Auckland's train service connecting Papakura and Pukekohe will be suspended from September next year until the end of 2024.
The service will be replaced with buses and then restart once the 19-kilometre section is upgraded to allow electric trains to run on it.
KiwiRail and Auckland Transport say it means work can done to extend Auckland's existing electric train service to Pukekohe.
Auckland Transport general manager Mark Lambert said the alternative would see years of disrupted journeys and a delayed completion date.
He said early 2025 should also see the opening of new stations at Drury Central and Paerata.
"The new stations will provide convenient access for locals and commuters in the south will no longer need to change trains at Papakura.”
Pukekohe Station is also undergoing major redevelopment. Once complete, a new platform layout will be able to accommodate longer trains and the existing station building will be replaced with modern facilities.
KiwiRail’s chief operating officer Todd Moyle said the City Rail Link (CRL) will be game changing for Auckland “allowing more frequent and more convenient commuter services to get people around the city".
“Most of this work will require at least one track, and often two, to be closed at multiple locations along the route.
"Without suspending the commuter service, we would not be able to get the work done safely on schedule for the opening of the CRL."
He said there was a lot of work being done to improve Auckland’s rail network over the coming years, it’s a long process to modernise the existing tracks.
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