Auckland rail workers will start voting next week on whether to take more industrial action over a reduction in staff.
They have been in collective bargaining with Transdev since May, and went on strike early last month.
Rail and Maritime Transport Union workers are against plans to do away with train managers and operate driver-only trains.
Organiser John Kerr said an example of why train managers are so vital was last Sunday, when a baby got clipped by a train at Meadowbank Station.
Without the train manager there, the driver would have had to manage that emergency all by himself, he said.
"We hoped that Transdev and Auckland Transport would see sense after the huge outpouring of support we had from commuters," Kerr said.
"Unfortunately they have not.
"That's why we need train managers on every train. They're first responders in medical emergencies; they ensure all passengers, including those with disabilities, can safely board and disembark; they're a deterrent to anti-social behaviour. With train managers on board, the public can feel safe knowing a skilled, uniformed member of staff is never far away.
"Strike action is the only tool we have to make management listen. We apologise to the public for the inconvenience, but we won't put them at risk and we know we have their support for that.
"We call on Auckland Council and central government to step in and tell Transdev to keep our passenger trains safe."