Coalition negotiations and damage inflicted by extreme weather have forced a change in National's long-standing roading priorities for Northland.

Top of the new to-do list - once urgent, short-term repairs have been completed - is to build a four-lane alternative to a notoriously slip-prone section of State Highway 1 over the Brynderwyn Hills.

It's one of the key infrastructure items in the National-New Zealand First coalition deal, with the parties agreeing to at least settle the route during the current parliamentary term.

The coalition agreement makes no mention of four-laning elsewhere in Northland.

That's in contrast to National's pre-election pledge to four-lane State Highway 1 all the way from Auckland to Whangārei, except for the section over the Brynderwyns.

The party has long argued upgrading the highway is critical to unlocking Northland's economic potential.

New Northland MP Grant McCallum said the government's "ultimate vision" was still to have a four-lane highway all the way to Whangārei, but the section over the Brynderwyns was now the top priority.

"The four-laning is still alive, but in terms of the order things are done, the priorities have changed a wee bit with the coalition agreement. And, quite frankly, nature has made us look at this and forced us to make this decision, regardless of what individuals think."

The most urgent task was to shore up the current road over the Brynderwyns, which was in danger of failing entirely next winter.

The highway was closed for significant periods earlier this year due to slips triggered by Cyclone Gabrielle and other weather events.

Photo: Supplied/ Waka Kotahi NZTA

Waka Kotahi had set aside more than $60 million for more repairs later this summer, but even that was not expected to keep the highway open long-term.

"It's essential obviously we fix the current road so it's going to hang in there for the next seven to 10 years. And in the meantime we've got to work out where to put a new four-lane route around the Brynderwyns," he said.

"It's a top priority … We haven't got a specific timeline but we are racing against the clock given the current road."

Newly minted Transport Minister Simeon Brown inspected the Brynderwyns last Friday, his first site visit in his new role.

"It's pretty broken," he said.

"The reality is it's in a really bad state after recent weather events, and it's going to require significant remedial work in order to extend the life of that particular stretch of road. Visiting the site was certainly an eye-opener."

While four-laning the rest of the highway was not in the coalition agreement, Brown said National was still committed to it.

"What we said in the coalition agreement is we need to have a four-lane alternative route for the Brynderwyns. We also campaigned on a four-lane expressway from Whangārei to Auckland, so what we're doing at the moment is rewriting the government policy statement on transport to refocus it back on building the roading network, and restarting the Roads of National Significance programme."

Announcements would be made "in due course" about the timing and costs of the alternative Brynderwyn route.

Bypass goes through new MP's farm

It was unfortunate that Waka Kotahi had started work on a Brynderwyn bypass but the project had been shelved by the previous Labour government in 2017, Brown said.

At that time the roading agency came up with two alternative routes, both to the west of the Brynderwyns.

Ironically, both pass through a 620ha beef and dairy farm owned by McCallum and his family.

McCallum said he had been open about that so he could not be accused of having a conflict of interest.

He said the transport agency would re-assess the routes so they could still change.

However, if Waka Kotahi's chosen route crossed the farm, he would stand back and allow other members of his family to handle the negotiations.

Another option touted by members of Northland's influential Regional Transport Committee is to build a new route up the south side of the Brynderwyns, just east of the current highway.

That would involve building a viaduct over the Atlas Quarries site and a new road along a ridge, joining the existing SH1 at the Brynderwyns' summit.

Members of Northland's Regional Transport Committee want a new route for SH1 over the Brynderwyns to cross a viaduct over the Atlas Quarries site. Photo: RNZ / Peter de Graaf

McCallum said it was up to the experts to decide which route was best.

"Ultimately, I'm not an engineer. It's not my job to make those decisions about the routes and their suitability. That's where we need NZTA to go away and look at all options, re-assess them all, and come back to the people of Northland with what they think is the best option … If it ends up coming through our property, then so be it. The most important thing is that we get a new four-lane route because the current one is not fit for purpose."

Whichever route was chosen it would have to be compatible with long-term plans to four-lane the highway all the way to Whangārei, McCallum said.

The chair of the Automobile Association's Northland Council, Tracey Risetto, backed the government's change of focus.

"We agree the priority has to be the Brynderwyns because you can have four-laning either side, but if the road in the middle is impassable, that four-laning is not going to help," she said.

"But I do ask that we keep working on four-laning. There's been no designation of land between Marsden and Whangārei for that four-laning, for example, although there has been between Warkworth and Wellsford. We all know it will take some time but let's not drop the ball. Let's just work through what we need to do, so when we're ready to do that construction we're not starting from scratch, like we appear to be doing with the alternative Brynderwyns route."

Delay possible for short-term repairs

Rissetto said short-term repairs to keep the highway open in the meantime were also vital.

Originally Waka Kotahi planned to close State Highway 1 for slip repairs after Waitangi Day, but after an outcry from Northland businesses the agency is considering delaying the work until after Easter.

That would, however, increase the cost and extend the closure from seven weeks to 10.

"We're calling for the work to happen. We know it's going to impact Northland and the economy - up to $2 million a day - but we need a resilient network. We've got 200,000 people up in Northland and we also contribute a lot to the rest of the country. It's not just people coming up here, it's also goods and services going to the rest of New Zealand," she said.

Rissetto said the earlier timeframe for repairs would hurt tourism and hospitality businesses, but delaying the work would affect avocado and kiwifruit growers trying to send their produce south.

"So it's really a no-win … Our call is that we fix it, and then get a new route constructed as soon as possible."

The AA was also urging Waka Kotahi to upgrade the detour routes before the highway closed.

"We saw previously when the Brynderwyns were closed that the detour routes were not suitable for purpose. There are one-lane bridges and very tight corners. Critical work is needed now to get those routes ready for additional traffic, including State

Highways 12 and 14 because the large 50-tonners [trucks] are going to be requested to travel those roads," Rissetto said.

Other Northland-specific commitments in the National-New Zealand First coalition agreement include further work to examine a rail link to Northport and progressing a business case for a dry dock at Marsden Point.

The agreement also calls for an investigation into reopening Marsden Point oil refinery.

The refinery has been partly dismantled since it was closed by its private owners in 2022.

This story was originally published by RNZ