North Island Main Trunk
The North Island Main Trunk 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 long and passes through Paraparaumu, Palmerston North, Taihape, National Park, Taumarunui, Te Kuiti, Hamilton, and Pukekohe.
Most of the NIMT is single track with frequent passing loops, built to the New Zealand rail gauge of. The line is double track between Wellington and Waikanae, between Hamilton and Te Kauwhata, and between Meremere and Auckland Britomart. Around of the line is electrified in three separate sections: one section at 1600 V DC between Wellington and Waikanae, and two sections at 25 kV AC: between Palmerston North and Te Rapa and between Papakura 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 for the young nation, 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, the Northern Explorer 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.
History
Construction
Auckland to Te Awamutu
Auckland's first railway was the line between Point Britomart and Onehunga via Penrose, opened in 1873.It was built by Brogdens. The section from Penrose to Onehunga is now called the Onehunga Branch. The line was later continued south from Penrose into the Waikato. Possibly to support the Invasion of the Waikato, a tramway was built from Maungatawhiri to Meremere in 1864, though turning of the first sod of the Auckland and Drury Railway took place in 1865, a year after the last major battle. This line reached Mercer by 20 May 1875, with from Ngāruawāhia being constructed by the Volunteer Engineer Militia and opened on 13 August 1877. It was extended to Frankton by December 1877, and to Te Awamutu in 1880. An economic downturn stalled construction for the next five years, and Te Awamutu remained the railhead. There were also negotiations with local Māori, and the King Country was not accessible to Europeans until 1883.
Wellington to Marton
The Wellington-Longburn section was constructed between 1881 and 1886 by the Wellington and Manawatu Railway Company. The company was acquired by the New Zealand Railways Department in 1908.Central North Island
In 1882 the Whitaker Ministry passed the North Island Main Trunk Railway Loan Act, 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. 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.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 apart, and contracts for three massive viaducts 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.
By the beginning of 1908, there was a 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 had not yet been handed over to the Railways Department.
Opening
The gap was closed on 7 August 1908 for the first through passenger train, the 11-car Parliamentary Special carrying the Prime Minister Sir Joseph Ward and other parliamentarians north to see the American Great White Fleet at Auckland. But much of the new section was temporary, with some cuttings north of Taonui having vertical batters and some unballasted sections of track. Ward drove the last spike on 6 November 1908, and the 'Last Spike' monument is at Manganui-o-te-Ao, near Pokaka. A two-day NIMT service started on 9 November, with an overnight stop at Ohakune.On 14 February 1909, the first NIMT express left Auckland for Wellington, an overnight trip scheduled to take 19 hours 15 minutes, with a sleeping car, day cars with reclining seats, and postal/parcels vans. The dining car went on the north express from Wellington to Ohakune, then transferred to the southbound express, so avoiding the heavy gradients of the central section.
Upgrades and Deviations
The rails and signalling have been upgraded over the years, and many sections of the line have been deviated: The original 1870s Vogel Era track had rails of 40 lb/yd, some were iron not steel; later rails were 53 lb/yd ; and from 1901 70 lb/yd, e.g. between Taumarunui and Taihape for the heavy X-class locos used on the central mountainous section from 1908. Some 10 bridges between Frankton and Taumarunui had to be strengthened, and in 1914 there was still 129 km of 53 lb/yd rail to be replaced. In the 1930s 85 lb/yd was adopted, then 91 lb/yd, and from 1974 100 lb/yd.Signalling on the single-track sections was controlled by Tyer's Electric Train Tablet No 7 system; with each of the stations for the 94 tablet sections staffed by three tablet porters each working a 56-hour week for continuous coverage; hence each station required at least four houses for the stationmaster and three porters. Pierre noticed that with CTC station buildings and even platforms had been removed as there were no longer any staffed stations between Ohakune and National Park. The Train Control system introduced from 1928 to 1932 supplemented the tablet system by operators at the four sections to expedite operation of trains over several tablet sections; the 1925 Fay-Raven report urged its adoption because of the fitful progress of mixed trains, with locomotives often kept waiting. From 1938 to 1966 Centralised Traffic Control gradually replaced the Tablet system on the NIMT. In 1957 when the installation of CTC over the remaining 354 km commenced, it was estimated that using CTC over the 330 km Taumarunui to Otaki section with control centres at Ohakune, Taihape and Palmerston North would replace 74 men in traffic working duties. The last section converted was Piriaka-Owhango.
In 1913, the maximum speed limit on the NIMT was raised to, reducing the journey time by 1 hour 25 minutes Auckland-Wellington or to 17 hours and between 30 and 45 minutes. Under T. Ronayne, the Railways Department general manager from 1895 to 1913, the section south to Parnell was duplicated and improvements made to the worst gradients and tight curves between Auckland and Mercer. Under his successor E. H. Hiley the second Parnell Tunnel with two tracks and an easier gradient was completed in 1915–1916. On the Kakariki bank between Halcombe and Marton a deviation reduced the 1 in 53 grade to 1 in 70. A 1914 Act authorised spending on the Westfield Deviation, new stations at Auckland and Wellington, track doubling, and grade easements from Penrose to Te Kuiti, but the war delayed most of these works for over a decade.
In 1927, automatic colour-light signalling was installed from Otahuhu to Mercer. In 1930 the signalling was extended to Frankton and the from there to Horotiu was doubled. The north to Ngāruawāhia was doubled from 5 December 1937, followed by Ngāruawāhia to Huntly on 4 December 1938 and Huntly to Ohinewai and Papakura to Paerata in December 1939. By then, wartime shortages delayed further double-tracking. Pokeno to Mercer was doubled from 11 November 1951, Pukekohe to Pokeno 21 November 1954, Mercer to Amokura 1 July 1956 and Ohinewai to Te Kauwhata 14 December 1958. The between Amokura and Te Kauwhata remain single track, as does Ngāruawāhia bridge.
through the eastern suburbs on the Westfield deviation to the North Island Main Trunk.
In 1930, the Westfield Deviation was opened, creating a new eastern route from Auckland to Westfield via Glen Innes and Hobsons Bay, running into the new Auckland railway station and providing better access to the Port of Auckland. The original section between Auckland and Westfield via Newmarket later ceased to be part of the NIMT: Auckland to Newmarket became the Auckland-Newmarket Line, and Newmarket to Westfield became part of the North Auckland Line which runs between Whangarei and Westfield.
In the late 1930s, bridges replaced level crossings at Ohinewai, Taupiri and Hopuhopu.
, including two long tunnels. The deviation is the centre two tracks, with the Wairarapa Line's Ngauranga station in the background, alongside State Highway 1.
The double track Tawa Flat deviation opened to goods trains on 22 July 1935 and to passenger trains on 19 June 1937, bypassing the original single track WMR line between Wellington and Tawa. With a pair of tunnels under the Wellington hills, the deviation alleviated issues with more and heavier freight traffic on the steep and twisting original route where long sections at 1 in 60 gradient required banker engines. The Wellington to Johnsonville section of the original line was retained as the Johnsonville Line and the Johnsonville to Tawa section closed.
The sections from Plimmerton to South Junction, north of Pukerua Bay and Muri, and North Junction to Paekakariki were duplicated in 1940. From 24 July 1940 electrification at 1500 V DC of the southern section of the NIMT from Wellington to Paekakariki was completed. The Tawa Flat deviation has a long tunnel not suitable for steam operation because of excessive smoke. A Centralised Train Control system was installed in 1940, so that new signal boxes were not required and five stations between Tawa and Pukerua Bay no longer had to be continually staffed for Tablet operation; see Kapiti Line. Electrification eliminated the need to relieve the steep gradients from Plimmerton to the Pukerua Bay summit by a deviation to the east and allowed more frequent suburban passenger trains.
The difficult section down the Paekakariki Escarpment from Pukerua Bay to Paekakariki with five tunnels between South and North Junctions remains single track. Duplication from Tawa to Porirua opened on 15 December 1957, from Porirua to Paremata on 7 November 1960, and Paremata to Plimmerton on 16 October 1961. The section between Porirua and Plimmerton was straightened in conjunction with the duplication by reclaiming land along the eastern shore of Porirua Harbour.
Between 1964 and 1966, a deviation away from the centre of Palmerston North via the Milson deviation on the edge of the city.
In 1967, the floors of the tunnels on the former WMR section between Paekakariki and Pukerua Bay were lowered to enable the DA class locomotives to travel all the way to Wellington.
Between 1973 and 1981, the major Mangaweka deviation in the central section between Mangaweka and Utiku was built, with three viaducts, all over 70m tall, crossing the Rangitikei and Kawhatau rivers.
The central section from Te Rapa near Hamilton to Palmerston North was electrified at 25 kV AC between 1984 and 1988 as part of the Think Big government energy programme. Some tunnels were opened out or bypassed by deviations while in others clearances were increased, and curves eased. The section between Ohakune and Horopito was realigned with three viaducts replaced to handle higher loads and speeds. The most notable bridge replaced was the curved metal viaduct at Hapuawhenua by a modern concrete structure, though the original has been restored as a tourist attraction.
In 2009–10, the 1.5 km section of line between Wellington Junction and Distant Junction was rebuilt from double track to triple track, to ease peak-time congestion.
In February 2011, duplication between Paekakariki and Waikanae was completed as part of the upgrade and expansion of the Wellington suburban network; see Kapiti Line for more information.
In 2012–13, four bridges near Rangiriri between Auckland and Hamilton were replaced. The bridges were all over 100 years old with steel spans and timber piers, and were replaced by modern low-maintenance concrete ballast deck bridges. Bridges 479, 480, 481 & 482 were replaced, with lengths of,, and respectively.
The construction of the Peka Peka to Otaki section of the Kapiti Expressway required 1.3 km of the NIMT immediately north of Otaki station to be realigned. Construction began in 2017, and trains were switched onto the new alignment over the 2019 Easter long weekend.
, south of Auckland. Freight is an important revenue earner for the North Island Main Trunk.
In the Auckland area, a third main line between Wiri and Westfield is under action; this will allow freight trains to bypass stationary passenger trains.
Electrification
There are three independent sections of the NIMT which are electrified: Auckland's urban network and the central section from Palmerston North – Te Rapa at. Wellington's urban network is electrified at ; as formerly used in other sections of the New Zealand network. In Wellington the operating voltage has been increased to 1700 V DC since the full introduction of the Matangi EMU, to increase the power available.Electrification of the NIMT was mooted by electrical engineer Evan Parry in the first volume of the New Zealand Journal of Science and Technology in November 1918. In light of a national coal shortage following World War I, Parry argued that the network was under great strain due to ever-increasing volumes of freight, and the use of steam traction was partly to blame. Parry also noted that there was great potential for cheap hydro-electricity generation in the central North Island to power electrification.
The first part of the NIMT to be electrified was the Wellington–Paekakariki section via the Tawa Flat deviation that was completed on 24 July 1940. This was largely to prevent smoke nuisance in the 4.3 km No. 2 tunnel, and to provide for banking on the Paekakariki to Pukerua Bay section. Electric traction in this section is now used only by Transdev Wellington for Metlink suburban passenger services on the Kapiti Line, and was extended to Paraparaumu on 7 May 1983 and Waikanae on 20 February 2011. Funded by the Greater Wellington Regional Council, the extension to Waikanae coincided with the delivery of new FP class Matangi electric multiple units.
Following the Second World War railway services suffered due to skill and coal shortages. Skilled staff sought employment opportunities elsewhere in the economy. From 1948 to 1951 the General Manager of the Railways Department, Francis William Aickin, advocated electrification of the entire line, despite protests from his engineering staff. Aickin had previously been Staff Superintendent and Chief Legal Advisor to the Department and considered using diesel locomotives for trains on the NIMT to be too expensive. He turned his attention to electrification, mainly because he saw that it could relieve the coal situation and prevent high expenditure on imported fuels.
He commissioned a study into electrification, which concluded that a low-frequency AC system could be cheaper than 1500 V DC, the system in use in Wellington. Aickin sent a technical mission of four senior officers overseas in March 1949 and travelled overseas himself to negotiate a tentative contract with a British construction company. The Chief Mechanical Engineer and Chief Accountant specified and costed the system and Aickin was able to complete a substantial report justifying the NIMT electrification and submit it to the Government.
Officers from New Zealand Treasury and the Ministry of Works and two experts from Sweden commented on the proposal and in December 1950 the Government granted approval in principle and agreed to appoint Thelander as a consultant. However, Aickin fell out with the then National Government and retired as General Manager in July 1951. With the change in regime, the electrification proposal disappeared.
A key assumption of Aickin's report was that traffic on the NIMT would grow by 50% from 1948 to 1961. Since a diesel-electric locomotive is a travelling power station, the savings through electrification compared to diesel could be regarded as the difference between the cost of buying bulk electrical energy generated substantially from New Zealand resources and the cost of generating electricity in a small plant using imported diesel fuel.
The Royal Commission on Railways created following Aickin's tenure rejected the report's findings. Aickin's successor, H.C. Lusty, revised the tentative contract with English Electric to specify DF class diesel-electric locomotives. They were later found to be unreliable, and only ten were supplied. 42 DG class locomotives were supplied instead for secondary lines. For main lines including the NIMT, the General Motors G12 export models were ordered, becoming the DA class.
The section between Palmerston North and Hamilton was electrified at 25 kV 50 Hz AC, opened on 24 June 1988 as one of the Muldoon National Government's "Think Big" energy development projects. An overall cost in excess of $100 million had been projected, with some 40% being for the locomotives, but the final cost was about $250 million. 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 long-distance monopoly NZR held when the cost-benefit report was written.
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.
Electrification's advantages were reflected in the economic evaluation in the report, which showed a rate of return of 18%. Sensitivity analysis showed that this high rate of return gave the project robustness against lower traffic volumes than expected, against significant increases in construction cost, and against lower than expected rises in the diesel fuel price.
Part of the project included replacing the copper wire communications system with a new fibre optic communications cable between Wellington and Auckland. In 1994 New Zealand Rail Limited sold the cable to Clear Communications for telephone traffic, leasing part of it back for signalling.
Proposals to electrify the Auckland suburban rail network dated back to the 1960s, they mainly coincided with proposals to electrify the NIMT in its entirety. In 2005 the central government decided to implement a proposal to electrify the urban network at 25 kV AC, the same system as on the central NIMT. This included of the NIMT itself, from Britomart to just south of Papakura. Work on electrification of the Auckland network began in 2010. The first revenue electric services using AM class EMUs commenced on 28 April 2014 between Britomart and Onehunga on the Onehunga Line. The electrification project on the Auckland network, including the Auckland-Papakura section of the NIMT, was completed in July 2015, with all suburban services being electric. A diesel shuttle service runs on the non-electrified Pukekohe-Papakura section.
The future
The completion of Auckland's electrification leaves a gap of to the central NIMT electrification at Te Rapa, north of Hamilton. Electrification may be extended south as the Auckland suburban system expands, but this will depend on further government funding. In February 2008 former Auckland Regional Council Chairman Mike Lee suggested the initial electrification might be extended to Pukekohe, leaving a gap to Te Rapa. In 2012, in response to public submissions, the board of Auckland Transport decided to include an investigation into electrifying to Pukekohe to its 10-year programme. ATAP, Auckland's 2018–2028 plan provides for Pukekohe electrification, a third line from Westfield to Wiri and further new electric trains. In 2020 the government announced funding for electrification from Papakura to Pukekohe.A paper written in 2008 for then railway infrastructure owner ONTRACK investigated the possibility of electrifying the remaining Papakura-Te Rapa gap between the Auckland urban system's terminus at Papakura on the NIMT and the central NIMT system, along with electrification of the East Coast Main Trunk to Tauranga. The report put the total cost of electrification at $860 million, with $433 million for the Papakura-Te Rapa section. It concluded that money would be better spent on grade and curvature easements, removing speed restrictions and increasing the length of passing loops.
In Wellington, there is an gap from Waikanae to the central NIMT electrification at Palmerston North. Since the extension of electrification to Waikanae in February 2012, there have been calls for the electrification to be extended by to Otaki. If this happens, there will be a gap. As the two electrification systems are different, multi-current locomotives or multiple units would be required for through electric working, should that gap be ever closed, unless one electric system is converted to be consistent with the other.
On 21 December 2016, KiwiRail announced their plan to withdraw from service, over a two-year period, the EF class electric locomotives without replacing them. The reasons given for the decision included the fact that the EFs are now close to their end of life and suffer from frequent breakdowns and that having to change from a diesel locomotive to an electric one and back again at each end of the electrified section is labour-intensive, time-consuming and adds to costs. KiwiRail did not intend to de-electrify the section but would maintain it so that electric rolling stock could be reintroduced in the future.
On 30 October 2018, the Government announced that it is retaining the EF class electric locomotives, to help meet its long term emissions goals and boost the economy. The 15 remaining EF class locomotives will be refurbished by KiwiRail and will continue to run between Hamilton and Palmerston North.
| Section | Length | Traction | Percentage of total |
| Wellington to Waikanae | 57 km | DC | 8.4% |
| Waikanae to Palmerston North | 81 km | none | 11.9% |
| Palmerston North to Hamilton | 404 km | AC | 59.2% |
| Hamilton to Pukekohe | 79 km | none | 11.6% |
| Pukekohe to Papakura | 26 km | future AC | 3.8% |
| Papakura to Britomart | 35 km | AC | 5.1% |
Centennial
On 6 August 2008, at 9am, a train departed Wellington in a re-enactment of 7 August 1908 Parliamentary Special carrying the Prime Minister Sir Joseph Ward to Auckland, stopping overnight at Taihape and Taumarunui before continuing to Auckland. Tickets were by invitation only.A series of stamps was issued to commemorate the centennial, see :
- 50c – Last Spike Ceremony Manganui-o-te-ao – a photo of actual event
- $1.00 – Taumarunui, 1958 – steam locomotive KA 947 pulling into the old railway station.
- $1.50 – Makatote Viaduct, 1963.
- $2.00 – Raurimu Spiral, 1964.
- $2.50 – The Overlander, Hapuawhenua Viaduct, 2003.
Infrastructure
The NIMT includes 352 bridges and 14 tunnels. The major viaducts include three opened in 1981 for the Mangaweka deviation. Five viaducts are over high. There are smaller viaducts at Taonui north of Ohakune, and Manganui-o-te-Ao and Mangaturutura.
The heights and lengths of the main viaducts are:
| Name | Height | Length | Opened | Remarks |
| North Rangitikei | 1981 | on Mangaweka deviation | ||
| Makatote | 1908 | |||
| South Rangitikei | 1981 | on Mangaweka deviation | ||
| Kawhatau | 1981 | on Mangaweka deviation | ||
| Makohine | 1902 | |||
| Toi Toi | 1904 | |||
| Hapuawhenua | 1908 | replaced 1987 | ||
| Hapuawhenua | 1987 | |||
| Waiteti | 1889 | or Waitete, long | ||
| Mangaweka | 1903 | superseded by Mangaweka deviation in 1981 |
Rolling stock
Due to its high volume and high value of traffic to NZR and the steep grades in the central section, the NIMT has seen the use of the most powerful locomotives in New Zealand.When the NIMT opened in 1909, the powerful 4-8-2 X class was introduced to handle heavy traffic over the mountainous central North Island section.
Three G class Garratt-type locomotives were introduced in 1928, but these were not as effective as anticipated. In 1932 the 4-8-4 K class was introduced, and later improved in 1939 with the KA class.
The introduction of the DF class in 1954 began the end of the steam era, and in 1955 with the introduction of the DA class locomotive, major withdrawals of steam locomotives began. 1972 saw the introduction of DX class locomotives and the Silver Fern railcars; the latter remaining in service between Auckland and Wellington until 1991.
With electrification and the introduction of the EF class electric locomotives in the late 1980s, the DX class was mainly reassigned to other areas of the network, including hauling coal on the Midland Line in the South Island. Since then services between Te Rapa and Palmerston North have been worked mainly by the electrics, although some services are still diesel-operated, such as those originating from or terminating on other lines, or originating from within the central section, like the paper pulp freight trains from Karioi.
As of May 2020, regular rolling stock on the NIMT include:
| Class | Image | Type | Cars per set | Number | Operator | Routes | Built |
| FP/FT Matangi | EMU | 2 | 83 | Transdev Wellington | Wellington suburban services between Wellington and Waikanae | 2010–12, 2015–16 | |
| AM | EMU | 3 | 57 | Transdev Auckland | Auckland suburban services on Eastern and Southern Lines | 2012–15 | |
| ADL/ADC | DMU | 2 | 10 | Transdev Auckland | Auckland passenger services between Papakura and the town of Pukekohe | 1982–85 | |
| S | carriage | 8 | 8 | KiwiRail | Capital Connection services between Wellington and Palmerston North | 1971–75 | |
| AK | carriage | 6 | 6 | KiwiRail Scenic Journeys | Northern Explorer services between Wellington and Auckland Strand Station | 2011–12 |
- DC class – all sections
- DFT class – all sections
- DL class – all sections
- DX class – all sections
- EF class – Palmerston North to Te Rapa
Connecting lines
| Line Name | Date Opened | Date Closed | NIMT Junction | Terminus | Length | Notes |
| Newmarket Line | 24 December 1873 | Open | Quay Park Junction | Newmarket Junction | 2.5 km | Formerly Auckland-Onehunga line 1873–1877, Auckland-Waikato line 1877–1908, NIMT 1908–1974. |
| North Auckland Line | 20 May 1875 | Open | Westfield Junction | Otiria Junction | 280 km | Formerly formed part of the NIMT in conjunction with what is now the Newmarket Line. |
| Manukau Branch | 15 April 2012 | Open | Wiri Junction | Manukau | 2.5 km | |
| Mission Bush Branch | 10 December 1917 | Open | Paerata Junction | Mission Bush | 17 km | Formerly Waiuku Branch. Glenbrook Vintage Railway uses the 8 km Glenbrook-Waiuku section. |
| Kimihia Branch | 21 October 2015 | Huntly North | Kimihia Mine | 2.75 km | ||
| Rotowaro Branch | 20 December 1915 | Open | Huntly | Rotowaro | 8.5 km | Formerly Glen Afton Branch. Bush Tramway Club uses the 2 km section Pukemiro to Glen Afton. |
| Waipa Railway and Coal Co. line | 1 March 1914 | 19 May 1958 | Ngāruawāhia | Wilton Collieries | 10.5 km | Private line. Operated by NZR from 12 August 1935 to closure. |
| East Coast Main Trunk | 20 October 1879 | Open | Frankton Junction | Kawerau | 180 km | Formerly Thames Branch. Line reduced in length by Kaimai Deviation, 1978. Former length 230 km. |
| Stratford–Okahukura Line | 4 September 1933 | Mothballed 2009 | Okahukura Junction | Stratford | 144 km | Leased to Forgotten World Adventures Ltd. |
| Raetihi Branch | 18 December 1917 | 1 January 1968 | Ohakune Junction | Raetihi | 13 km | |
| Marton–New Plymouth Line | 4 February 1878 | Open | Marton Junction | Breakwater | 212 km | |
| Taonui Branch | 17 November 1879 | 14 August 1895 | Taonui | Colyton | 3.5 km | |
| Palmerston North–Gisborne Line | 9 March 1891 | Open | Roslyn Junction | Gisborne | 391 km | Napier-Gisborne section mothballed 2012. Gisborne City Railway use Gisborne-Muriwai section |
| Foxton Branch | April 1873 | 18 July 1959 | Longburn Junction | Foxton | 31 km | Part of Foxton-New Plymouth Railway until 1908 |
| Wairarapa Line | 14 April 1874 | Open | Distant Junction | Woodville | 170 km | Reduced in length by closure of Rimutaka Incline from 182 km. |
| Johnsonville Branch | 24 September 1885 | Open | Wellington Junction | Johnsonville | 10 km | Built by the Wellington and Manawatu Railway Company. 6 km Johnsonville-Tawa section closed 19 June 1937. |
| Te Aro Branch | 27 March 1893 | 23 April 1917 | Wellington | Te Aro | 1.77 km |
Notable connecting tramways and other lines
| Junction Station | Date Opened | Date Closed | Owner | Notes |
| Drury | 1862 | unknown | Drury Coal Company | Horse tramway |
| Kellyville | Public Works Department | Construction of Pokeno to Paeroa line, not completed beyond Mangatawhiri. | ||
| Ngāruawāhia | 1 March 1914 | 19 May 1958 | Waipa Railway and Coal Co. | 10 km private railway. |
| Otorohonga | 1921 | Rangitoto Colliery Co. | 6 km horse tram | |
| Mangapehi | 1944 | Ellis and Bernand | Steam-powered bush tramway | |
| Waione Siding | 1950 | Marton Sash and Door Co | Steam-powered bush tramway | |
| Ongarue | 1956 | Ellis and Bernand | Extensive steam-powered bush tramway | |
| Taringamotu | 1910 | 1960s | Taringamotu Tramway | Steam-powered bush tramway |
| Manunui | 1944 | Ellis and Bernand | Extensive steam-powered bush tramway | |
| Oio | 1935 | King Speirs and Co | Steam-powered bush tramway | |
| Mansons Siding | Manson and Clark | Steam-powered bush tramway | ||
| Raurimu | 1935 | King Speirs and Co | Steam-powered bush tramway | |
| Raurimu | 1935 | 1957 | Raurimu Sawmilling Co | Steam-powered bush tramway |
| Pokaka | 1930 | 1957 | Pokaka Timber Co | Steam-powered bush tramway |
| Horopito | Horopito Sawmills Ltd | Highest railway in New Zealand, summit at 923.5 metres above sea level. | ||
| Longburn | 27 October 1886 | 7 December 1908 | Wellington and Manawatu Railway Company | Private line, purchased by NZR and incorporated into NIMT |
Passenger services
Long-distance
From opening, there have been regular passenger services between Wellington and Auckland. The daily "Express" left earlier in the evening, followed by the "Limited", which had fewer stops for passengers.Between 1963 and 1968, daytime trains were called the Scenic Daylight. In 1968, a Drewery RM class articulated 88-seater railcar was refurbished and repainted in a distinctive blue-and-white scheme that led to it being nicknamed the Blue Streak. It initially operated an unsuccessful service between Hamilton and Auckland in early 1968, and was transferred to the Auckland-Wellington run on 23 September 1968. Note that all self-propelled passenger railcar classes in New Zealand are generically classed 'RM'.
In 1971 NZR introduced the Silver Star, a luxury sleeper train. The service was not economically viable, and was withdrawn in 1979. Much more successful was the Silver Fern, a daytime railcar service, introduced in 1972 to replace the "Blue Streak". This service was withdrawn in 1991 and replaced by The Overlander.
In conjunction with the introduction of the carriage train Overlander service, the Silver Fern railcars were redeployed to start new services between Tauranga and Auckland – Kaimai Express, and Auckland and Rotorua – Geyserland Express, in 1991. In 2000 a new commuter service called the Waikato Connection was introduced between Hamilton and Auckland and ran in conjunction with the services to Tauranga and Rotorua until all three services were cancelled in 2001. In 2019 a new commuter service between Hamilton and Auckland was proposed, to be named through a public competition. The Covid-19 pandemic of 2020 has delayed progress of this proposal.
On 25 July 2006, Toll announced that the Overlander would cease at the end of September 2006, but on 28 September 2006, the train's continuation on a limited timetable was announced. It ran daily during the summer months and thrice-weekly for the balance of the year.
In 2012, KiwiRail announced the Overlander would be replaced by the Northern Explorer, with modern New Zealand-built AK class carriages to provide a premium tourist train on a quicker timetable with fewer stops. It commenced on Monday 25 June 2012, and consists of one train running from Auckland-to-Wellington on Mondays, Thursdays and Saturdays, and Wellington-to-Auckland on Wednesdays, Fridays and Sundays. It has fewer stops than the Overlander, stopping only at Papakura, Hamilton, Otorohanga, National Park, Ohakune, Palmerston North and Paraparaumu. Along with the other tourist rail services—the Coastal Pacific and TranzAlpine, and the Interislander rail-ferry services across Cook Strait, the Northern Explorer is operated by The Great Journeys of New Zealand, a division of KiwiRail.
The Capital Connection commuter train operates between Palmerston North and Wellington.
Both KiwiRail and private enthusiast operators such as the Railway Enthusiasts Society, Mainline Steam and Steam Incorporated operate charter trains.
Auckland suburban
Suburban trains run on the NIMT at regular intervals as follows:Eastern Line trains run on the NIMT between Puhinui and Britomart.
Southern Line trains run on the NIMT from Papakura to Westfield Junction. They then run on the North Auckland Line to Newmarket, and the Newmarket Line to the vicinity of Quay Park, where they rejoin the NIMT only for the short section into Britomart. A diesel train shuttle service runs on the NIMT between Pukekohe and Papakura.
Onehunga Line and Western Line trains use the NIMT only for the short section from the vicinity of Quay Park into Britomart.
Wellington suburban
Wellington's Metlink suburban network, operated by Transdev Wellington, includes the southern portion of the NIMT between Wellington and Waikanae as the Kapiti Line.Stations
| Station | Distance from Wellington | Height above sea level | Opened | Closed | Notes |
| Wellington | 0 km | 2.4m | 1937 | Open | Replaced NZR's Lambton and WMR's Thorndon stations, which closed upon completion. |
| Lambton | 0 km | 2.4m | 1884 | 1937 | Slightly north of current Wellington station. |
| Pipitea | 0.75 km | 2.4m | 1874 | 1884 | Original Wellington station, on Pipitea Quay. |
| Thorndon | 0.75 km | 2.4m | 1886 | 1937 | Wellington and Manawatu Railway Company, near of Pipitea station |
| Kaiwharawhara | 2.44 km | 2.4m | 1874 | 2013 | Kaiwarra until 1951. |
| Takapu Road | 11.78 km | 41m | 1937 | Open | |
| Redwood | 13.16 km | 26.5m | 1963 | Open | |
| Tawa | 13.58 km | 25.6m | 1937 | Open | Tawa Flat was 12 metres above Redwood station on adjacent hillside. |
| Linden | 14.85 km | 17.7m | 1940 | Open | |
| Kenepuru | 16.16 km | 15m | 1940 | Open | |
| Porirua | 17.8 km | 3.6m | 1885 | Open | |
| Paremata | 21.7 km | 2.7m | 1885 | Open | |
| Mana | 23.04 km | 3m | 1949 | Open | Dolly Varden until 1960. |
| Plimmerton | 24.4 km | 5.8m | 1885 | Open | |
| Pukerua Bay | 30.1 km | 80m | 1885 | Open | |
| Muri | 31.15 km | 77m | 1952 | 2011 | |
| Paekakariki | 38.84 km | 7m | 1886 | Open | |
| Wainui | 40.85 km | 9m | 1886 | 1900 | |
| Paraparaumu | 48.28 km | 13.7m | 1886 | Open | |
| Otaihanga | 51.5 km | 21m | 1886 | 1902 | |
| Waikanae | 55.31 km | 31m | 1886 | Open | |
| Hadfield | 60 km | 39m | 1886 | 1906 | |
| Te Horo | 64.77 km | 19.2m | 1886 | 1965 | |
| Hautere | 67.6 km | 15.2m | 1886 | 1900 | |
| Otaki | 70.28 km | 14.6m | 1886 | Open | |
| Manakau | 79.3 km | 30.5m | 1886 | 1982 | Known as "Manukau" until 1905. |
| Ohau | 84.95 km | 30.7m | 1886 | 1982 | |
| Levin | 90.3 km | 36.5m | 1886 | Open | Known as "Weraroa" 1886–1894. |
| Queen Street | 91.37 km | 36.5m | 1956 | 1977 | |
| Levin | 91.5 km | 36.5m | 1886 | 1894 | |
| Koputaroa | 99.23 km | 8.5m | 1886 | 1986 | Kereru until 1906. |
| Shannon | 106.57 km | 12.2m | 1886 | Open | |
| Makerua | 111.84 km | 7.62m | 1886 | 1966 | |
| Tokomaru | 118.35 km | 17.7m | 1885 | 1982 | crossing loop retained |
| Linton | 124.19 km | 18.3m | 1885 | 1972 | |
| Longburn | 129.69 km | 19.8m | 1873 | 1886 | |
| Awapuni | 132 km | 24.7m | 1876 | 1965 | |
| Palmerston North | 135.76 km | 30m | 1873 | 1965 | |
| Palmerston North | 136.03 km | 28m | 1963 | Open | |
| Terrace End | 138.51 km | 38.1m | 1876 | 1964 | |
| Bunnythorpe | 144.47 km | 55.2m | 1876 | 1985 | |
| Taonui | 148.62 km | 61.9m | 1876 | 1963 | |
| Aorangi | 150.66 km | 70.7m | 1876 | 1965 | |
| Feilding | 152.98 km | 72.2m | 1876 | 2012 | except for groups of 10+ |
| Makino Road | 156.26 km | 103m | 1878 | 1960 | |
| Maewa | 158.34 km | 107m | 1878 | 1962 | |
| Halcombe | 165.76 km | 118m | 1878 | 1983 | |
| Kakariki | 171.12 km | 70m | 1879 | 1982 | |
| Greatford | 175.67 km | 104.5m | 1875 | 1983 | |
| Marton | 180.25 km | 140.8m | 1878 | 2012 | except for groups of 10+ |
| Cliff Road | 183.58 km | 159.7m | 1888 | 1966 | |
| Overton | 188.85 km | 155m | 1888 | 1958 | |
| Porewa | 190.53 km | 165m | 1888 | 1982 | service siding retained |
| Rata | 195.46 km | 194m | 1888 | 1975 | |
| Silverhope | 199.31 km | 224m | 1888 | 1966 | |
| Hunterville | 205.33 km | 267m | 1888 | 1986 | |
| Kaikarangi | 210.18 km | 284m | 1888 | 1964 | |
| Mangaonoho | 216.04 km | 257m | 1893 | 1966 | |
| Ohingaiti | 222.14 km | 279m | 1902 | 1975 | |
| Mangaweka | 231.04 km | 326.7m | 1902 | 1982 | |
| Utiku | 243.69 km | 371m | 1904 | 1986 | |
| Ohotu | 247.08 km | 395.6m | 1904 | 1959 | |
| Winiata | 249.02 km | 415m | 1905 | 1972 | was siding |
| Taihape | 251.85 km | 442m | 1904 | 2012 | except for groups of 10+ |
| Mataroa | 260.88 km | 530m | 1907 | 1986 | |
| Ngaurukehu | 270.25 km | 640m | 1908 | before 1993 | |
| Turangarere | 274.5 km | 702m | 1912 | 1972 | |
| Hihitahi | 278.2 km | 741m | 1908 | 1982 | Turangarere until 1912. "Hihitahi" is a sound-based local Maori word for "locomotive". |
| Waiouru | 290.3 km | 813.8m | 1908 | 2005 | at 814m, highest railway station in New Zealand. |
| Tangiwai | 299.49 km | 699.5m | 1909 | 1986 | Nearest station to the Tangiwai disaster, 24 December 1953. |
| Karioi | 306.94 km | 630.3m | 1909 | 1984 | |
| Rangataua | 312.79 km | 670m | 1909 | 1986 | |
| Ohakune | 317.09 km | 618.4m | 1908 | open | Ohakune Junction in working timetables 1917–1968. |
| Horopito | 326.91 km | 752m | 1909 | 1978 | Used as location for Smash Palace movie, 1981 |
| Pokaka | 332.57 km | 811m | 1909 | 1986 | |
| Erua | 340.13 km | 742.5m | 1908 | 1986 | |
| National Park | 346.83 km | 806.8m | 1908 | open | Waimarino until 1949. |
| Raurimu | 358.31 km | 589m | 1906 | 1978 | Pukerimu 1906-1908 |
| Oio | 366.25 km | 520m | 1908 | 1972 | Known to WW2 American servicemen as "Zero-10". Shortest station name in New Zealand, with Ava & Tui. |
| Owhango | 371.89 km | 456.6m | 1908 | 1985 | first closed 1983, then briefly reopened |
| Kakahi | 382 km | 266m | 1908 | closed | |
| Piriaka | 387.15 km | 230m | 1908 | 1987 | |
| Manunui | 391.9 km | 190.5m | 1908 | 1986 | |
| Matapuna | 394.8 km | 180m | 1908 | 1987 | |
| Taumarunui | 397.75 km | 171m | 1903 | 2012 | except for groups of 10+ |
| Taringamotu | 402 km | 172.5m | 1903 | 1971 | |
| Okahukura | 408.54 | 178.3m | 1903 | closed | Okahukura Junction in working timetables 1933–2010. |
| Te Koura | 412.75 km | 182m | 1909 | 1975 | |
| Ongarue | 420.68 km | 192.6m | 1903 | 1986 | |
| Waione Siding | 426.86 km | 208m | 1921 | 1950 | |
| Waimiha | 434.39 km | 232m | 1903 | 1983 | |
| Poro-O-Tarao | 444.05 km | 339.2m | 1901 | 1979 | |
| Mangapehi | 449.47 km | 285.3m | 1901 | 1984 | Known as "Mangapeehi" station 1901–1920. |
| Kopaki | 454.35 km | 265m | 1901 | 1982 | Paratikana until 1920. |
| Puketutu | 461.83 km | 206m | 1889 | 1977 | briefly open in 1889, then Mokau until 1912. |
| Waiteti | 470.07 km | 135m | 1889 | closed | |
| Te Kuiti | 475.66 km | 54m | 1887 | 2012 | except for groups of 10+ |
| Te Kumi | 478.56 km | 49.6m | 1887 | 1968 | |
| Hangatiki | 485.2 km | 39.9m | 1887 | 1982 | |
| Otorohanga | 494.41 km | 37m | 1887 | 2012 | Reopened summer 2012 |
| Kiokio | 498.45 km | 35.4m | 1887 | 1973 | |
| Te Kawa | 506.88 km | 47.8m | 1887 | 1982 | |
| Te Mawhai | 513 km | 35.6m | 1887 | 1958 | Te Puhi until 1900 |
| Te Awamutu | 517.02 km | 50m | 1880 | 2005 | |
| Ngaroto | 519.92 km | 56m | 1880 | 1954 | |
| Lake Road | 522.26 km | 54m | 1880 | 1940 | |
| Ohaupo | 527.16 km | 52m | 1880 | 1982 | |
| Rukuhia | 533.59 km | 55m | 1880 | 1970 | |
| Hamilton | 542.52 km | 37.5m | 1877 | Open | Previously Hamilton Junction and Frankton Junction. |
| Te Rapa Racecourse | 547.50 km | 33.2m | 1920 | 1980 | |
| Te Rapa | 549.25 km | 33m | 1877 | 1970 | Not to be confused with Te Rapa Marshalling Yards. To be reopened as Rotokauri in 2020 for Te Huia train. |
| Horotiu | 553.65 km | 23.7m | 1877 | c1975 | Pukete until 23 June 1907. Moved from to from Auckland in 1880 |
| Ngaruawahia | 559.16 km | 20.7m | 1877 | c1968 | Newcastle until 1878. |
| Taupiri | 566.56 km | 13.7m | 1877 | c1968 | |
| Huntly | 573.87 km | 14m | 1877 | 1998 | To be reopened in 2020 for Te Huia train. |
| Kimihia | 578.45 km | 14m | 1877 | 1939 | |
| Ohinewai | 582.04 km | 10m | 1877 | c1968 | |
| Rangiriri | 588.11 | 9m | 1877 | 1957 | |
| Te Kauwhata | 591.62 km | 12.2m | 1877 | 1984 | |
| Whangamarino | 598.34 km | 6.7m | 1877 | 1978 | |
| Amokura | 604.53 km | 7m | 1877 | 1980 | |
| Mercer | 609.16 km | 6.4m | 1877 | 1986 | |
| Pokeno | 613.96 km | 24m | 1877 | c1968 | |
| Whangarata | 617.90 km | 59.7m | 1877 | c1968 | a flag station |
| Tuakau | 621.41 km | 37m | 1875 | 1986 | rebuilt 1910 |
| Buckland | 625.6 km | 58m | 1875 | 1969 | |
| Pukekohe | 628.86 km | 60.65m | 1875 | open | |
| Paerata | 633.29 km | 45.1m | 1875 | 1980 | Paerata Junction from 1917. |
| Runciman | 638.37 km | 8m | 1875 | 1918 | |
| Drury | 640 km | 9m | 1875 | 1980 | |
| Opaheke | 642.9 km | 14.5m | 1875 | 1955 | Hunua 1877–1939. |
| Papakura | 647.02 km | 19.2m | 1875 | Open | |
| Tironui | 648.95 km | 15.5m | 1904 | 1980 | |
| Takanini | 650.64 km | 15.2m | 1875 | Open | |
| Te Mahia | 652.24 km | 14.9m | 1904 | Open | |
| Manurewa | 653.1 km | 17m | 1875 | Open | |
| Homai | 655.7 km | 30.78m | 1904 | Open | |
| Wiri | 657.6 km | 22.25m | 1913 | 2005 | |
| Puhinui | 658.92 km | 19.8m | 1904 | Open | |
| Papatoitoi | 659.63 km | 18.9m | 1875 | 1904 | |
| Papatoetoe | 660.42 km | 18m | 1904 | Open | |
| Middlemore | 662.28 km | 8.8m | 1904 | Open | |
| Mangere | 663.02 km | 10.66m | 1904 | 2011 | |
| Otahuhu | 664.15 km | 9.44m | 1875 | Open | |
| Westfield | 665.5 km | 7.6m | 1904 | 2017 | |
| Sylvia Park | 667.09 km | 7.6m | 1931 | Open | Relocated 1 km further north, 2007. |
| Panmure | 669.93 km | 17.7m | 1931 | Open | Relocated 200m north, 2007. |
| Tamaki | 671.28 km | 23.5m | 1930 | 1980 | |
| Glen Innes | 672.64 km | 22m | 1930 | Open | |
| Purewa | 675.4 km | 18m | 1930 | 1955 | |
| Meadowbank | 676.26 km | 12m | 1954 | Open | |
| Orakei | 677.44 km | 4.5m | 1930 | Open | |
| The Strand | 680.76 km | 2.7m | 1930 | Open | Was platform 7 of the 1930–2003 Auckland station. Terminus for the Northern Explorer long-distance service and steam and other excursion services. |
| Britomart Transport Centre | 682 km | 4m below sea level | 2003 | Open | Terminus for Auckland suburban electric services only. |