The Hardanger Line opened in 1935 as a steep and curvy branch of the Bergen Line to connect Bergen to the Hardangerfjord.[1] The line was 27.45 kilometers (17.06 mi) long, had a maximum gradient of 4.5 percent, a minimum curve radius of 180 meters (591 ft), a maximum speed of 40 km/h (25 mph), a maximum permitted axle load of 12 tonnes (12 long tons; 13 short tons), standard gauge and a 15 kV 16.7 Hz AC electrification system.[2] In 1931, NSB had taken delivery of its first electric multiple unit, the Class 62, for use on commuter trains on the Drammen Line.[3] For the Hardanger Line, NSB ordered similar units, but these were modified to have a higher power output. Three motor cars and four carriages were delivered in 1934. The mechanical components and assembly were done by Strømmens Værksted, while the electrical equipment was made by Norsk Elektrisk & Brown Boveri (NEBB). The class was similar to the future Class 65, and was regarded as a prototype.[4] Class 64 were the shortest multiple units ever used by NSB.[5]
From 21 November 1944, when the Flåm Line received electric traction, Class 64 trains were also used there.[6] The Flåm Line is even steeper and more curved than the Hardanger Line, so the trains received track brakes.[7] In 1947, El 9 locomotives were delivered for the Flåm Line.[6] Class 64 trains continued to be used periodically on the Flåm Line when there was insufficient availability of El 9s, as well as in periods with very little or very much traffic.[8]
Unit 64.07 was retired on 20 December 1982[4] after rust damage had been found on it.[7] By 1984, the carriages were in such bad shape that they needed to be replaced.[4] Trailers from Class 65 and Class 67 were taken into use, and for a short period a Class 91 trailer.[7] On 28 August 1985, passenger traffic on the line was terminated and the two remaining trains were retired. Reasons for the termination included a lack of sufficient political support for financing new trains, and also that Class 64 was no longer suitable for use.[9] The last two trains have been preserved by the Norwegian Railway Club and are stored at Garnes Station, part of the Old Voss Line.[7]
