More die under lower booze limit

More Kiwis are driving drunk to the grave following the lowering of New Zealand’s alcohol limit.

Just-published findings show those who had been drinking, driving and then dying were drinking more. More drugs were also thrown into the deadly cocktail.

Forensic toxicologist Hilary Hamnett led the study, which was thought to be the first of its kind, looking at alcohol and drugs in dead drivers and motorcyclists.

Hamnett, who has previously worked at the Institute of Environmental Science and Research (ESR) in New Zealand, and the University of Glasgow in Scotland, looked at both countries, which lowered their drink-drive limits about the same time.

New Zealand’s law change – lowering the blood alcohol limit from 80 milligrams of alcohol per 100 millilitres of blood to 50mg – came into effect in December 2014.

In the year before, there were 30 road deaths with positive alcohol readings. The following year, there were 48. As a proportion of all road fatalities, those with alcohol involved rose from 11 per cent to 14 per cent, while alcohol plus drugs went from 12 to 18 per cent.

What Hamnett found was that Kiwis who died on the roads were more likely to have been drinking after the law change, while those that had been drinking had higher blood-alcohol readings, and were more likely to also have drugs in their systems.

The study, published in The Journal Of Forensic Sciences, did not speculate on why the law change would have such a counterintuitive result but Hamnett said it was ‘‘an interesting effect’’.

Broader social factors may have played a part, she said.

High-profile campaigns about the lowered limit ran in both countries but there was little evidence showing they had worked.

Acting road police national manager Virginia Welch said the findings had to be seen in context of other factors such as more road use, ‘‘exposure to higher-risk rural roads’’, and an overall increase in fatal accidents. ‘‘As a proportion of all fatal crashes, substanceinvolved fatal crashes have remained about the same.

‘‘There are many factors that contribute to [a] crash and many factors that lead to a fatal injury resulting. It would be naive to pick one out of the lot, while leaving all else to the side, and attributing to it a change in crash numbers.’’

New Zealand Initiative’s Sam Warburton said the small numbers in the survey and other factors, such as changing levels of enforcement, made it hard to say how much weight to give the findings.

The lowered drink-drive limit was ‘‘never going to be a silver bullet’’ and the Ministry of Transport had estimated it would result in only three fewer deaths per year. That was an ‘‘amount impossible to detect in data’’, he said.

Associate Transport Minister Julie Anne Genter was not ready to comment.