KiwiRail has confirmed it will cut 158 infrastructure and engineering jobs by the end of October and outlined which regions will be affected.
The company's infrastructure and engineering general manager Rick van Barneveld said staff will be told this week which roles were going to be disestablished.
The company divides its operations in to three regions: southern (all of the South Island), central (Wellington to Tongariro National Park) and northern (Tongariro National Park to north of Whangarei).
Of the 158 redundancies, 42 will be the nothern region, 58 in the central area, 40 in the southern region and 18 will be from the track machine team and railweld which operates around the country.
In all, KiwiRail is reducing its 714-strong infrastructure and engineering work force to 556.
"We've worked very closely with the union and staff to ensure all those affected have the information they need, and understand the process," van Barneveld said.
He said more than 70 workers had taken voluntary redundancy but added mandatory redundancies were unavoidable - although the exact number was not yet known as attempts would be made to redeploy workers.
KiwiRail would begin working with affected staff from early October, and recruitment in to the new structure will be complete by the end of October.
The state-owned enterprise is looking to shave $200 million from its books over the next three years and there is talk of a second round of job cuts in March.
Critics say the cuts are part of the Government's plans to privatise the company.
But Van Barneveld said the restructure of the infrastructure and engineering business was "part of a wider programme to rebalance KiwiRail's priorities in response to continuing economic uncertainty".
KiwiRail employs 4100 staff nationwide.