Southern Line (Auckland)#Third Main Line

From Waitematā to Newmarket, Southern Line services use the Newmarket Line, then follow the North Auckland Line to Westfield Junction, and thence onto the North Island Main Trunk (NIMT) line as far as Pukekohe, the terminus of the Southern Line. In its entirety, this line follows the original 1875 North Island Main Trunk route between central Auckland and Pukekohe.

The line, originally single-tracked, was duplicated, piecemeal, between 1909 and 1939. In 1915, the original single-track Parnell tunnel was bypassed by a twin-track tunnel. The older tunnel can be seen alongside the current one, between Parnell station and Newmarket Junction.

In 1930, the Westfield Deviation opened a new eastern route for the NIMT between Auckland and Westfield via Glen Innes. The route between Auckland and Westfield via Newmarket then ceased to be part of the NIMT. The portion between Newmarket and Westfield became part of the North Auckland Line (NAL), which runs between Westfield and Whangārei.

The Southern Line suburban services continued to run on the older route. A new line, called the Eastern Line, was introduced for services on the new route. While the Eastern and Southern lines have a different route between Auckland and Westfield, they share the same tracks between Westfield and Puhinui station.

A future third main line is under construction as part of the Wiri to Quay Park project announced in 2017; work started in 2020 and is to be completed by 2025. {{cite web|url= https://www.kiwirail.co.nz/our-network/our-regions/amp/the-third-main-line/ |title= The Third Main Line |publisher= KiwiRail |date= 2023 }} It is expected to ease congestion on Auckland rail lines by allowing "through" trains to pass stationary trains at stations, improve rail freight access from the Port of Auckland to the Westfield yards and allow more frequent passenger and freight services.{{cite web|url=https://wdcsitefinity.blob.core.windows.net/sitefinity-storage/docs/default-source/meetings/agendas-2017/170627-inf-agenda-open.pdf?sfvrsn=0|title=Agenda for a meeting of the Infrastructure Committee - 5.9 Hamilton to Auckland Passenger Rail – Progress Update and Future Direction|last=|first=|date=27 June 2017|website=Waikato District Council|access-date=|archive-date=13 April 2021|archive-url=https://web.archive.org/web/20210413225143/https://wdcsitefinity.blob.core.windows.net/sitefinity-storage/docs/default-source/meetings/agendas-2017/170627-inf-agenda-open.pdf?sfvrsn=0|url-status=live}} The new line would be between Westfield and Wiri. {{cite web|url= https://www.kiwirail.co.nz/our-network/our-regions/amp/the-third-main-line/ |title= The Third Main Line |publisher= KiwiRail |date= 2023 }}

These improvements will avoid an estimated 175,000 annual freight movements on the state highway network. Work began at the end of 2020. The $315 million funding package for these works was announced as part of the Government's New Zealand Upgrade Programme.

{{main|Auckland railway electrification}}

Along with the rest of Auckland's suburban railway network, the Southern Line was electrified from Waitematā to Papakura, with electric services beginning in 2014. Services between Pukekohe and Papakura were initially provided by diesel multiple units (DMUs). In 2020, as part of the New Zealand Upgrade Programme, the government announced $371 million in funding to extend electrification from Papakura to Pukekohe. The project was completed in early 2025, and electric train services from Pukekohe commenced on 3 February 2025.{{Cite web |title=Electric trains to Pukekohe |url=https://at.govt.nz/projects-roadworks/electric-trains-to-pukekohe/ |access-date=8 June 2023 |website=Auckland Transport |language=en-nz}}{{cite web |date=3 February 2025 |title=Trains return to Pukekohe after two-year station closure |url=https://www.rnz.co.nz/news/national/540681/trains-return-to-pukekohe-after-two-year-station-closure |publisher=RNZ |access-date=3 February 2025}}

As part of the Pukekohe electrification project, new stations are to be built at Drury, Ngākōroa and Paerātā.{{cite news |last1=Coughlan |first1=Thomas |title=Government announces billions of infrastructure spending, with roads the big winner |url=https://www.stuff.co.nz/national/119105125/government-announces-billions-of-spending-with-roads-the-big-winner |accessdate=2 February 2020 |work=Stuff |date=29 January 2020 |archive-date=1 February 2020 |archive-url=https://web.archive.org/web/20200201204225/https://www.stuff.co.nz/national/119105125/government-announces-billions-of-spending-with-roads-the-big-winner |url-status=live }}

Suburban services are operated by Auckland One Rail under the AT Metro brand.

• Public transport in Auckland
• List of Auckland railway stations

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Category:Railway lines in New Zealand

Category:Public transport in Auckland

Category:Rail transport in Auckland