A new study will examine the impact kava drinking has on drivers, as one researcher claims the drink is growing more popular in New Zealand.

Dr Apo Aporosa of the University of Waikato said more than 20,000 people used kava on an average Friday or Saturday night in New Zealand.

He said many kava users were drinking 32 times more than pharmacologically recommended doses, and then driving.

But the drink's impact on driving was still largely uncharted territory.

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Dr Aporosa, a kava drinker himself, said when he drank more than the recommended amount, he was still able to speak, walk and communicate well.

"And I think I can drive. But can I really drive? Because there are lots of dope smokers out there who think they're good at driving too."

Dr Aporosa, a former police officer, said roadside breath-alcohol tests were ineffective at detecting kava.

"Many Saturday nights I go into checkpoints and blow into the bags and nothing shows up," he told NZME.

"You get very very relaxed. I've done roadside sobriety tests at 2 and 3 in the morning with kava users and they seem to react fairly well."

He said anecdotal evidence suggested kava was contributing to some car accidents.

Dr Aporosa, a Massey graduate of Fijian heritage now based in Hamilton, won funding from the Health Research Council (HRC) for the two-year study into the effects of kava on driving.

The HRC said the postdoctoral fellowship was worth $230,000.

Dr Aporosa's research would include having participants drink kava, then try out a driving simulator.

"The reason I wanted to do this research is that kava is critically important to us as a cultural icon. So this isn't an anti-kava thing. This is about a practice that we have within a contemporary, mobile society."

He said kava was increasingly popular among people who weren't Pacific Islanders, including Mormons and Muslims who generally did not drink alcohol.

Dr Aporosa has lambasted proposed bans on kava in Australia. He said although thousands of people died annually from smoking and alcohol, there'd not been one death anywhere on Earth in the past decade blamed solely on kava.

New Zealand Drug Foundation executive director Ross Bell said there was a dearth of research about kava's impact on driving.

"It's great that someone's looking into this issue.

"The research shows yes, it's an issue, but it's a very difficult issue to detect ... combining alcohol and kava seemed to be a problem in Fiji."

Dr Iris Wainiqolo discussed kava and drinking at the Symposium on Drugs and Driving last year.

She said the issue had received minimal attention.

NZME