KiwiRail has replaced hundreds of timber sleepers along Whanganui's Castlecliff line.
An excavator was modified to run on rails and used to replace 430 treated pinus radiata timber sleepers with heavy weight concrete sleepers, KiwiRail said. The timber sleepers had reached the end of their service life.
"This job was the first of a number to be undertaken on this line over the next three years at key locations which will help to improve the overall condition of the line and help to provide a reliable service to our customers," KiwiRail said.
Freight traffic on the line has increased in recent months prompting the installation of warning signs at the Heads and Beach roads crossing.
Horizons roadsafe co-ordinator Glenda Leitao said train traffic on the line is set to treble with more freight coming and going.