di 4 to supplement the older units. They were mainly used on the Nordland Line, and Di 3 units were predominantly used on the other lines, although they continued to operate som trains on the Nordland Line. On 1 April 1987, a Di 3 612 caught on fire; the damage was small enough that it could have been repaired, but NSB instead decided to put aside the unit. At the time NSB planned to order additional Di 4, but these plans were put on hold. In 1988, the Valdres Line was closed; this was the only time a line with Di 3 in regular service was closed.

During the 1980s, NSB started leasing SJ T44-locomotives from Sweden to supplement the Di 3. In 1992, the decision was made to order 12 Di 6 and 20 Di 8 to replace the Di 3. The former was based on the Di 4 and had twice the power of the Di 3. The Di 8 was slightly more powerful than the Di 3, and were intended for freight trains. Both series were put into service in 1996, but the Di 6 proved to have so many technical problems that they were returned to Siemens in 1998. The Di 3 units had been set aside and some had been scrapped, but the return of the Di 6 forced NSB to put the units back into service.

During the mid-1990s, NSB had initiated a program to replace the traditional locomotive and carriage trains with new, tilting multiple units. This had led to the order of sixteen Class 73 four-car units for the three mainline routes on the Bergen Line, Dovre Line and Sørland Line. To supplement this, the board of NSB decided on 14 November 1996 to purchase seven tilting diesel multiple units for the Røros and Rauma Lines. The choice fell on Class 93, with fifteen units eventually delivered. This allowed all passenger trains on diselized lines to either be operated with Class 93 be hauled by the Di 4. The last Di 3-hauled train ran on 7 January 2001.