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Driving high ... and deaf

Doug Beazley, The Edmonton Sun, 27th July 2006

I hate repeating myself, normally. But some people don't listen. Especially when they're high.

I knew I was asking for trouble a few weeks back when I wrote a column about marijuana and driving. Apparently, the merest suggestion that marijuana makes you an impaired driver is controversial stuff in some circles.

"Wise up," writes a correspondent from Amsterdam (God, what a cliche).

"There are four studies conducted in the Netherlands, Canada and Australia that show cannabis not to be a danger on the highway, unless combined with alcohol."

"Experienced cannabis users perform as well as non-users in real world and laboratory tests under normal conditions," writes another reader. "They compensate and drive more cautiously."

"If marijuana impairs, I have to ask - how is it myself and many others I know smoke marijuana every single day and drive a taxi?" writes a man from B.C. "Marijuana does not impair you. It enhances the drive."

Note to travellers: if you find yourself hailing a cab outside the Victoria or Vancouver airports, I suggest you look closely at the cabbie's eyes. If they're bloodshot, take the bus.

What strikes me as odd about the pro-marijuana lobby's approach to driving impairment is that, not only are they reluctant to admit the weed impairs, many seem convinced it actually makes you a better driver.

You don't have to search far to find the reason. Several published studies suggest drivers under the influence of cannabis compensate for their impairment - by slowing down and leaving larger gaps between themselves and other traffic.

Here's Dr. Alison Smiley, a researcher at the University of Toronto, back in 2001: "The overall conclusion is that marijuana impairs driving performance, but not in the way that alcohol does. Marijuana use, on its own, tends to result in more cautious driving behaviour."

And if my granny had wheels, she'd be a wagon. Let's examine one of those studies which supposedly argues that marijuana impairment leads to more cautious driving. A study for a Dutch university, for example, dosed a small group of just 24 subjects and ran them through a series of driving tests, both with and without normal traffic.

First of all, that study did find evidence that marijuana impairs driving skills. It found an increase in "lateral position variability" - weaving in and out of the lane - among the weed smokers.

The study also found those under the effects of marijuana did leave large gaps between themselves and neighbouring traffic - but that those gaps got progressively smaller as the tests continued.

"Our explanation for this," the researchers concluded, "is that the subjects' caution was greatest the first time they undertook the test under the influence of (marijuana) and progressively less thereafter."

The researchers also found the effects of marijuana increased drivers' reaction times. Conclusion? Smoking weed makes you an impaired driver. You may be more cautious after taking your first toke, but that caution wears off.

"Remember, people used to believe drinking and driving was harmless," said Dr. Robert Mann, director of the Collaborative Program in Addiction Studies at the University of Toronto. "And there's evidence that people impaired by alcohol can compensate with their driving, to an extent.

"Cannabis affects your ability to track moving objects, to co-ordinate your motions to keep the car where it's supposed to be. It impairs your ability to multi-task, to pay attention to many factors at once. It affects memory." No question, booze kills more people behind the wheel than any other drug (it's more popular than marijuana, for a start).

But I can cite at least a half-dozen academic papers showing weed impairs psychomotor skills, reaction time, visual functions and attention - and puts the driver at a higher risk of killing or being killed.

So why do people drive high? Blame the legacy of anti-drug propaganda based on fantasy instead of facts.

After having been told, over the past century, that marijuana will blind you, render you impotent, make you insane (or stupid), lead you into heroin addiction, make boys grow breasts and turn innocent children into violent criminals, the current generation of weed smokers won't accept evidence for any drawbacks to marijuana consumption. They're not listening, because they've been lied to before.

In 2002-2003, about 15% of senior high school students in one Canadian survey reported driving under the influence of marijuana in the previous year. Is anyone surprised?

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