Commuters who rely on the Capital Connection train link have said they may lose their jobs or be forced to retire if it is axed.
The connection between Palmerston North and Wellington is under threat after KiwiRail said it was evaluating whether it will continue the service given falling numbers and a lack of funding for the line.
But the announcement has left many reeling.
"If the train is cancelled, then ostensibly, I'll be looking at potentially losing my job," daily commuter Bob Pearce told TV One's Close Up.
The capital connection has been running since 1991.
It is the only public transport line between Wellington and Palmerston North - a 140km journey, which takes two hours.
Despite KiwiRail's claims of falling numbers, it has a loyal patronage, with an average 320 passengers every service.
And passengers Close Up spoke to said the train carriages are often full, describing it as "standing room only" on busy days.
"It's absolutely crucial," said Pearce.
"The reason I got this job in Wellington was because I knew I could catch the train every day to get me to work, and I could come home every evening."
He said he was "distraught" when he heard the NZTA were considering closing the line.
"This is my lifeline to my employment," he said.
"If the train was cancelled, at a minimum, we'd have to buy another car, I'd have to drive to Waikanae every day, and that would just add extra pressure and stress."
His fears were shared by another commuter, Justin Cole, who finds himself in a similar situation.
"If it's cancelled, I'm going to have to look at moving to Waikanae or Wellington or somewhere closer, where we can use the train service, or I'm going to have to look at finding another job," he said.
Janet MacDonald has been catching the Capital Connection for the past 20 years.
She said she will have to retire if the service is cancelled.
"I don't think I'd want to go through all this, especially not in the winter, I wouldn't do that train-bus-bus-train or whatever," she said.
"I don't have a car, so I'm reliant on public transport.
"And what's wrong with that? Any western country has a decent public transport system, and other countries overseas embrace rail - they want it, people use it."
The Capital Connection is the only commuter rail service in New Zealand which doesn't receive a Government subsidy.
Deb Hume, KiwiRail passenger manager, admitted the situation was "really difficult" for commuters.
"We appreciate that," she said.
"KiwiRail's been very clear - we just can't run a service at a loss.
"We're not even breaking even, we're losing money every day.
"So we, the collective we, are trying pretty hard to find a solution. We just haven't worked out what that is at the moment."
The NZTA said the service doesn't meet its funding criteria.
In a statement from Jenny Chetwynd, central regional manager, NZTA said the case is still being reviewed, in partnership with the Ministry of Transport and Treasury, and officials from Greater Wellington Regional Council.
"The decision is not just one about NZTA funding," she said.
"The business case raises wider issues concerning ownership of the rolling stock and other assets, whether any continued service would be managed as part of the TranzMetro network.
"These all need to be worked through together.
"We expect this work will take another few days - it is important that the right decision is made, based on a thorough understanding of the facts."