Rail Network Rebuild

The Rail Network Rebuild is an essential part of KiwiRail’s work to build a network that can support faster, more frequent and reliable trains for passengers and greater capacity for freight trains. 

The rebuild replaces old foundations under tracks and upgrades drainage, allowing more reliable train journeys and helps prepare the network for City Rail Link 

The work involves removing the existing tracks and digging down up to a metre to replace the aging rock foundations under the tracks, replacing ballast and upgrading drainage to improve rail’s resilience to flooding. 

The upgrades mean that the different types of speed restrictions which are in place to manage our aging rail network but slow down and can delay commuter trains, are significantly reduced.

50% complete

More than half of the Rail Network Rebuild is now complete following the completion of Stage 3 on the Western Line. The sections of the Southern and Eastern lines that have been rebuilt have seen improved reliability and train speeds – they are the best performing on the Auckland rail network. 

Work is now underway between Papakura and Pukekohe.

Carrying out significant work like this on a live network that operates 24/7 is extremely difficult. For example, if we were to do only this work in our current evening and weekend maintenance windows, it would take almost two decades to complete.

To get the majority of the work done before CRL opens, KiwiRail and Auckland Transport have made the difficult decision to close some rail lines, or sections of line, to electric commuter trains while this work is undertaken.

Find out where our teams are working and what we are doing here.

RNR Stage 1 excavating existing formation near Penrose Station
RNR map for use when Stage 3 complete v2

Current work: stage 4 - Papakura to Pukekohe

From 19 May to mid-January 2025, full upgrade and renewals works while the line remains closed for electrification. By delaying reopening the line to trains for a short time, major disruption at a later date is avoided.

Find out where we are currently working here.

Work will be carried out in phases with drainage upgrades until late July, followed by foundation replacements from August.

Night works

Much of this work needs to happen at night and on long weekends. Working at night gives our construction teams the longest possible window to work, getting more done in a shorter period.

Carrying out significant work like this on a 24/7 live network is extremely difficult. Although no commuter passenger trains are running between Papakura and Pukekohe, freight and long distance passenger trains still use this part of the rail network.
Because the project involves digging up tracks to replace foundations, working during the day would mean cancelling freight trains or working in shorter periods that are regularly interrupted – getting less done. This would extend the length of the project
by months and delay the return of passenger trains.
Our teams will be mindful of working near to residential properties and aim to get the job done as quickly and quietly as possible to minimise disruption.

Complete: Stage 3a Western Line and 3b Southern Line

Stage 3a: Major upgrades to the Western Line between New Lynn and Newmarket, including replacing aging foundations and upgrading drainage. Trains have returned to their normal frequency. Essential track work, including de-stressing rails, is being completed overnight during coming weeks.  

Stage 3b: More minor track drainage-focused work on the Southern Line between Papakura and Puhinui, to improve resilience and the performance of the rail foundations in this low-lying part of the network. The RNR team will return to this part of the Southern Line to carry out foundation replacements when funding is approved.


What we are doing

Rail Network Rebuild cross section graphic

The Rail Network Rebuild is challenging:

  • Rail lines, sleepers and turnouts (which allow trains to switch between tracks) lifted away;
  • Existing formation (compacted gravel that forms the base of the rail line) and ballast (the rocks the tracks sit on) dug out;
  • New formation brought in and compacted to form a firm and resilient base;
  • New ballast brought in and compacted
  • New drainage to prevent future deterioration of the formation;
  • The rails, sleepers and turnouts put back, aligned for safe and smooth train running.
This video shows how we replace the foundations under rail tracks.

Wherever possible we’ll also do proactive maintenance – such as replacing sleepers and trimming vegetation that would otherwise need to be dealt with in the coming years – and using the line closures to complete other rail related projects.

All railways require ongoing maintenance but we are thinking ahead and trying to avoid the need to come back and cause further disruption in the years ahead.


These photos illustrate some of the different types of work that go into the Rail Network Rebuild (RNR) .

Rail Network Rebuild work involves removing track and digging out the original formation (foundation), adding stabilizing mesh, putting in and compacting new formation, then replacing the rails and sleepers and then re-ballasting. This example at Sylvia Park includes adding a new crossover, which will improve flexibility on the network.


Using technology to get the job done quickly

To renew formation quickly, KiwiRail is using a range of specialist machines and technology. These include:

Panel lifter

The panel lifter can pick up and put down up to 75 metres of straight sections of track and sleepers at a time.

Panel Lifter

Stabilisers shake and consolidate the track formation, to ensure new formation is stable.


Tamper machines measure the track placement, lift it, and pack the ballast underneath to hold it in place. It helps create a smoother ride for passengers and freight.

Rail grinder

Rail grinders smooth irregularities in the tracks and restore their profile, so they last longer. It also helps to improve the ride for passenger and freight services.

Rail grinder

Without suspending frequent commuter services, it would be impossible to safely use much of this time-saving technology.  

Frequently Asked Questions.