Most of Wellington's rail network will close during the Easter break to undergo crucial maintenance work and upgrades.
Work includes replacing turnouts, tunnel maintenance and signal system upgrades, with bus lines replacing trains for those still needing to commute over the long weekend.
KiwiRail said 280 staff members would be working around the clock to ensure the network was back up and running by Tuesday.
Chief asset development officer David Gordon said the disruption was necessary to ensure a more resilient network system.
"[In a] a statutory holiday, the impact on workers is as low as it can be.... but this is the time when the least number of people are getting their lives impacted by it. We don't do this lightly, but the type of work we are doing is highly invasive.
"You cannot do that with trains running around, you cannot do it safely. We're digging up holes, we're lifting the track in places and replacing it. So unfortunately, you just have to pick the time where basically the least number of people [would be] impacted."
Gordon said crews would be working around the clock.
"You have to start as soon as the last train goes, and you have to keep going until you're ready to open.
"That means that in the first couple of hours of starting, you [have to] rip everything out as quickly as you can, to give yourself as much time to put it back together."
He said the work was challenging and they had to consider unforeseen events.
"You have to allow time for things to go wrong, because something [might] come up that you need to deal with, that cannot be predicted. So, it's the putting it back together and the testing that takes time.
"You do all the physical work, then you do the signalling work, then you put a train over it, then you do the testing. You are against the clock and people want to get to work on Tuesday."
Gordon said the works would improve reliability and enable more frequent trains to run in the years ahead.
"This is all about the long-term. The work we're doing is not just about fixing today's problems - the work is about setting the network up to be able to take more traffic, to be able to deal with disruption, to be able to be maintained more easily without the need for disruption.
Chair of Greater Wellington's transport committee Thomas Nash said ongoing investment in rail should be a priority.
"I want to thank all of the maintenance crews who are giving up their Easter and time with their families to get this essential work done... [and] all of the bus drivers who are activated whenever the rail network is out of action.
"We want to get to a point where holiday train travel is the norm, rather than bus replacements. But these tracks have had years of underinvestment, so getting this work done when there are fewer people travelling is extremely important if we ever want to progress."
The work being carried out over the long weekend included replacing turnouts, tunnel maintenance, and signal system upgrade:
- Replacing a turnout near Petone, allowing trains to turn onto the Melling Line.
- Continuing work in the Remutaka Tunnel, ahead of major track replacement work at Christmas.
- Continuing work on the Fitzherbert Street (SH2) level crossing in Featherston, focused on the pedestrian part of the crossing.
- Installing cables under the Matarawa Rd and Moffats Rd level crossings around Carterton, to allow more frequent trains.
- Laying new track at Tawa, which will require the McLellan St level crossing to be closed.
- Replacing ballast around the northern end of Waikanae, with traffic management around the Hadfield Road level crossing.
- Continuing work around Wellington Railway Station to improve signals and track layout.