Highway crashes climbing after speed limit rise, expert says

Saturday, 20 June 2026

A year on from speed limit reversals on State Highway 6 between Nelson and Blenheim, crash numbers are starting to climb, according to an expert who has analysed crash data.

However, the New Zealand Transport Agency (NZTA) says caution is needed in interpreting short-term changes in crash data as it is not possible to attribute crashes to a single factor, such as speed limits.

Sections of SH6 between Nelson and Blenheim dropped from 100kph to lower limits in December 2020, then went back to 100kph in June 2025 under Government policy.

University of Auckland senior lecturer in transportation planning Dr Tim Welch said data showed there was an upward trend in crashes on all sections of the road since speed limits were increased.

According to Welch’s software analysis, in the five years prior to the speed limit dropping, the road averaged 23.8 crashes per year. When the speed limit was dropped to 60kph or 80kph, that figure became 12.5. In the 12 months since the speed limit drop was reversed, there has been an average of 17.2 crashes.

The figures, which had nearly halved, were now climbing back upwards again, he said.

In the Rai Valley to Whangamoa Saddle stretch, there were 50 crashes in total in the five years before lower limits, and 22 in the four and a half years when speeds were dropped. Since then, in 12 months, there have been 11 crashes.

The figures showed a 74% decrease in the annual rate of death and serious injury during the period of lower limits, and a 47% decrease in the overall number of crashes.

There were a number of interventions on the road, such as guard rails, so it was impossible to say the changes were 100% speed related, Welch said.

However, crashes after the speed-limit reversal starting to climb was a “pretty good indication” that speed was a significant portion of the previous reductions.

NZTA director of regional relationships top of the south Emma Speight said crashes were complex, unpredictable events, involving multiple factors.

“The past five years have also included periods where travel patterns were significantly affected by Covid-19 restrictions, which further limits the ability to draw meaningful conclusions about trends.

“Caution should be taken when interpreting short-term changes in crash data, as it is not possible to attribute crashes to a single factor, such as speed limits. In addition, where speed limits have not been in place for long, the data may not be directly comparable to the period prior to the change.”

However, Welch’s analysis found that traffic barely changed because of Covid, measuring a -6% drop in corridor traffic during the lower-limit years. It also showed that per vehicle kilometre, there were 44% fewer crashes.

According to a 2024 WSP economic assessment report for NZTA, the predicted drop in death and serious injury crashes after the speed limit was lowered on the road was 22%, while the actual change was 82%.

In that report, lowered speeds on the corridor were estimated to have a net benefit of $18.6m a year.

According to data cited by the Royal Australasian College of Surgeons (RACS) in a submission to the Government in 2025, 50% of major trauma in New Zealand is transport related.

Road safety continued to be a “significant public health and societal issue”, the submission said, and the burden on health services had a direct impact on the ability of the wider healthcare system to provide timely non-trauma and non-emergency related services.

RACS Trauma Committee chair Chris Wakeman said Christchurch was the major trauma centre for the South Island, and saw nearly 600 major traumas a year, some of whom would have been transferred from the top of the south.

That meant at any time there would be 10 to 15 road traffic injuries who would be inpatients at Christchurch Hospital, a “significant” workload.

Wakeman said the Government needed to “resurrect” the Road to Zero.

Welch said what was happening on SH6 was occurring across Auckland and on all of the country’s state highways where speeds had been lifted after a period of crashes falling.

The decision to implement reversals was a “100% political” and wasn't backed by any kind of science or data that had been produced in the last 50 years, he said.

That years of community advocacy was wiped away instantly with a stroke of a pen was “frustrating”.

“This wasn't done for a sensible reason for a logical end result, but possibly for some political gain, and that's really playing with people's lives in the worst possible way.”

Minister for Transport Chris Bishop said National had campaigned on reversing blanket speed limit reductions and had delivered on that promise.

Bishop said over 65% of submitters supported the Government’s plan to reverse the speed limit reductions in the draft speed limit rule.

The Government was focused on drugs and alcohol as the leading factors in road deaths, he said.

It was also encouraging safer driver behaviour, promoting safer vehicles, and improved road infrastructure, Bishop said.