A train driver in a locked cabin could soon be the only person staffing most of Auckland's commuter trains.
The Rail and Maritime Union claims Auckland Transport (AT) plans to scrap 160 on-board train manager positions as part of major restructure of train services.
The managers will be replaced by 18 transport officers, who AT has confirmed are already being recruited.
AT expects a law to be passed this year, giving the officers greater powers, including the ability to issue penalty notices to fare evaders.
But a spokesman said it is still consulting staff about how many roles will be scrapped and when the changes will take effect.
"Some services could operate just with a driver, but other services could operate with a driver and one or more transport officers. [It will depend] on the destination of the service and the time of day. Those details are subject to consultation."
Train managers oversee the operation of trains, and are known as conductors or guards in other parts of the world.
Union Auckland organiser Stu Johnstone said they play a critical role during emergencies, breakdowns, level-crossing incidents, and when people need first aid.
"It's the train manager on board every train that takes responsibility for every passenger.
"Without that train manager there, we have real concerns about what would happen in those situations."
Johnstone said the changes are part of a broader restructure of the train services, which could affect up to 300 union members.
He said AT needed to consider the views of workers and the peace-of-mind of passengers.
"I'm sure the public out there are quite comforted that late at night, and throughout the day, there are train managers on the train."
However, a transport commentator believes the plans could make Auckland trains faster, safer and more appealing than other transport options.
Greater Auckland blog editor Matt Lowrie said train managers are specifically told not to intervene in safety incidents between customers, but transport officers may be able to.
"If the changes mean there is more security involved, and they can actually influence and affect things, I think that will be a positive change."
Lowrie said trains actually run much faster when doors are opened by the driver, rather than by a train manager turning a key or a customer pressing a button.
"That can all help speed up time spent at journeys, and the time of the overall journey, making trains more competitive with other options.
London-based transport journalist Josh White from In Tech Today said reducing so-called "dwell times" at train stations was a good idea that was long overdue. But he said transport managers or guards are often needed on smaller networks like Auckland, with unstaffed stops.
"They do have very quiet remote stations in poorly lit areas late at night, and removing customer-facing staff may not be the best move."
He said trains on the London Underground are only staffed by drivers, but the network has regular busy staffed stops.
"Every single station has staff, and on every train there are multiple points where you can talk to the driver in case you feel unsafe or need assistance.
"I've certainly been on trains where my safety and the safety of passengers around me was threatened."
The driver would continue to the next station, radioing ahead so staff at the station were ready to help.
"Without that kind of back-up I don't think driver-only operations will make passengers feel comfortable, especially on early-morning or late-night trips."
White said a similar proposal for London's Southern Commuter Route has been very unpopular with passengers.