KiwiRail staff and contractors have replaced sleepers along 200m of track as part of a $3 million upgrade on the Castlecliff branch in Whanganui.
The work has been made possible by the Government decision to allocate money from the Provincial Growth Fund.
The upgrade will mean that mainline locomotives are able to use the Castlecliff branch line.
The investment made by central Government increases connectivity and improves resilience.
KiwiRail executive general manager operations Siva Sivapakkiam said that the stronger connections it provides will build a better regional economy.
"Two work gangs, along with contractors who provided plant, worked on the line over the weekend when there were no trains running and replaced around 300 sleepers," Sivapakkiam said.
"Installing the concrete sleepers and improving the track formation will mean the track can carry heavier axle loads and increase the line's reliability."
Work on the line will continue over coming months at a number of sites between the junction at Aramoho and Castlecliff.
The project is expected to be completed in mid-2020.