"The re-opening signals that we're open for business, ready to support importers and also building resilience and sustainability into our transport network.
"It also ties in with our ongoing efforts to address the freight backlog. Freight is core to KiwiRail's business and moving more freight by rail is a key objective."
The train is set to leave sometime after 4pm, once it has been filled with containers, and every container taken by rail means one less truck travelling on State Highway One all the way to Auckland.
Currently 30,000 containers leave Northland each year by road and lowering tracks in the tunnels means many could be transported by rail.
The upgrade included sleepers and ballast to renew or replace 54km of track, lowering the track in 13 tunnels so standard shipping containers can fit through, replacing five bridges, and improving drainage.
KiwiRail said there may still be rail maintenance vehicles on the tracks at times so motorists were urged to take care at level crossings.
Meanwhile, police will be meeting the trucks as they head to and leave the port to ensure their vehicles meet all safety standards before hauling hundreds of containers from Northport to Auckland.
This comes after police took off the road almost 20 per cent of trucks and truck-and-trailer units that transported freight for Auckland retailers from Marsden Pt just before Christmas after they failed safety checks.
The biggest concern was the 11 trucks deemed to be of non-operational standard by a police commercial vehicle safety team at Uretiti, on SH1 south of Whangārei, in the first three days of the operation.
