Auckland Rail Network - Third and Fourth Main Line


The section of the train line from Wiri to Westfield on the North Island Main Trunk Line (NIMT) is an extremely important part of Auckland and New Zealand’s transport system. The line, which currently consists of two tracks, carries Auckland suburban rail services, inter-regional freight, and freight to and from Ports of Auckland at Wiri.

The line is at operational capacity, with up to 12 passenger services and two freight services per hour. Indeed, it is the busiest single section of freight rail in the country with around 4-5 million tonnes of freight carried every year. Congestion on the line already causes delays to freight and passenger rail services and unreliability for customers.

In 2017 a joint case for investment was made by KiwiRail, NZTA and Auckland Transport. The National-led Government campaigned on building a third main line at the 2017 election, as did the current Government. However, since 2017 the project has stalled.

In 2017, the case for investment said that building a third main from Westfield to Wiri would immediately deliver the following outcomes:

  • 300 hours per annum freight travel time savings due to increased reliability.
  • Three minute travel time saving for five million rail passenger journeys per annum.
  • An additional three-car rail unit made available for commuter passenger use on the network.
  • At least 400 fewer heavy vehicles on the State Highway network each week with associated decongestion and road safety benefits.
  • A step change in the performance of the national freight rail network for key journeys such as Wellington and Tauranga to Auckland.

The third main will complement the City Rail Link, by improving capacity on the network, and help drive economic growth in South Auckland.

In 2020, as part of the NZ Upgrade Programme, the government committed $315 million for the Wiri to Quay Park project (the third main) with work beginning at the end of 2020.

Fourth Main

The case for investment in 2017 noted that “The 4th Main will be almost certainly be required in the medium to long term horizon” and building both the third and fourth main line came out ranked first in the Multi-Criteria Analysis carried out in the study.

National’s view is we should get on with building the third and fourth main lines immediately. As the report noted, “building the 3rd Main and 4th Main (or some component parts) together could result in cost synergies” and “The 4th Main has been found to be an important project…and it is clear that it will be a critical piece of infrastructure as the Auckland rail network develops, delivering substantial passenger and freight benefit.”


The third main line has been costed in the NZ Upgrade programme at $315 million, although the 2016 business case put the upper estimate of the cost at $80 million
We have conservatively worked on the basis that doing the third and then the fourth main would cost an additional
$200 million.

You can find a copy of the Factsheet here