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No, Weed Doesn't Make You a Better Driver

"If you go back 40 to 50 years, people thought, I'm only going to have a drink or two because it relaxes me, so I'm a safer driver, a calmer driver."
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Photo by author

This post originally appeared on VICE Canada.

If you've been in a car, you've probably either driven high or been driven by someone who was. Unlike driving drunk, however, driving high doesn't seem to carry the same social stigma as its infamously deadly predecessor.

According to new research published by the Centre for Addiction and Mental Health (CAMH) Wednesday, the number of people smoking marijuana doubled from 8 percent to nearly 15 percent between 1996 and 2015. More worryingly, rates of impaired drivers who had THC in their system rose from 1.5 percent in 2010, to 3 percent in 2015.

If you're like any of my friends, you're probably thinking that the dangers of driving high are a myth (in fact, I know a few people who say it actually makes them better at driving). To clear the air, I asked Dr. Robert Mann, a senior researcher at CAMH and one of the leading Canadian experts studying the effects of driving while high, if smoking before driving is really that bad.

VICE: How does weed affect a person's ability to drive?

Dr. Robert Mann: I think the answer to that is simple: It affects the basic skills that are involved when driving safely. Marijuana causes, to quote [prior research], impairment in every performance area connected to safely driving a vehicle, such as tracking, motor skills, visual function, and attention. Break that down a bit more for me—how would I tell if a person in front of me on the road was driving high?
In the research we've done, there are a number of repeating characteristics that indicate a high driver: weaving on the road, slowing down and then speeding up, missing signs, and generally poor reaction time. It's very similar to being intoxicated. I'm 20, and the common argument I've heard—from both people my age and older—is that marijuana either doesn't affect some people's ability to drive, or actually improves it in some cases. Is there any truth to that?
Well, it's certainly true that marijuana is, by all means, a different drug than alcohol, so it may be true that the effects that marijuana has on driving skills may differ from that of alcohol. But that doesn't mean [the effects of marijuana] doesn't impair driving. Think about it this way: If someone is telling you that they can compensate for the impairing effects of the drug, then they're telling you the drug impairs them in the first place. It is interesting to go back in the scientific research, about 20 years ago. There were a couple of authoritative reviews of [scientific] literature that concluded that there wasn't good enough evidence to say that cannabis does have impairing effects. That got a lot of attention at the time and a lot of press [stating that] cannabis doesn't increase your collision risk. That may have really rooted itself into the public conscience, [despite] contradicting research since then. Do you think part of the reason why so many people don't see being high and driving as a problem is because cannabis, in modern culture at least, is starting to be widely viewed as a sort of miracle drug?
I don't necessarily know that's the reason. First of all, if there's something you do, you're going to try and rationalize it. That's a basic psychological process. But there's also a sincerity to it, I think. One of things that has been reported in the research is that people who [get high and drive] tend to slow down, or drive slower. Perhaps people interpret that as, Gosh, I'm driving slower, so I must be safer. The reality is that can actually contribute to accidents because you're not able to react as quickly as you should be to potential dangers on the road. If you go back 40 to 50 years, people thought, I'm only going to have a drink or two because it relaxes me, so I'm a safer driver, a calmer driver. Yet people still do abide by that rule in many ways. Blood alcohol levels, drink limits, and so on. How do you determine when someone is too high to drive?
That's a more difficult question. Literature generally suggests that between 3.5 and 5 nanograms/ML of THL in a person's blood is the point in which someone is equivalently impaired to that of being too drunk to drive—Colorado and Washington both have set 5 ng/ml as the legal limit. Breathalyzers have been a pretty reliable way of gauging sobriety for alcohol, but testing for THC levels is still a bit nuanced.
Somewhat. There is, of course, blood tests, but those are challenging to get, and are very rarely seen used in court. Research has shown that oral fluid testing technology are fairly effective at determining someone's level of impairment. What's worth noting is that, in the lab now, we're looking at the effects of alcohol and comparing that to the impairment effects of cannabis. We are also beginning a study on the interaction [the two drugs] have when used together while driving, because many fatal car accident victims actually end up having both cannabis and alcohol in their systems. What about other jobs—is it safe to do anything technical while high?
Well, I'd say that if it's a safety-sensitive job, you're only increasing the risk to yourself and others by being impaired. One profession in particular that this has been studied in is for pilots, and it's pretty standard across the board for a no-tolerance policy on substances with airline pilots. Surely, people drive high on prescriptions, such as opioid painkillers, all the time, but you rarely hear about that in the news.
Under the law, there's no distinction between illicit drugs and those that are prescribed. If someone is pulled over and they are impaired, they will face the same consequences as anybody else. It is not a defense, at least in Canada, to say that you were using the drug as prescribed. In the UK, there is a caveat in the law for that—if you can prove that, you were using the drug as instructed. Do you think car accidents will rise when marijuana is legalized?
I don't know. We have been helping to [advise the government task force for marijuana] on things that we feel are important to take into legalization, and one of those is that marijuana should be treated and regulated like alcohol. We have seen campaigns against drunk driving, about the dangers of smoking, do very well. With that said, we are also for legalization. The current prohibition process is clearly not working. Follow Jake Kivanc on Twitter.