Transport commentators and mainlanders say the South Island has missed out on its fair share of transport funding.

The government's National Land Transport plan for the next three years is worth nearly $33 billion and focuses on more state highways, road maintenance, and greater public transport in big cities.

Auckland alone has secured $8.4b - more than twice as much as the entire South Island, which has been allocated $3.9b across its regions. That was up from $2.78b in the last three-year plan.

The South Island's roads had been consistently underfunded by successive governments, but this disparity felt more extreme, Dunedin City councillor Jim O'Malley said.

"It didn't come as a surprise, it just comes as a disappointment, largely," he said.

"Everybody got ... a good spread of the budget when it comes to things like potholes and other such things, but when it comes to things like the roads of national significance and the roads of regional significance, then you really start seeing the South Island, and especially the lower South Island, just disappearing from the list."

Of the 17 roads of national significance, just two were in the South Island.

But safety improvements were desperately needed on highways in and around southern cities, O'Malley said.

"There's a section of road south of Dunedin that's only about 10k's [kilometres] long, [that] has one of the worst deaths and serious injury rates in the country.

"They are doing some work there, but that needs to be turned into a separated highway, but we'll never get anything like that."

Auckland public transport commentator and blogger Matt Lowrie said funding would naturally fluctuate, for example, Waikato had a decent chunk of change over the last decade while the expressway was built.

"But if you look at the long-term trend, the South Island particularly gets underfunded, against ... places in the North Island," he said.

"Just because there are some new roads that have been built doesn't mean there's not other things that are needed, like better public transport."

There were plenty of opportunities for improvement in the South Island, he said.

Even those who stood to benefit from the transport plan pointed out the South Island's share seemed a little light.

Transporting New Zealand Ia Aotearoa advocates for road freight companies, and its interim chief executive Dom Kalasih said there would always be more transport work to do than the government could afford.

"There was always going to be some good projects missing out, and arguably the South Island, that's missed out a little," he said.

But on the whole, the government's road-heavy transport plan priorities were "dead right", Kalasih said.

"At the end of the day, you need freight and goods and people to be able to move around for the economy to grow and prosper."

RNZ asked Transport Minister Simeon Brown about the South Island's share of funding, but he passed the query on to Waka Kotahi.

The transport agency said most regions received significantly more than in the last three-year plan.

"Consistent with the strategic priority of economic productivity and growth, a significant focus of the 2024-27 NLTP will be progressing the Roads of National Significance projects," it said.

"With the majority of these located in the North Island, this has an impact on the distribution of investment in the 2024-27 NLTP."

On top of that, road maintenance spend generally aligned with population - but that varied due to things like geotechnical conditions and weather patterns, it said.

Data from the 2023 census showed 75 percent of New Zealanders live in the North Island, with 25 percent calling the South Island home.