Lower alcohol limit fails to stem road toll

More Kiwis are driving drunk to the grave following the lowering of the alcohol limit.

Just-published findings show that those who had been drinking, driving, then dying were drinking more than before and more drugs were thrown into the deadly cocktail. Forensic toxicologist Hilary Hamnett led the study which looked at alcohol and drugs in dead drivers and motorcyclists.

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

New Zealand lowered the blood alcohol limit from 80 milligrams of alcohol per 100 millilitres of blood to 50mg in December 2014.

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

Hamnett found that after the law change New Zealanders who died on the roads were more likely to have been drinking, they 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, on the phone from Britain, Hamnett said it was ‘‘an interesting effect’’.

Broader social factors might 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.

The one glimmer of hope in the study was seemingly unrelated the the lowered limit. Those who tested positive for drugs – but no alcohol – dropped after the law change. But if alcohol was also involved, the chances of drugs also being there increased.

Cannabis was the most popular drug, followed by prescription drugs, over the counter drugs, then opioids.

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 substance-involved fatal crashes have remained about the same,’’ she said.

‘‘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.’’

Road safety campaigner Clive Matthew-Wilson, editor of car review website Dog and Lemon, said the findings were unsurprising. ‘‘Lowering the drink-drive limit without restricting access to alcohol is like telling kids not to eat candy, then leaving them outside a candy store.’’