Mission Bush Branch 10 December 1917 Open Paerata Junction Mission Bush 17 km Previously Waiuku Branch. Aickin despatched a technical mission of 4 senior officers overseas in March 1949 and travelled overseas himself to negotiate a tentative contract with a British construction firm. Aickin’s successor Horace Lusty, revised the contract with English Electric to specify DF class diesel-electric locomotives. Three G class Garratt locomotives were introduced in 1928, but these weren’t as efficient as anticipated. Electric traction in this section is now used solely by Transdev Wellington for Metlink suburban passenger services on the Kapiti Line, and was prolonged to Paraparaumu on 7 May 1983 and Waikanae on 20 February 2011. Funded by the Higher Wellington Regional Council, the extension to Waikanae coincided with the supply of recent FP class Matangi electric multiple models. Waipa Railway and Coal Co. line 1 March 1914 19 Might 1958 Ngāruawāhia Wilton Collieries 10.5 km Non-public line. 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 thirteen August 1877. It was extended to Frankton by December 1877, and to Te Awamutu in 1880. An financial downturn stalled construction for the subsequent 5 years, and Te Awamutu remained the railhead.

Auckland & Mercer Railway, for £166,000 for the 41 mi (66 km) to Mercer. In 1927, computerized color-mild signalling was put in from Otahuhu to Mercer. Development started in 2017, and trains had been switched onto the new alignment over the 2019 Easter long weekend (19-22 April). Work on electrification of the Auckland network started in 2010. The primary revenue electric services using AM class EMUs commenced on 28 April 2014 between Waitematā and Onehunga on the Onehunga Line. On 14 February 1909, the first NIMT specific left Auckland for Wellington, an overnight trip scheduled to take 19 hours quarter-hour, with a sleeping car, day vehicles with reclining seats, and postal/parcels vans. Wellington’s Metlink suburban network, operated by Transdev Wellington, contains the southern portion of the NIMT between Wellington and Waikanae as the Kapiti Line. The North-South Junction section from Plimmerton to South Junction, north of Pukerua Bay and Muri, and North Junction to Paekākāriki had been duplicated in 1940. From 24 July 1940 electrification at 1500 V DC of the southern part of the NIMT from Wellington to Paekākāriki was completed. Wikimedia Commons has media related to North Island Predominant Trunk.

This included the building of the famous Raurimu Spiral to allow trains to ascend the steep grade from the Whanganui River valley to the North Island Volcanic Plateau. It had fewer stops than the Overlander, stopping solely at Papakura, Hamilton, Ōtorohanga, Nationwide Park, Ohakune, Palmerston North and Paraparaumu. By the beginning of 1908, there was a 39 km (24 mi) hole between Erua and Ohakune, with a connecting horse-drawn coach service. The completion of Auckland’s electrification leaves a gap of 87.1 km (54.1 mi) to the central NIMT electrification at Te Rapa, north of Hamilton. The report beneficial electrification from Waikanae to Palmerston North be 25kV AC, with a change over just north of Waikanae to allow multi-current electric locomotives to modify between AC and DC traction. The economics of the project was greatly undermined by the fall of the price of oil in the 1980s and the deregulation of land transport, which removed the lengthy-distance monopoly NZR held when the cost-benefit report was written. The electrification project on the Auckland community, together with the Auckland-Papakura section of the NIMT, was completed in July 2015, with all suburban services being electric. In 2012-13, four bridges near Rangiriri between Auckland and Hamilton had been replaced.

In 2021 a new commuter service between Hamilton and Auckland was launched, named Te Huia. The explanations given for the choice included the truth that the EFs are now near their end of life (roughly 30 years outdated) and suffer from frequent breakdowns (on common each 30,000 kilometres (19,000 mi) which is well under the expected breakdown-free service interval of 50,000 kilometres (31,000 mi)) and that having to change from a diesel locomotive to an electric one and again once more at each finish of the electrified section is labour-intensive, time-consuming and provides to costs. A two-day NIMT service began on 9 November, with an in a single day stop at Ohakune (for northbound passengers) or Taumarunui (for southbound passengers). 25 kV AC, the same system as on the central NIMT. Aickin had previously been Workers Superintendent and Chief Legal Advisor to the Division and considered utilizing diesel locomotives for trains on the NIMT to be too expensive. Less gasoline could be needed and employing regenerative braking in electric locomotives lowers the fuel consumption further. As the two electrification systems are different, multi-present locomotives or a number of models can be required for by means of electric working.