Trucking industry says it's not to blame for pothole plague

Trucking advocates are rejecting the government's claim that massive vehicles introduced onto New Zealand roads just over a decade ago are to partly to blame for the subsequent rise in reports of potholes.

In the first 10 months of 2022 there were 555 complaints of vehicle damage caused by potholes reported to Waka Kotahi, up from 421 in all of 2021 - a rise of about 58 percent.

In 2020, there were just 298 complaints.

"It shows what Kiwis have been feeling on the roads for some time, but I think there would be a whole lot more people over summer who have had this experience with potholes," Ia Ara Aotearoa chief executive Nick Leggett told Morning Report.

"Obviously it's costly, it delays trips and it's also a safety concern as well. That's concerning because we've got 'road to zero' in the background, and it just is another area where the government is not meeting those targets."

Before the summer break, National Party transport spokesperson Simeon Brown regularly tweeted pictures of and news stories about potholes, prompting a lengthy series of tweets in response from Transport Minister Michael Wood.

Wood dug up a number of alleged causes, including a freeze in roading maintenance under the previous National-led government, an 'extremely wet winter", and National's decision in 2010 to allow 50MAX trucks - which can weigh up to 50 tonnes - on certain roads.

Wood said these "heavier trucks do a lot more damage" owing to something called the "fourth power law". Basically, the more weight each axle of a vehicle is required to bear, the damage done to the road increases exponentially, to the power of four - so an axle bearing 10 tonnes, for example, would put 10,000 times as much stress on the road as one carrying a single tonne.

Brown tweeted that Wood was "digging his own pothole", saying Labour had years to fix the problem but "all the minister has got is to blame the previous [government]".

Leggett said Waka Kotahi's website cites peer-reviewed studies on 50MAX trucks which prove, due to "the way their axles are configured … they distribute the weight evenly".

"They're no heavier on the road than any truck that was previously on the road. It's an easy and a cheap shot, but it's not one that's backed up with evidence."

Bigger trucks also meant fewer trips, he said, resulting in fewer carbon emissions.

A spokesperson for the minister told RNZ the government has boosted its road maintenance budget by 50 percent to "help bring our roads back up to scratch", and over the next few years will invest $7 billion into renewing "around 7000 lane kilometres of state highway and 18,000 lane kilometres of local roads".

"High volumes of rainfall affected both state highways and local roads last year, making it a very challenging environment, particularly regarding potholes.

"In August the Minister of Transport sought assurances from Waka Kotahi that there was a clear plan to communicate to the public around why potholes were appearing on parts of the network, and the repair plan.

"Waka Kotahi contractors nationally have been working around the clock to address the impact of the recent severe weather events on the state highway network."

In the 2021/22 financial year, the spokesperson said more than 45,000 potholes were repaired on state highways alone - and Waka Kotahi was in the middle of "undertaking the largest ever programme of spring and summer state highway renewals".

Leggett said that highlighted another problem, however.

"To be fair to the government, they have injected more money … right at the time when we've got a labour shortage, and that means that sometimes it's harder for contractors to get work done," said Leggett. "But there's so much work to do, it's overwhelming."