The North Island Main Trunk (NIMT) is the main railway line in the North Island of New Zealand, connecting the capital city Wellington with the country's largest city, Auckland. The line is 682 kilometres (424 mi) long, built to the New Zealand rail gauge of 1,067 mm (3 ft 6 in) and serves the large cities of Palmerston North and Hamilton. Around 520 km (320 mi)–approximately 75%–of the line is electrified in three separate sections: one section at 1500 V DC between Wellington and Waikanae (55 km, 34 mi), and two sections at 25 kV AC: 412 km (256 mi) between Palmerston North and Te Rapa (Hamilton) and 50 km (31 mi) between Pukekohe and Auckland Britomart. The first section of what became the NIMT opened in 1873 in Auckland. Construction at the Wellington end began in 1885. The line was completed in 1908 and was fully operational by 1909. It is credited for having been an economic lifeline, and for having opened up the centre of the North Island to European settlement and investment. In the early days, a passenger journey between Wellington and Auckland could take more than 20 hours; today, it takes approximately 11 hours. The NIMT has been described as an "engineering miracle", with numerous engineering feats such as viaducts, tunnels and a spiral built to overcome large elevation differences with grades suitable for steam engines, the ruling gradient being 1 in 50. When built the Makatote Viaduct was the highest viaduct in the country.
History
Construction
When the first sections of the NIMT were built, there was great uncertainty as to whether the initial terminus on the Waikato River would be Mercer, or Tuakau (see 1871 map of possible routes), and, within Waikato in 1872, Cambridge, Kihikihi, Te Awamutu and Alexandra were possible destinations. The central section was gradually extended to meet up in 1909, 23 years after the last of the northern and southern sections of NIMT had been opened.
Auckland to Te Awamutu Auckland's first railway was the 13 km (8.1 mi) line between Point Britomart and Onehunga via Penrose, opened in 1873. It was built by Brogdens, as was the rest of the Auckland & Mercer Railway, for £166,000 for the 41 mi (66 km) to Mercer. The section from Penrose to Onehunga is now called the Onehunga Branch. The line was later continued south from Penrose into the Waikato. To support the Invasion of the Waikato, a 3.5 mi (5.6 km) tramway was built from Maungatāwhiri to Meremere in 1864, with a first sod event near Koheroa on Tuesday, 29 March 1864 by Auckland's Chief Superintendent of Roads & Bridges, W R Collett. Turning of the first sod of the Auckland and Drury Railway took place in 1865, a year after the last major battle. By 1867 the Provincial Government had run out of money and an Amendment Act was passed. In 1870, the resident engineer proposed cutting costs by reducing the gauge from standard to 3 ft 6 in gauge, though rolling stock had been bought for the wider gauge. In 1872 contracts were let to Owen Jones and to Brogdens and work was soon reported as well under way. This line reached Mercer by 20 May 1875, with 29 km (18 mi) from Ngāruawāhia being constructed by the Volunteer Engineer Militia and opened on 13 August 1877. It was extended to Frankton by December 1877, to Ōhaupō on 4 June 1878 and to Te Awamutu on 1 July 1880. An economic downturn stalled construction for the next five years, and Te Awamutu remained the railhead. There were negotiations with local Māori, and the King Country south of Te Awamutu (from the boundary of the Puniu River) was not accessible to Europeans until 1883.
Wellington to Marton The Longburn to Marton section had been opened on 18 April 1878, as part of the line linking the ports of Foxton and Whanganui. The Wellington-Longburn (near Palmerston North) section was constructed between 1881 and 1886 by the Wellington and Manawatu Railway Company (WMR). The company was acquired by the government and merged with the New Zealand Railways Department in 1908.
Central North Island
In 1882, the Whitaker Ministry intiated the North Island Main Trunk Railway Loan Act, which was passed by the General Assembly, to expedite construction of the North Island Main Trunk south of Te Awamutu by authorising the overseas borrowing of a million pounds for the work, with the final route to be approved by the General Assembly following surveys of potential routes, for which £10,000 were allocated. From Te Awamutu, it was proposed that the line be built via Taupo or via Taumarunui, the eventual route. Four options were considered before the Minister of Public Works decided on the present route in 1884, but, when it was realised just how difficult that route was, further surveys considered two other options in 1888. Routes via Napier and Waitara were also considered, with surveying in Taranaki from 1883 to 1889. Construction of the final central section began on 15 April 1885, when paramount chief Wahanui of Ngāti Maniapoto turned the first sod outside Te Awamutu. It was 23 years before the two lines met, as the central section was difficult to survey and construct. The crossing of the North Island Volcanic Plateau with deep ravines required nine viaducts and the world-famous Raurimu Spiral. Richard Seddon’s Liberal Government pledged in 1903 that the whole route would be open in 1908. In 1904, the railheads were still 146 km (91 mi) apart, and contracts for three massive viaducts (Makatote, Hapuawhenua and Taonui) were not let until 1905. The government committed 2500 workmen, and in 1907, the Minister of Public Works William Hall-Jones instigated a night shift (under kerosene lamps). By the beginning of 1908, there was a 39 km (24 mi) gap between Erua and Ohakune, with a connecting horse-drawn coach service. From Ohakune south to Waiouru, the Public Works Department operated the train, as this section of 27 km (17 mi) had not yet been handed over to the Railways Department.
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