Government ministers will learn within weeks whether proposals to re-open Northland's partly mothballed railway and build a new rail spur to Northport stack up economically.
Officials have been working on a business case for upgrading the 250km North Auckland Line, which links Auckland to Otiria, near Moerewa, and are due to hand over their report by the end of April.
The future of Northport is inextricably linked to the railway line.
Without upgraded tracks and a new rail spur from Oakleigh to Northport, a proposal to move Auckland's bursting-at-the-seams container port to Northland won't go ahead.
Currently one train a day runs from Auckland as far as the dairy plant at Kauri, just north of Whangārei, and back.
The rest of the line, which ends at a log loading yard at Otiria, was mothballed in August 2016.
Even the tracks still in use are in poor condition and the 13 tunnels south of Whangārei are too low for modern container wagons.
The Ministry of Transport, which commissioned the business case for the upgrade and the new spur, is saying little until the report is complete.
Rail and freight manager Erin Wynne said she expected to provide ministers with advice on the business case at the end of April, plus a range of options to consider.
The business case concentrated on freight but also examined the potential for rail tourism. Passenger services in Northland were not considered.
As part of the business case officials had consulted a reference group made up of local businesses, potential rail users, NorthPort and local government. They also heard from iwi in Whangārei, Moerewa and Te Hana.
The Transport Ministry also commissioned a report looking into wider transport links across the top of New Zealand. That study, by the Upper North Island Supply Chain Working Party, was completed about six weeks ago and is due to be considered by ministers shortly.
Group chairman Wayne Brown, a former Far North mayor, said it was ''a bit early in the piece'' to be talking about moving container freight from Ports of Auckland to Northport.
However, the group concluded that doing so would be ''the best thing that could ever happen to Northland'' — but it would be a waste of time without rail.
Northport was one of the only major ports anywhere in the world without a rail link, he said.
In 2016 KiwiRail estimated the cost of renewing the North Auckland Line, not including the new spur, would be $336 million.
In 2017 Regional Economic Development Minister Shane Jones said the spur would cost up to $200m while upgrading the North Auckland Line could cost up to $600m.
''I'm not pretending it's inexpensive but these are long-term, nation-building projects.''
While the Northport spur was important, a series of hui with business and Māori had also called for the line to be reopened all the way to Otiria. Tourism groups wanted to be connected with rail tourism facilities in Kawakawa and Opua.
The business case had, however, also thrown up some important issues, not least that an upgraded North Auckland Line and a proposed Auckland light rail system would need to use the same corridors. The two projects would have to be integrated, Jones said.
''I'm not the leader of the light rail project in Auckland. I am, however, mandated to drive better rail connectivity between Auckland and Northland.''
The business case was paid for by a $500,000 grant from the Provincial Growth Fund.
Before the 2017 election, New Zealand First leader Winston Peters made a ''cast-iron commitment'' to move Ports of Auckland if he ended up in a position of power.
''The days of the Ports of Auckland as a container port and as a car yard are numbered. Aucklanders want their harbour back while Northlanders want the jobs and opportunity that would come from Northport's transformation,'' he said at the time.
All tunnels and bridges along the North Auckland Line were inspected in late 2018-early this year to determine what was needed to bring them up to modern standards. Geotechnical tests were also carried out along the proposed Oakleigh-Northport route.
When KiwiRail shut down the line north of Kauri in 2016 its sole remaining customer, wood chip maker Marusumi, had to switch to trucks to shift its logs from Otiria to its mill in Portland.
The Dargaville branch railway was closed in 2015. The Okaihau branch was closed and pulled up in the 1980s, while the Opua branch is leased to the Bay of Islands Vintage Railway Trust.