Auckland's light rail project is "absolutely" going ahead, according to the minister in charge of both Auckland and transport.

Michael Wood's resolute commitment comes at a time when many state highways across the country are in dire need of repair in the wake of Cyclone Gabrielle.

But the minister says, now more than ever, it is important to invest in climate-friendly infrastructure.

"I am absolutely committed to this city and making these investments," he said on Thursday. "We cannot continue to kick the can down the road."

That would mean Prime Minister Jacinda Ardern's pledge ahead of the 2017 general election would appear to be coming to fruition.

"I am utterly determined about this," Wood said. "If there was such a thing as a spirit animal then mine is a donkey. I just keep going with these things, and I'll keep going with this one until we get it done."

Much of the North Island was still grappling with the aftermath of Cyclone Gabrielle, communities cut-off and state highways wiped out. 

But Wood said the massive repair jobs around the country could go hand-in-hand with Auckland's light rail network.

"Just this week we've invested an additional $250 million to make sure that we can get those roads fixed for people who need them in the regions. So, we're keeping an eye on that job.

"But if we just do that and don't fix the hole in the roof - which is climate change - by giving people more climate-friendly choices, we're only doing half the job." 

The Treasury had given a wide range in its budget estimates for the light rail project - between $7.3 billion and $29.2 billion. However, Wood doubted the project would reach the upper limit of this range.

"The project in 2021 dollars, when the indicative business case was set, is approximately $11 billion. In inflated terms, over the delivery timeframe of the project, it's approximately $14 billion."

The light rail corridor was expected to link up with Auckland's other rail project: the City Rail Link. But there was still no firm timeline or budget for that project.

And although the chief executive of City Rail Link (CRL) said there would be a new timeline in place by the end of last year, that can was now being kicked down the road further.

"Obviously, with a huge project like that, you have a little bit of uncertainty; you can't give an exact date or an exact week," Wood said.

"I think we'll have much more clarity by about the middle of the year."

City Rail Link work on Lower Queen Street, early 2022. Photo: City Rail Link

CRL construction led to severe disruption and hardship for many businesses around Auckland's Albert Street. Auckland Light Rail chief executive Tommy Parker said he would bear these lessons in mind.

"We know that there's a lot of concern out there around disruption, around the challenge of building these big projects in an urban area.

"We know we can learn a lot from CRL and from other projects and do things better."

Parker also said Auckland's flooding and cyclone damage of the last month would have a big bearing on the project going forward.

"It's definitely brought to the top of mind resilience planning, making sure that we're getting a resilient route, and considering the effects of climate change."

Gribblehirst Park in Sandringham was one of 30 sites along the indicative route of the Auckland Light Rail project.

Engineers were boring holes 10-80m deep at the sites to test soil samples, which would help them create a 3D picture of the conditions below ground along the proposed corridor.

The initial stage of light rail would extend 24km from the city centre to Māngere. After that, the plan was to extend light rail west to Kumeū and north to Orewa.

North Shore Ward councillor Chris Darby said, despite Mayor Wayne Brown's scepticism, there was widespread support for the project around the council table.

But as for who was going to pay for all these tracks, he said it would absolutely not be the council.

"Let's be clear about that. It is a project of national significance taking place in Auckland, being funded directly from government."

Auckland Light Rail said further ground investigations would take place over the next six months, confined mainly to parks and reserves to minimise disruption to residents.