More than half of survivors in a New Zealand-based study of major trauma were injured on the roads.
Thirty per cent of the patients suffered their injuries in motor vehicle crashes and a further 26 per cent were injured while "vulnerable road users" such as motorcyclists, cyclists or pedestrians.
Half suffered a brain injury.
These are the findings of a study published today in the New Zealand Medical Journal. They emerge five days after one of the country's deadliest road crashes - other than bus fatalities - which killed eight people.
The sole survivor, 9-year-old David Poutawa, was discharged from Hawke's Bay Hospital yesterday. Both of his parents and five of their children died in the head-on smash at Atiamuri, north of Taupo, on State Highway 1 on Sunday.
It helped lift the death toll on New Zealand roads last month to 45 - 50 per cent more than in a typical month, in which 30 die and 300 survive crashes with serious injuries. In the 12 months to May 1, 384 people died on the roads, a similar number to the tally in the preceding 12 months.
Last year's provisional road toll of 377, similar to the 2017 figure, is a big jump from the 253 deaths in 2013, which was the lowest since 1950.
Associate Transport Minister Julie Anne Genter said last month's horrific road toll was heartbreaking.
"Particularly when you see the large number of very young people - adolescents and children - who have had their lives cut short or lost parents," she said.
However, the medical journal study also showed the toll left behind on the injured.
"What often gets overlooked is the enormous impact that serious injuries have on people's lives, sometimes the rest of their lives," she said.
The total social cost of fatal and injury vehicle crashes, including health care and lost earning potential, was estimated to be $4.8 billion in 2017.
"But, in fact, the true cost of that to people's lives is even higher," Genter said.
No-one has clear answers on why the road toll has increased so much after years of trending down. The Automobile Association says the only certainties are the rising population and that people on average are driving further each year.
The Government is spending $1.4 billion over three years on improving the safety of roads, such as by installing more median barriers, with the intention of greatly reducing serious crashes.
And Auckland Transport is planning to reduce speed limits on 10 per cent of the region's local roads.
Genter said improving road safety was a top priority for the Government as it focused on engineering solutions for safer roads, better education and tougher enforcement of the rules.
"We are working as fast as we can to turn the ship around," she said.
For a year, Karol Czuba, of Auckland University of Technology, and colleagues followed 112 adult victims of major trauma from the Middlemore and Auckland City hospitals. Fatal cases were excluded, as were patients in a vegetative state and those without the ability to give informed consent.
"The findings show that most study participants made a good recovery, but there was still a large group of people experiencing disability and not in paid employment at 12 months post-injury," the authors say in today's journal.
Rates of disability declined between the six-month and 12-month follow-ups.
At six months, 23 per cent were experiencing severe disability and this declined to 15 per cent at 12 months. Moderate disability declined from 37 per cent to 32 per cent. Those with a "good recovery" rose from 40 per cent at six months, to 53 per cent at 12 months.
At 12 months, 4 per cent had an extreme problem with mobility, and 30 per cent a moderate problem.
Looking only at the extreme problems, 2 per cent experienced this in self care, 2 per cent for usual activities, 1 per cent for pain, and 4 per cent for anxiety.
Regarding pain, 52 per cent had a moderate problem and 47 per cent no problem.
At 12 months, 55 per cent were in paid employment, up from 51 per cent at six months, but down from 69 per cent before the injury event.
Causes of injury in a study of survivors with major trauma
• 30.4% - Motor vehicle crash
• 25.9% - Vulnerable road users, including motorcyclists, cyclists and pedestrians
• 13.3% - Falls from 1m or higher
• 14.3% - Low falls, from less than 1m or standing
• 11.6% - Struck or collision, including from rugby, physical assault or stabbings
• 2.7% - Other
• 1.8% - Unknown
AA road safety spokesman Dylan Thomsen said, of the study: "It hammers home why we need to be doing so much better in terms of road safety."
"Travelling on the roads is probably the riskiest thing that people will do every day in their lives. The reality is that a lot of us tend to be too casual and blase about that because most of the time, most trips, people go from A to B perfectly fine."
Road quality and safety needed to be improved and speed limits needed to be reduced in some areas - although the AA opposed some of the reductions proposed for Auckland.
"We desperately need to be investing more in our roads," Thomsen said.
He said comparable countries to New Zealand had more motorways and high-quality divided highways. Our cars were on average also older, with fewer and inferior safety features.
But driver behaviour still needed to improve too, he said, noting that around a quarter of road deaths were of people not wearing a seatbelt at the time of their crash.
Drug and alcohol impairment and cellphone use remained a problem too and Thomsen pointed to a motion sensor on some newer smartphones that prevented their use in a moving vehicle.
The study's authors note that existing New Zealand surveillance systems do not include data on long-term outcomes of trauma survivors. Their study was to test the feasibility of such monitoring.
"The findings suggest that trauma registries are ideally placed to monitor long-term outcomes of trauma survivors, and can plan an important role in reducing the impact of burden associated with major trauma."