Researchers have called for an overhaul of ACT drug-driving laws, after a new study revealed how long people are impaired for after using cannabis.
While cannabis use and possession in small amounts was legalised in the ACT in 2020, the drug has been known to be picked up in roadside drug tests as long as several days after being consumed.
However, a study undertaken by researchers at the University of Sydney revealed those who have taken cannabis would have a 'window of impairment' of between three to 10 hours.
It comes as new figures revealed more than half of all positive roadside drug tests conducted in the ACT since the drug laws came into effect in January 2020 were related to cannabis.
The study's co-author Iain McGregor said the findings, the first time a length of time of cannabis impairment has been revealed, could have serious repercussions for drug-driving laws in the ACT.
"Our legal frameworks probably need to catch up with that and, as with alcohol, focus on the interval when users are more of a risk to themselves and others," Professor McGregor said.
"Prosecution solely on the basis of the presence of THC in blood or saliva is manifestly unjust."
While drug-driving is still an offence in the ACT despite the softened stance on cannabis, the new research has called into question how long users are impaired for after using the drug and when they would be able to undertake tasks like driving.
ACT Policing figures have shown since the laws were enacted in January 2020, 921 positive roadside drug tests have been recorded, with 470 of those having THC - the intoxicating component of cannabis - involved.
Of the 470 positive results for THC, 41 per cent of those were recorded as only cannabis, with the rest being made up of THC mixed with a combination of other drugs such as MDMA or methamphetamine.
An ACT Policing spokesman said drug-driving offences have remained stable since the introduction of the new cannabis laws.
"ACT Policing has not identified any significant issues in implementing the ACT government's new cannabis laws," the spokesman said.
"Like alcohol, drugs impair your ability to drive and greatly increase your risk of being involved in a serious collision.
"ACT Policing strongly discourages drivers using any substance that impairs their ability to safely control a vehicle and then driving on a road in the ACT."
It is still an offence under current legislation to be driving with drugs such as cannabis in your system.
The ACT legalised possession of cannabis up to 50 grams in January 2020, and allowed residents to legally be able to grow two cannabis plants, up to four plants per household.
The University of Sydney report, based on analysis of 80 scientific studies, found those who smoked cannabis were impaired for a shorter amount of time compared to those who took THC orally.
The study's lead author Dr Danielle McCartney said the findings were a significant breakthrough.
"Unlike alcohol, where blood-alcohol concentration correlates with impairment, there has no been simple correlation between THC levels and impairment," Dr McCartney said.
"We found impairment subsides between a three- and 10-hour window, depending on the context [in] which the cannabis is consumed, and that gives us a measure of how long it takes to recover.
"THC is known to acutely impair driving and cognitive performance, but many users are unsure how long [it needs to be before] they can resume safety-sensitive tasks such as driving after cannabis consumption."
Dr McCartney said the new cannabis information would prove to be valuable for future legislation in the area.
"This is all about allowing people to make informed decisions and to develop public health advice that's evidence-based," she said.
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