Study shows cannabis only impairs drivers for 30-60 minutes after smoking

Published Dec 26, 2019 02:00 p.m. ET

Now that smoking weed is entirely legal in many regions all over the world, it is important to consider the possible implications of the intoxicating substance from a few perspectives. The average quality of life for consumers due to health complications has always been at the forefront of this type of research, but now that it’s legal, specialists are studying the risks of driving high, and the results are a far cry from the hype that has led to a zero-tolerance policy right across Canada.

The law

Right now, smoking a joint is treated in a similar manner as alcohol in Canada, and with other major regions watching from afar and looking to follow suit, it is important to highlight the discrepancies with the current system. As of now, consumers are told to stay off of the roads after smoking weed, but the introduction of testing tool has many rightfully concerned, as the latest round of detection devices can give a driver a failing tests if they have smoked at any point in the last 24 hours, and in the case of some of the frequent users, even longer.

If you are caught behind the wheel of a motor vehicle within 24 hours of smoking weed, you risk a fine, demerit points and having your vehicle confiscated, depending on the situation at hand. The hope with these rules was that weary citizens might be more supportive of a bill that would legalize pot, but the research shows that the majority of those who would fail a roadside THC test, aren’t really impaired at all.

The research

The Center for Addiction and Mental Health, a Toronto based agency takes issue with Canada’s impaired driving laws surrounding THC, and to prove that there is a problem, they took voluntary study participants and allow them to get high, before tossing them into a lifelike driving simulator and testing their skills and impaired levels behind the wheel, without putting random passing people at risk in real life.


At the beginning of the study, researchers gave all the participants exactly 10 minutes to spark up a bowl, vaporizer, or a joint and get high. Since the people included were provided with the opportunity to gauge their own buzz, each one had a varying range of THC in their blood system ranging from 0 to 40 nanograms per milliliter, an amount that is ten times or more over the current limit for our currently used THC testing devices to deliver negative results.

The simulator placed each person into a 9-kilometer virtual stretch of road, with randomized stops, and issues, and retested their abilities over the course of the next 48 hours. What they found was that most of the participants that had consumed low doses of THC were not impaired at all, even immediately after smoking weed, and those that had indulged in high concentrations only displayed minor difficulty that lasted for less than 30 minutes afterward.

In conclusion

More research is necessary to solidify these results, but what we can learn from this vital information is that most people driving skills are not adversely impacted as long as they wait 30 minutes or more before driving home. The current laws that we as Canadians are expected to abide by, are in no way based on legitimate science, and merely another avenue for un-called for discrimination against a substance that is safer and impairs you for only moments, at the same time that we are allowed to enjoy a glass of wine, a well-known dangerous drug before the long haul home.

No increase in impaired driving rates since marijuana legalization


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