Mixing weed, alcohol and driving: The 'unanswered question' in the cannabis referendum

By the end of this year it could be legal in New Zealand to smoke a joint at a party, which could raise an interesting dilemma. If you have a beer or two and a few puffs on a joint, will you be able to drive? 

Most Kiwis know the drink driving laws. If they find themselves at a party and they're planning to drive, generally people will only have one or two drinks. 

But what will the cannabis laws be, and do Kiwis realise the potentially deadly consequences of mixing the two substances with driving? 

These questions have been brought sharply into focus ahead of the cannabis referendum this year.

Last year the Government released a draft Cannabis Legalisation and Control Bill which Kiwis will vote on at the election. If passed, recreational cannabis would be made legal. 

The proposed law change includes a number of control measures such as a minimum purchase age of 20, a ban on marketing and advertising and controls on the potency of recreational cannabis being sold.

However, there are no details in the legislation around the legal limits for how much THC - the main psychoactive component in cannabis - someone can have in their system and drive. There are also no specific guidelines about how much of both alcohol and cannabis a person could have in their system and still drive. 

But mixing cannabis and alcohol, even small amounts, and driving can have severe consequences, said AA road safety spokesperson Dylan Thomsen. 

"This is a situation where one plus one actually equals a lot more than two. People don't realise that the combination of alcohol and cannabis... acts as a multiplier. 

"Combining even a small amount of alcohol with drugs is going to potentially mean that you are really, really impaired and shouldn't be driving.

"It will mean people are slower to react, are more likely to miss seeing something. If you have the right set of circumstances, those couple of seconds longer… they can make a huge difference in terms of whether you end up in a crash or not."

National's drug reform spokesperson Paula Bennett says it's an issue the Government needs to address before the referendum. 

"This is just one of a number of unanswered questions around what the legislation will mean for the normalisation of drug use, youth access, drugged driving and workplace health and safety," Bennett said. 

"We are very concerned about people mixing cannabis and alcohol and then driving. Mixing the two will result in further impairment while driving, and studies show the combination disproportionately lasts in your system."

Associate Transport Minister Julie Anne Genter is introducing a new law in 2021 giving police the right to conduct random roadside drug testing on drivers. 

Anyone who tests positive will receive a fine and be immediately suspended from driving for a minimum of 12 hours.

Criminal penalties may also be possible, depending on further blood tests. 

Genter said random testing would be happening regardless of the referendum result. 

She said testing will help deter, detect and prosecute drugged drivers.

"Cannabis prohibition clearly isn't working. Currently, the sale of cannabis is happening in the shadows of the black market, and the rate of drugged driving is getting worse.

"Legalising and regulating the sale of cannabis would allow the Government to focus on harm reduction by targeting resources to health treatments and education."

The Government said the draft cannabis referendum legislation does not include any changes to the current Land Transport Act. 

A second draft of the Bill will be released in the next few months, which will contain more detail. This will be the version of the Bill that is voted on in the referendum.

The proposed cannabis law includes:


  • a minimum purchase age of 20
  • a ban on marketing and advertising cannabis products
  • a requirement to include harm minimisation messaging on cannabis products
  • not allowing recreational cannabis to be consumed in public and only in licenced places
  • limiting the sale of recreational cannabis to physical stores
  • controls on the potency of recreational cannabis being sold
  • a state licencing regime for recreational cannabis controlled by the Government
Sign up to receive news updates

By entering your email address, you agree to our Terms of Use and Privacy Policy. Newshub and its affiliates may use your email address to provide updates/news, ads, and offers. To withdraw your consent or learn more about your rights, see the Privacy Policy.