New Zealand EF Class Locomotive - Background

Background

The North Island Main Trunk is a 681-kilometre (423 mi) long rail line that links New Zealand's capital Wellington and New Zealand's largest city Auckland, and is one of the major backbones of the country's rail network. The line was completed in 1908 and opened the following year, and included various engineering feats on the central section between Hamilton and Palmerston North, including the Raurimu Spiral and numerous viaducts - five of which are over 70 metres (230 ft) high.

Electrification of the North Island Main Trunk was first proposed as early as 1918 due to coal shortages during World War I, and later was proposed in the 1950s when diesel locomotives started to replace steam. The section between Wellington and Paekakariki was electrified in 1938 at 1500 V DC to prevent steam build-up in the long Tawa tunnels under the Wellington hills and to provide banking on the steep seaside section from Paekakariki up to Pukerua Bay. This electrification has since been extended further north to Paraparaumu in 1983 and again to Waikanae in 2011.

Following the oil shocks of the 1970s, the National government, led by Prime Minister Rob Muldoon, launched the "Think Big" energy development projects. One of the projects involved the electrification of the 411-kilometre (255 mi) central section of the NIMT between Palmerston North and Te Rapa. This section was chosen for the topography of the line between these two cities, and the advantages electric locomotives had over diesel in this area. The 2,050-kilowatt (2,750 hp) DX class diesel-electric locomotives, then the mainstay of the NIMT and only recently introduced themselves, could handle 720-tonne freight trains on the section, but could only average 27 kilometres per hour (17 mph) when climbing the 1 in 52 gradient of the Raurimu Spiral. A more powerful locomotive however, in this case an electric locomotive, could haul a 900-tonne freight train up the same section of track at a speed of 45 kilometres per hour (28 mph). Electric trains also had their advantage with the oil shocks of the time with New Zealand being dependent on oil from the rest of the world to supply diesel locomotives. Meanwhile, New Zealand's electricity supply is mainly generated from renewable hydroelectricity (hydroelectricity generated 84.5% of New Zealand's electricity in 1980), and therefore electric trains do not have to rely on overseas oil to operate.