Almost 3km of railway line between Trentham and Upper Hutt has been double-tracked so commuter services and freight trains can pass by each other rather than wait in a queue.
Transport Minister Michael Wood announced today that the first stage of Wellington's rail upgrades have been completed.
"By having two tracks between Trentham and Upper Hutt, we've cleared a bottleneck where commuter services and freight trains sometimes got in each other's way, making services more reliable," Wood said.
Other upgrades completed include a freight loop at Upper Hutt, new platforms and shelters at both Trentham and Wallaceville stations, improved parking facilities and level crossing safety upgrades.
Wood said trains on the Wellington network provide 14 million passenger journeys a year.
"Passenger numbers are forecast to keep growing - our upgrades will keep that growth on track by supporting more services."