New research suggests New Zealand's drug-driving epidemic may be worse than officials thought.
An online survey of 1200 Kiwi drug users shows one in four drove after taking cannabis in the last year, while 21 per cent admitted drink driving.
The Drug Foundation survey has top officials worried.
As police prepare to enforce new drug-driving tests from December, Transport Minister Steven Joyce said the problem "may be bigger than previously known".
"Police, I think, are keen to get the enforcement under way," he said. "If you're impaired while driving you're then tested for drugs. If you fail that test then you are charged."
Drug Foundation executive director Ross Bell was surprised by the survey results.
More than half of respondents said taking cannabis did not affect their driving ability and more than 16 per cent said it improved it.
"That has real, obvious implications for the road safety messages we need to get out to people who use drugs."
Fourteen per cent of respondents said they had used other drugs, most commonly methamphetamine, methadone and morphine, while driving.
But Bell said the new police tests may not solve the problem.
He described them as "dodgy American-style field impairment tests where they get drivers to walk in a straight line and those kinds of things".
"It just doesn't have the same degree of rigour that we would want in a drug-testing regime."
Environmental Science and Research is working on a long-term study analysing blood samples from most driver deaths in New Zealand.
Preliminary results show 40 per cent of drivers killed between 2004 and 2006 had used alcohol, cannabis or both before their death.
Thirty per cent of drivers who used cannabis and died in a motor vehicle accident were likely to have smoked within three hours of driving.
But, without the technology to detect drug users quickly, the number of people convicted of drug-driving is low.
Provisional police data shows 69 people were charged with driving under the influence of a drug last year, compared with 60 in 2006 and 84 in 2007.
Only one person was charged with causing death while under the influence of a drug.
The size of the problem is no surprise to Taranaki mother-of-three Eileen Tamati.
Her husband Kent Martin, 36, was killed last year by a driver high on a cocktail of cannabis and methadone.
"Sometimes I contemplate, just driving home, about how easy it would be for somebody to swerve off the road and hit me head-on," she said.
"For Kent it was just a second and that's all it took."
Martin was killed when Richard Martin Burgess shunted a vehicle waiting at an intersection into the path of his oncoming car.
Tamati, whose mother was killed by a drink-driver when she was 8, was five months pregnant at the time.
She says the subsequent birth of a son, now 14 months, had helped her cope with her husband's death. "It's made us as a family a lot stronger."
Burgess was sentenced to two years in prison, suspended from driving for five years and ordered to pay $2000 in reparation.
Tamati, a 37-year-old physical education teacher, called for education campaigns to target people before they started driving and harsher penalties for offenders.
"I know a lot of people that do it and I've asked them on various occasions how they don't think that they could be affected by it.
"It's a little bit of small-mindedness, a little bit of habit, and the thought, 'It's not going to happen to me'.
"But why would you risk that? Why risk taking a father away from his unborn child?"
Foundation for Alcohol and Drug Education (Fade) director Colin Bramfitt believes Ministry of Transport plans for education and roadside tests are the best first step in addressing the problem.
"It's not a quick-fix thing. Driving is one of the most dangerous things that anybody will ever do in their lives, not only to you but to other people."
* Drugged driving
Results from Drug Driving in New Zealand: A survey of community
attitudes, experience and understanding by the Drug Foundation.
Out of 1200 online participants:
21.4% admitted drink driving in the last year.
24.5% admitted driving after taking cannabis in the last year.
11.6% reported driving under the influence of multiple substances
in the past year.
78.6% of cannabis drivers felt their driving did not change for
better or worse under the influence of the drug.
76.5% of respondents "totally agreed" or "somewhat agreed" that drug
driving was a significant road safety issue in New Zealand.
70.5% of participants "totally agreed" or "somewhat agreed" that
random roadside drug testing would improve road safety.