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.
