Driving impaired as a result of marijuana use is already against the law in all jurisdictions in Canada. It is likewise illegal everywhere else in the world and penalties can be harsh. Germany, for example drug tests anyone suspected of being under the influence of marijuana and drivers lose their driver’s license for one year if over the legal limit. New Zealand, however, has a much more enlightened approach and uses sobriety tests to determine actual impairment.
The Liberal Party’s stance is to provide police with more accurate tools to detect when motorists are under the influence of marijuana. With legalization, they recommend the federal government invest revenues to improve detection technology, training support and research regarding effects of cannabis use and intoxication.
They also recommend monitoring the results of Washington State’s proposal to establish presumptive levels of intoxication for THC concentration when a driver is arrested for suspicion of being under the influence. These have been set at 0.0 for drivers under the age of 21 and 5 nanograms/milliliter of blood for drivers aver 21. Washington’s Licensing Department will be able to revoke the driver’s license of a person who tests above the presumptive level of THC.

Sobriety tests are used to test for impairment from alcohol and increasingly marijuana: walk a straight line, balance with one foot raised in the air and with closed eyes, tilt head back and tell the policeman when 30 seconds have passed.
Getting drunk drivers off the road has been very successful with the advent of breathalyzers and random checks. Sobriety tests thus are rarely used much for alcohol. But it is harder now that roughly a third of all Americans are living in states that have decriminalized marijuana. To put is simply, proving that someone is driving stoned is a thornier problem than determining that a driver has had too much to drink. The body metabolizes pot in a way that makes it nearly impossible for scientists to agree on an appropriate legal limit for motor-vehicle operation, let alone come up with a toxicological test – like a simple breath-alcohol test – to measure how much a driver has inhaled. While it would seem obvious that driving while stoned is a bad idea, there isn’t enough evidence to prove it. Partly because of the roadblocks that years of illegality have posed, there is a dearth of scientific research on exactly how pot impairs driving and precisely how risky it is.

But it is no surprise that solving the problem is a priority for public officials, since there is evidence to suggest that driving high is a real danger. From 1999 to 2010, during a period of widespread decriminalization, the rate of drivers who died n crashes with marijuana in their system tripled, from 4% to 12%, according to a review of some 23,591 deaths in six states. The data does not show whether marijuana caused those crashes, but it does tell us that the number of drivers on the road with pot in their system has been rising fast and at the very lest correlates with mortality. It seems, at least for people at the wheel, there may be such a thing as being too mellow.
People tested 10 minutes after drinking or inhaling pot found that a blood concentration of THC of 13.1ug/L showed a level of weaving similar to drivers with a breath-alcohol concentration of 0.08% – the legal limit in most states. But, while alcohol increased the number of times a car left its lane and the speed of weaving, marijuana did not.

Adding to the screening controversy is a more basic debate. Scientists don’t even agree on the level of risk that marijuana poses to drivers who are high. Marijuana reduces motor coordination, slows reaction time and impairs decision making, according to NIDA. Studies have also suggested that marijuana may impair peripheral vision and the ability to concentrate, two vital skills at the wheel. And yet the body of scientific work on marijuana’s effect on motor-vehicle operation is small, and even then the results are all over the map. Some studies show that marijuana brings no extra risk of crash, while others show that it doubles the risk.
Alcohol, by contrast, increases by 13 times the risk of being killed for drivers ages 21 to 34.
Other nations are groping for legal and medical standards too. New Zealand uses a system that combines subjective signs of impairment with a zero-tolerance policy. If – and only if – a Kiwi driver fails the sobriety test, any amount of the drug in his blood is illegal. It’s an interesting idea that might help address cases in which a driver has used marijuana and alcohol in small amounts that would have little impact on their own but can be deeply intoxicating when combined.
Educating the public about the dangers of driving while high will help. Many Americans don’t know that smoking pot can impair their driving or that it is illegal to drive while high. Cops will have to rely on what may seem like primitive tells. In sobriety tests of stoned drivers, someone tracking a pencil across their face would struggle to keep an eye from wandering. Poor judges of time, most pot-impaired drivers would overestimate the passage of 30 seconds. The sobriety test is far from perfect, but for now, this is the only game in town.
Technology may come to the rescue. Canadians have created a breathalyzer that will detect marijuana use in the past two hours, a decent measure of impairment since pot’s effects are usually felt for about two to three hours after use. Technology will get more precise as legalization spurs research. We are on the cusp but have got a lot to learn.

In 1954, the breathalyzer was invented, and thanks to the activism from groups like Mothers Against Drunk Driving, it is now illegal in most of the world to drive with a blood alcohol level of 0.08% or above. Today toxicological results have mostly taken the place of subjective police testimony in court. The body’s relationship with alcohol is straightforward: as your blood-alcohol content rises, you get drunker, and as it declines, you sober up. While tolerance can alter the effects – at 0.08% blood-alcohol level, someone who rarely drinks is likely to seem drunker than a booze hound – the science says that at 0.08%, all people are impaired to some degree in the skills they need for safe driving.
With marijuana, it is not so simple. When you smoke pot, the psychoactive ingredient, THC, spreads throughout your body but leaves your body quickly as it is absorbed by your fatty tissues and brain, so that the amount of THC in the blood is not a good indicator of impairment. It is even possible to have less THC in your blood when the effects of pot are at their peak, usually about 10-30 minutes after your last puff. A recent study of 1,046 drivers in New Zealand who were killed in car accidents showed that, counterintuitively, drivers with lower levels of THC in their system were actually more likely to be responsible for a crash.
The way the body breaks down pot means that scientists have not been able to agree on a level of THC that causes impairment. In the 1980s, when the National Institute on Drug Abuse (NIDA), held a summit to do just that, the task proved too daunting. They had a room of toxicologists and nobody could come up with a number. Thirty years later, little has changed, leaving cops, prosecutors and users looking for measuring sticks. Society wants a black-and-white solution – the is, a number. If you are over it, you are impaired. It’s a little clearer with alcohol. With marijuana, it’s less clear. People are trying to fit marijuana into an alcohol box, and it doesn’t fit.
The body’s metabolism of marijuana also makes it harder to equip law-enforcement officers with a toxicological test that can give an accurate measure of impairment when the driver was on the road. As anyone who has smoked pot and taken a drug test for work knows, urine tests can detect marijuana for days – even weeks- after the last puff, especially if you are a frequent smoker. Fat stores THC, and as it trickles out of those tissues over the following days, it is converted into a metabolite that is detectable in urine. That makes urine tests a less than ideal measure of someone’s intoxication level when they were driving. THC disappears from blood quickly as it is absorbed in the brain, making blood tests a more reliable measure of recent use but not a great correlate of impairment. Blood tests are also invasive and logistically challenging – they can require a trip to the hospital or a telephonic search warrant from a judge, creating a lag between the time the driver was on the road and the blood test, leading cops to underestimate the amount of THC in the blood when the person was driving.
These challenges have made it hard for state legislators to write laws that are fair or effective. It is illegal to drive under the influence of marijuana in every state. The question is, how do your prove the driver was under the influence? A handful of states – Pennsylvania, Montana, Washington, Nevada, Ohio and Colorado – have set a numeric limit for THC in the blood, ranging from 1 nanogram (a billionth of a gram) of THC per millilitre of blood, to 5 nanograms. States are in a quandary: set the limit too high, like the 5-nanogram limit in Washington, and it may be a license to drive stoned. Set it too low – like the zero-tolerance policy for THC adopted in Wisconsin and 10 other states – and marijuana lobbyists will accuse you of convicting someone who might have last smoked a month ago. Nevada and Ohio have split the difference with a lower limit for THC found in blood and a higher one for metabolites found in urine, but such distinctions just underscore the confusion.

One aspect of this issue that has not been addressed is the difference in impairment (or the lack of) between the long-term habitual marijuana user and the occasional recreational user.
I would propose that there is no impairment in the chronic daily user and in fact, they a better driver under “the influence”. This is because marijuana is a stimulant rather than a depressant in the habitual user.
I am a 63-year-old retired medical doctor who has used marijuana heavily (although not when working) for several decades. I understand the metabolism and excretion of THC much more thoroughly than the ‘average citizen’. I also have a huge anecdotal experience of using marijuana and driving.
I am a notoriously poor sleeper and rarely sleep more than six hours per night. As a result I am chronically sleep-deprived. Now that I am retired, I frequently have a nap in the late morning to catch up on necessary sleep. However that was not possible when I worked. I doze off easily especially when doing physically inactive tasks like reading. As a result, I am not a great driver and would fall asleep at the wheel if it weren’t for marijuana (which I regularly use to drive safely).
My Anecdotal Experience Driving Under the Influence of Marijuana
1. For three years I had a girlfriend in Vancouver – 642 kilometers from my office door – 642 kilometers of British Columbia mountains that rarely took me more than 6 hours to drive. At least twice a month I would leave my office at the end of my workday around 5:30pm and drive to Vancouver to see her over the weekend. And I would smoke a lot of marijuana on the way. I never came close to falling asleep at the wheel. I used marijuana as a stimulant.
It is also well known that marijuana can improve concentration ability on one thing at a time. And when I was driving that concentration helped me be a better driver. The amnesia that is part of marijuana use also helps to forget all the miles one puts in.
There is no doubt that I would be long dead if I had not smoked marijuana for all these drives. None of them would have been possible without it. And to drive at these speeds (easily averaging over the speed limit) reinforces that idea that I was a safe driver. I never had an incident that could be described as endangering my safety.
2. I have fallen asleep at the wheel twice, both at times when I did not have marijuana available.
The first was in 2001 on a long drive from southern BC to Southern Utah (I have traveled to the desert southwest of the US thirty-three times to go on 2-week hiking trips and do not bring marijuana with me). At 80 miles per hour on cruise control, I fell asleep at the wheel, lost total control of the vehicle, went through the guardrail where I-15 crosses I-80 in Northern Utah, rolled my SUV six times and ended up on I-80. It was a terrible accident. The vehicle was totalled, all the windows were gone, and nothing remained in the vehicle but my girlfriend and myself. I was fine but she fractured her right humerus.
The second time was on the windy road along Slocan Lake in the West Kootenay. I was very tired, fighting sleep and foolishly continued driving. I eventually fell asleep at the wheel but because of slow speeds was saved by a guard rail. There was no damage to the vehicle or myself.

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I would like to think of myself as a full time traveler. I have been retired since 2006 and in that time have traveled every winter for four to seven months. The months that I am "home", are often also spent on the road, hiking or kayaking. I hope to present a website that describes my travel along with my hiking and sea kayaking experiences.
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