The electrification of the section, which had its genesis in a study group set up in June 1974 to report on measures to be taken to cope with increasing rail traffic volumes, received approval in 1980. This led to a technical study carried out with assistance from the Japanese Railway Technical Research Institute. The report stated that track capacity would be increased by electrification because such traction is faster and able to move more freight at once. The report stated, for example, that whereas a diesel locomotive could haul 720-tonne trains at up the Raurimu Spiral, an electric locomotive could haul 1100/1200-tonne trains at , cutting 3–5 hours off journey times. Less fuel would be needed and employing regenerative braking in electric locomotives lowers the fuel consumption further.