Impaired Driving and Cannabis – Victoria Times Colonist


One study found that the combination of cannabis and alcohol impairs driving ability to a much greater extent than either substance used alone.

As the recent court case involving a Central Saanich man who punched and killed a woman and seriously injured her sister nearly four years ago unfolds in Victoria, new findings about how cannabis affects driving abilities people have also been published.

In the Supreme Court of British Columbia, Anthony Thomas pleaded not guilty to six driving offences, including impaired driving and dangerous driving which caused the death of Kim Ward, 51, on August 27, 2018, and the impaired driving and dangerous driving causing bodily harm to his sister, Tracy Ward.

During the trial, an expert toxicologist testified that a blood sample taken from Thomas shortly after the collision contained methamphetamine at a level consistent with a moderate to high single acute dose. The possible effects of the use of the drug on the ability to drive have been described.

Cannabis is not one of the drugs named in the trial. But the case raised the issue of drug-impaired driving, with the judge’s verdict yet to come.

Reviewing some of the cannabis studies published recently shows some of the progress made by Canadian research on the same question for marijuana.

One of the studies shows that the combination of cannabis and alcohol impairs driving performance to a much greater extent than either substance used alone. Canadian researchers analyzed the results of 57 separate studies, representing approximately 1,725 ​​participants. They found that cannabis and alcohol each produce different types of misbehaviour, but the effects of the two substances combined create even more dangerous levels of impairment.

Cannabis alone has been found to affect driving performance similarly to low blood alcohol levels. This reduces the ability of drivers to stay in their lane, although drivers under the influence of cannabis tend to slow down their driving speed.

In contrast, alcohol consumption alone increases driving speed and affects many other driving performance indicators. These include increased crash count, weaving, lane departure, speed and speed variability, and reduced response times.

However, when combined, cannabis and alcohol impair drivers’ ability to maintain their lane position more than either substance alone.

In another study, published in October, researchers from the University of Victoria and their American counterparts showed that between 2000 and 2018, the percentage of deaths in car accidents in the United States involving cannabis had doubled, and that the percentage of deaths involving both cannabis and alcohol had more than doubled. The researchers also found that people who died in crashes involving cannabis were 50% more likely to also have alcohol in their system.

The findings are supported by a University of British Columbia study in January that showed THC is detected in twice as many injured drivers in Canada since cannabis was legalized here.

THC is the compound in marijuana that makes you feel high.

Before cannabis legalization, 3.8% of drivers had blood THC levels above the Canadian legal driving limit of 2 nanograms/ml. The percentage increased to 8.6% after legalization. The proportion of drivers with THC concentrations above 5 nanograms/ml more than tripled to 3.5% after legalization.

THC levels can reach 100 nanograms or more within 15 minutes of smoking. It can take up to four hours for levels to return to the legal limit.

In an earlier study, the same researchers found little evidence that THC concentrations below 5 nanograms/ml increase the risk of traffic accidents. However, they found evidence that higher THC levels – above 5 nanograms/ml – increase this risk.

The problem, of course, is that the legalization of marijuana has been accelerated in Canada for political purposes, not to support public health and safety. Because cannabis has long been classified as an illegal substance, little research has been done on how it affects the brain, what levels of THC in the blood indicate impairment, or how long the compound persists in the body. body. There were also no tools available at the time to measure THC blood levels suitable for conducting roadside sobriety tests.

Contrary to the mantra we heard last month regarding COVID safety measures in British Columbia, the cannabis legalization process was not based on science or evidence.

And now, in the impersonal language of statistics and analysis provided by researchers, we are beginning to see the impacts of the rapid legalization of cannabis.

Just like Kim and Tracy Ward are people with families, friends, co-workers and clients, these cannabis statistics also represent real people.

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