Research shows that testing a driver’s blood level for THC isn’t a very good way to judge if someone should be behind the wheel. Unfortunately, there’s not a clear link between how much THC is in the blood and how much a person is impaired, but that’s the measure the federal government embraced as it prepared for legalization in 2018. The Canadian government created three new driving offences based on how much THC is in a driver’s bloodstream.
Some believe that these levels of THC in the blood are arbitrary lines, and that further investigation into laws around cannabis in Canada must be done.
Why are blood tests an ineffective way to determine driver impairment?
If someone smokes cannabis all weekend, but is sober by Sunday evening, then by Monday morning they would be considered fit to drive. However, under these laws, the amount of THC that would still be present in someone’s bloodstream at that time could be enough to get them into serious trouble.
Determining whether a cannabis user is impaired while driving isn’t so simple. A habitual smoker can have THC in their system and not be impaired to drive. In California, the highway patrol relies on field sobriety tests rather than blood tests.
Are field sobriety tests better than blood tests for cannabis?
Sobriety tests are really good for alcohol, obviously. They also are good at getting psychophysiological responses, like a person staggering while walking and so forth. However, the effects of cannabis are generally more cognitive than alcohol, so researchers are incorporating other tests to try to detect impairment. These additional activities are testing factors such as memory, attention, and motor control.
How does smoking cannabis affect my driving?
Researchers conducted a study using a driving simulator with common driving decisions to help test the question of how much smoking weed impacts your driving. The driving decisions included turning left with oncoming traffic, and facing the yellow light dilemma (should I go through or stop?). Participants of the study went through a few test drives and then received a joint. The joints all had different doses, from no THC to high THC. Researchers wanted to learn how the dose affected driving as well as the effect a few hours later.
According to this study, cannabis does have an impact on driving. When people do challenging tasks they don’t complete the task as successfully as when they were sober. They tend to swerve more on the road and take longer to brake.
How much THC can be in my bloodstream in Canada while driving?
There are three levels of impairment that the Canadian government has defined for the purposes of charging a driver with driving under the influence. Two of levels are as follows: if you have a reading between two and five nanograms of THC you’re subject to what’s called the summary conviction, which is a lesser criminal offense. If it’s over five nanograms of THC, you’re subject to an indictable offense.
How does cannabis affect my driving?
As mentioned before, cannabis does impair performance. The acute effects are slow reaction time, reduced attention, and divided attention. At higher levels it reduces psycho-motor-coordination in some studies (though, not all).
Studies have shown that driving under the influence of cannabis can lead to increasing the distance driving behind cars and reduction of average speed. The intensity of effects in adults change vary on whether you smoke or ingest cannabis, so the severity of these effects are varied as well.
Do people who are stoned think they drive better?
When people drive under the influence of cannabis, close to 40% of those surveyed asserted that they drive more cautiously. 30% said they drive normally. Only a small percentage said that they drive more recklessly. When asked about cocaine use, these numbers reversed. However, it is important to note that cannabis is not a clear-headed drug. It impairs your cognitive ability to a degree that means you should absolutely not drive or operate heavy machinery, no matter how sober you might feel.
One of the reasons why it’s important not to drive even when you believe you aren’t impaired is because of subjective feelings of being high. Someone who consumes cannabis regularly will feel less stoned than someone who only smokes weed occasionally. That means that a small amount of weed will make an inexperienced smoker significantly more impaired. An experienced smoker, however, is not more sober – they are just more familiar with the state, and have a tolerance to the substance.
