Groundbreaking research into drug driving shows people under the influence of cannabis are more likely to drift into the wrong lane.
Swinburne University has a purpose-built simulator which mirrors driving that is used in testing.
Professor Con Stough said the university was interested in studying the impacts of illicit drugs on driving when they started the research.
"At the time cannabis use was high and we were concerned that there was not much high quality research that could inform the public about whether various drugs could impair driving," Professor Stough said.
"Reducing car accidents and road deaths was an important aim of our research."
Professor Stough said studies were conducted with participants taking either a quantity of a drug or a placebo.
"The studies are also double blind so that the participant nor the experimenter know which treatment the participant is being given," he said.
"Most of our studies are also cross-over studies, so one week the participant will be given the drug or placebo and tested on the driving simulator and the next week the participant will be given the other treatment."
Professor Stough said researchers compared performance on the simulator, cognitive tests, visual processes and other tasks.
He said the driving simulator had authentic controls and participants take part in various driving scenarios.
"Usually the participant will drive the simulator for a long period of time and we will measure a range of measures such as speed, braking and safety variables," Professor Stough said.
He said the university had run dozens of studies over the past decade on the effects of cannabis, methamphetamine, dexamphetamine, ketamine, alcohol, benzodiazepines and combinations of the drugs.
"We've even run the simulator with some herbal drugs such as kava," Professor Stough said.
He said the research showed that most illicit drugs impaired driving.
However, they do not all impair driving or cognitive ability in the same way.
"Cannabis increases lane weaving and slows reaction time, whereas amphetamines narrow attention, impairing peripheral processing from our environment."
Professor Stough said even low doses of alcohol impaired driving.
He said drink driving resulted in large and observable impacts.
"Even low levels of alcohol can be impairing and cause dangerous driving," Professor Stough said.
He said more research needed to be done to assess the impacts of a combination of drugs and alcohol and the effects of a number of pharmaceutical drugs.
The Standard reported last weekpolice were concerned about the growing number of people testing positive to drugs while driving.
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