Cannabis and Driving
Queensland, Australia: Patients who consume botanical cannabis over extended periods do not exhibit significant changes in their simulated driving performance, according to data published in the Journal of Safety Research.
Australian researchers assessed patients’ simulated driving performance at baseline and 45 minutes after they vaporized prescribed doses of cannabis flowers. (Under Australian law, physicians may authorize cannabis products to patients unresponsive to conventional prescription treatments.)
“After vaporizing one dose of their prescribed cannabis flower, participants exhibited no significant changes in performance on any of the video-based tasks (hazard perception skill, gap acceptance, following distance or speed) compared to baseline,” investigators reported.
The study’s authors concluded, “The findings … suggest that a dose of vaporized cannabis (consumed in accordance with prescription) may not affect hazard perception ability or driving-related risk-taking behavior among medicinal cannabis patients.”
The study’s findings are consistent with those of several others determining that daily cannabis consumers, and patients especially, exhibit tolerance to many of cannabis’ psychomotor-influencing effects. According to the findings of a literature review published in the journal of the German Medical Association, “Patients who take cannabinoids at a constant dosage over an extensive period of time often develop tolerance to the impairment of psychomotor performance, so that they can drive vehicles safely.”
Full text of the study, “The acute effects of vaporized cannabis on drivers’ hazard perception and risk-taking behaviors in medicinal patients: A within-subjects experiment,” appears in the Journal of Safety Research. Additional information is available in the NORML Fact Sheet, ‘Marijuana and Psychomotor Performance.’
Article from – NORMAL
Driving Under the Influence of Cannabis: Impact of Combining Toxicology Testing with Field Sobriety Tests
Clinical Chemistry, Volume 69, Issue 7, July 2023, Pages 724–733,
https://doi.org/10.1093/clinchem/hvad054
https://doi.org/10.1093/clinchem/hvad054
Published: 25 May 2023
Abstract
Background
Cannabis is increasingly used both medically and recreationally. With widespread use, there is growing concern about how to identify cannabis-impaired drivers.
Methods
A placebo-controlled randomized double-blinded protocol was conducted to study the effects of cannabis on driving performance. One hundred ninety-one participants were randomized to smoke ad libitum a cannabis cigarette containing placebo or delta-9-tetrahydrocannabinol (THC) (5.9% or 13.4%). Blood, oral fluid (OF), and breath samples were collected along with longitudinal driving performance on a simulator (standard deviation of lateral position [SDLP] and car following [coherence]) over a 5-hour period. Law enforcement officers performed field sobriety tests (FSTs) to determine if participants were impaired.
Results
There was no relationship between THC concentrations measured in blood, OF, or breath and SDLP or coherence at any of the timepoints studied (P > 0.05). FSTs were significant (P < 0.05) for classifying participants into the THC group vs the placebo group up to 188 minutes after smoking. Seventy-one minutes after smoking, FSTs classified 81% of the participants who received active drug as being impaired. However, 49% of participants who smoked placebo (controls) were also deemed impaired at this same timepoint. Combining a 2 ng/mL THC cutoff in OF with positive findings on FSTs reduced the number of controls classified as impaired to zero, 86 minutes after smoking the placebo.
Conclusions
Requiring a positive toxicology result in addition to the FST observations substantially improved the classification accuracy regarding possible driving under the influence of THC by decreasing the percentage of controls classified as impaired.
PDF – hvad054
Article – Driving Under the Influence of Cannabis
Regular Cannabis Users Drive As Safely As Sober People, New Study Suggests
September 1, 2021 – by Chris Moore
Researchers found that weed impaired driving performance in occasional pot users, but daily stoners were able to drive as safely as sober drivers.
Regular cannabis users are able to drive as safely as sober people, even while stoned, according to a new study published in the Accident Analysis and Prevention journal.
To investigate the potential risks of cannabis-impaired driving, a team of researchers affiliated with the University of Colorado recruited 85 adults between the ages of 25 and 45 to participate in a simulated driving study. The subject pool included 31 subjects who reported using cannabis every day, 24 who said they got high one to two times a week, and 30 people who did not use cannabis at all.
Each subject performed two separate tests using a car-based driving simulator with a 45 minute break in between each session. During the break, each cannabis-using subject was given 15 minutes to get as high as they wanted using flower that they purchased themselves. Researchers asked participants to bring bud with 15 to 30 percent THC content, but did not impose any other limitations on what kind of weed could be used. The control group of non-users remained sober for both of the driving tests.
Using the MiniSim™ National Advanced Driving Simulator, researchers obtained two separate measures of driving performance in simulated urban driving scenarios. The simulator recorded data on the standard deviation of lateral placement (SDLP), which measures a driver’s ability to safely remain in their lane on straight road segments and turns. Researchers also kept track of whether drivers drove faster or slower than the speed limits posted in the simulation.
Researchers found that the occasional pot users performed significantly worse on the SDLP test after getting high, which suggests that weed could indeed be interfering with their ability to drive safely. But experienced, daily users were able to drive as safely as the sober control group. Occasional users also drove slightly faster than the posted speed limit when they were stoned, but not fast enough to be statistically significant. On the other hand, daily pot users drove significantly slower than the speed limit after getting high.
“We observed a decrement in driving performance assessed by SDLP after acute cannabis smoking that was statistically significant only in the occasional users in comparison to the nonusers,” the study authors concluded. “Daily users drove slower after cannabis use as compared to the occasional use group and non-users.”
This study brings new insight to a growing field of research on cannabis-impaired driving. Anti-legalization groups and law enforcement officials have constantly warned that adult-use legalization will lead to an increase in pot-related traffic accidents, but the data so far suggests that this is not the case. Several recent research studies have found that it is more dangerous to drive under the influence of prescription pills than weed, and that THC alone does not increase the risk of accidents.
This research also clearly highlights the fact that THC blood tests cannot effectively predict whether or not a driver is too stoned to drive safely. Many US states and Canadian provinces have imposed per se THC limits for drivers, and anyone caught exceeding that limit can be fined or even have their license suspended.
The present study reports that the daily cannabis users had six times as much THC in their blood as occasional users – but in this case, the users with higher THC blood levels were actually driving more safely than those with lower levels. Researchers have also found that past-day weed smoking can cause a person to test over the limit for THC, even though they are completely sober at the time of the test.
Story from MerryJane.com
Cannabis and driving study casts doubt on zero-tolerance limits for THC
People using a driving simulator showed no signs of impairment a day after they smoked cannabis, though they still tested positive for THC, its main psychoactive component, a recently-published paper says.
The research has implications for laws and workplace rules that require no trace of THC, which Scott Macdonald, a retired professor at the University of Victoria, calls “not scientific.”
“I consider it one of the biggest myths about cannabis, that there are 24-hour hangover effects that are measurable,” he said. “When people smoke cannabis, they’re only impaired for a short, short period of time. You could have THC in your bloodstream, but you’re not a danger.”
Researchers at the Toronto-based Centre for Addiction and Mental Health gave participants 10 minutes to smoke cannabis to a level they chose, then tested them in a driving simulator.
Because they were allowed to control their own consumption, THC blood levels in the group varied. They ranged from zero to 42 nanograms per millilitre, which would be nearly 10 times the legal limit to drive.
READ MORE: How long does cannabis stay in your system?
The driving simulator’s scenario involved a nine-kilometre drive on a stretch of rural highway signed at 80 km/h, with a few simple problems to solve, such as a slow-moving vehicle.
Immediately after smoking, the THC group showed signs of impairment, centring the imaginary car poorly in its lane and driving inappropriately slowly.
But in further tests 24 and 48 hours later, they still had detectable levels of THC, but performed normally in the driving simulator.
“We found significant evidence of difference in driver behaviour, heart rate and self-reported drug effects 30 minutes after smoking cannabis, but … we found little evidence to support residual effects,” the authors wrote.
The study shows that similarly to alcohol, cannabis impairment disappears within a day of consumption at most, if not much earlier.
However, THC can keep showing up on tests long after any impairment has ended — unlike alcohol, which would stop being detectable as impairment went away.
“The biological tests are not useful for identifying people that represent a safety risk,” Macdonald says. “What we’re left with is behavioural symptoms. We’re still working on developing tests to assess whether an individual who consumes cannabis is a safety risk. It’s hard to do.
“Cannabis is not in the same class as alcohol, in terms of safety risk. Alcohol is much, much worse.”
Several provinces forbid young or new drivers from having any detectable levels of THC.
In Ontario, for example, drivers violating a zero-tolerance rule for THC face a three-day licence suspension, $250 fine and $281 licence reinstatement fee for the first offence. Penalties increase for repeat offenders.
Saskatchewan took what may be Canada’s strictest approach: new drivers in the province with any level at all of THC face a 60-day licence suspension, a three-day vehicle seizure and four demerit points.
Ontario’s transport ministry defends the policy.
Several provinces forbid young or new drivers from having any detectable levels of THC.
In Ontario, for example, drivers violating a zero-tolerance rule for THC face a three-day licence suspension, $250 fine and $281 licence reinstatement fee for the first offence. Penalties increase for repeat offenders.
Saskatchewan took what may be Canada’s strictest approach: new drivers in the province with any level at all of THC face a 60-day licence suspension, a three-day vehicle seizure and four demerit points.
Ontario’s transport ministry defends the policy.
“I think [28-day bans] are excessive and not scientifically based, especially now that cannabis is legal,” Macdonald says. “If cannabis was illegal, I could see it from that perspective. It’s not scientifically based in terms of them being a risk for the public if they’ve used cannabis in the last 28 days.”
Toronto police are open to revisiting the 28-day ban, spokesperson Const. Victor Kwong wrote in an e-mail.
“(The rule) was made thoughtfully and based on sound advice and evidence, considering the critical role members play in ensuring a safe workplace and a safe community. We will continue to research and explore this procedure. If at any time there is new science or research to cause us to re-evaluate our processes, we will do so.”
A B.C. labour arbitrator recently ruled against TransLink, the Vancouver-area transit authority, over its handling of an employee’s positive test for THC.
David Solomon, a train attendant, was forced to undergo drug tests twice a month for a year, despite a doctor’s opinion that his cannabis use wasn’t a problem. Solomon had to call the testing service daily to find out whether he was going to have a test that day or not, and go to a lab to be tested if the answer was yes.
The military allows cannabis use at some times for some members, depending on their jobs. Some, like divers, aircrew, members of submarine crews and drone operators, have a 28-day prohibition similar to the more restrictive police forces.
“Many jobs — typically those which are safety sensitive — have adopted a zero tolerance policy, but as cannabis becomes more integrated into society, we’re going to need to consider policies that are reflective of this change and embrace a better understanding of cannabis and its effects,” Valleriani wrote.
“Some jobs require drug and alcohol tests as a condition of employment, but it begs the question of how workplaces can manage the risk of impairment without an accurate measure of it.”
The study was published this week in the Journal of Drug and Alcohol Dependence. Macdonald was not involved with it.
During the study, a placebo group was given joints with no THC to smoke, but it turned out that participants were well aware of whether they had consumed THC or not, with over 90 per cent in both groups accurately saying what group they were in.
When they were asked whether they would be comfortable driving a real car, 80 per cent of the placebo group said they would, as opposed to under 30 per cent in the THC group.
“It has the biggest sample size of any sample that I know of,” Macdonald said of the study’s 91 participants.
CAMH and Health Canada, where the study’s lead author works, did not make anybody available for an interview.
Story From Global News
What police are getting wrong about pot-impaired driving
Marijuana Users Are Safer Drivers Than Non-Marijuana Users, New Study Shows
A new study released by United States auto insurance quote provider 4AutoInsuranceQuote.com shows that statistically speaking, marijuana users are safer drivers than non-marijuana users.
NEW YORK (PRWEB) APRIL 06, 2012
In a recent study, 4AutoinsuranceQuote.com, a national quote provider for online car insurance quotes, cites a strong correlation between traffic-related accidents and marijuana use. The study, which looks at statistics regarding accidents, traffic violations, and insurance prices, seeks to dispel the thought that “driving while stoned” is dangerous.
In the study, 4AutoInsuranceQuote.com points out that the only significant effect that marijuana has on operating a motor vehicle is slower driving. 4AutoInsuranceQuote.com says, while referencing a study by the US National Highway Transportation Safety Administration (NHTSA), that driving slower “is arguably a positive thing” and that driving under the influence of marijuana “might even make you a safer driver.” A similar study by the NHTSA shows that drivers with THC (the active ingredient in marijuana) in their system have accident responsibility rates below that of drug free drivers.
In fact, a recent study shows that use of medical marijuana has caused traffic related fatalities to drop by up to nine percent in states that have legalized its use. This study, titled “Medical Marijuana Laws, Traffic Fatalities, and Alcohol Consumption”, conducted by Mark Anderson and Daniel Rees in November 2011, shows that increased marijuana use amongst adults has decreased alcohol related traffic deaths in said states. This study provides solid evidence that marijuana is not only a safe substitute for alcohol, but it also makes for more safer drivers.
“Marijuana users often say that when they are high, they feel like they are driving 80 miles per hour but actually are only going 30 miles per hour,” 4AutoInsuranceQuote.com CEO James Shaffer says, “when somebody is drunk driving, on the other hand, they often feel like they are driving 30 miles per hour but are actually driving 80 miles per hour. This is what makes alcohol dangerous behind the wheel, and marijuana safe.”
As an auto insurance quote provider, 4autoinsurancequote.com says that marijuana use can also have an indirect effect on insurance rates. Because of the correlation between marijuana use and accident responsibility rates, they say, marijuana users, as a whole, can expect to see lower insurance rates than non-marijuana users.
“The hypocrisy of it all is that if you get caught driving under the influence of marijuana, you will be fined and perhaps thrown into jail. Whats worse is that your insurance rates will definitely increase due to the traffic violation,” says Mr. Shaffer, “What law enforcement agencies and insurers do not understand is that driving while high is actually a safe activity. I guess the key to safer driving is to use marijuana, but to do it under-wraps.”
4AutoInsuranceQuote.com is an auto insurance quote provider operating out of Manhattan, NY. In business since 2008, they offer free insurance quotes online to United States users. In addition, 4AutoInsuranceQuote.com releases reports and studies on the automobile and insurance industries.
Reasons Why Marijuana Users Are Safe Drivers
Driving while intoxicated is a well known way to cause an accident on the road. Although not as common, you can be charged with that offense for more than just drinking alcohol. It also includes anything else that causes impairment, such as drugs (whether they are legal ones or not), including marijuana.
However, 20 years of study has concluded that marijuana smokers may actually be getting a bad rap and that they may actually have fewer accidents than other drivers. There have been several studies done over the past 20 years and every one of them has revealed that using marijuana actually has a very minor, if any, effect on the ability of a person to drive a car or other vehicle.
Marijuana, Alcohol users Use Products Differently
Research studies showed that if a comparison was done between how drivers who had been drinking alcohol and those who had been using marijuana, it showed that the pot users were in fewer crashes.
Why is this so?
Researchers believe it is because of the way people consume the two products, as alcohol drinkers usually do their drinking out in public and then try to drive home, while pot smokers usually smoke at home and don’t try to drive, meaning fewer are involved in driving accidents in the first place.
Research also shows that while drunk drivers usually drive faster and don’t understand that their driving skills are messed up, the drivers that have been smoking marijuana actually tend to drive slower and stay away from risky behavior.
These and other tests on marijuana smoking and driving were done in different places all over the world, including Canada, Australia, the Netherlands, the United States, and the UK with the following results:
Results of Major Studies on Marijuana and Driving
The research that has been done on this phenomenon of marijuana smoking and driving has shown some interesting results:
Research studies in the Netherlands at the Dutch Institute for Road Safety Research that drivers with blood alcohol rates of .5 percent up to .8 percent had accidents five times more than other drivers, and if it was higher amounts of alcohol, the results were accidents happening up to 15 times more often. But, the marijuana smokers actually showed these drivers posed NO risk at all!
Top 10 Reasons Marijuana Users Are Safer Drivers
When you combine all of the main results of these two decades worth of scientific research studies, the following 10 reasons marijuana drivers are safer than drunk drivers comes out like this:
1. Drivers who had been using marijuana were found to drive slower, according to a 1983 study done by U.S. National Highway Transportation Safety Administration (NHTSA). This was seen as a factor in their favour, since drivers who drank alcohol usually drove faster and that is part of the reason they had accidents.
2. Marijuana users were able to drive straight and not have any trouble staying in their own lanes when driving on the highway, according to a NHTSA done in 1993 in the Netherlands. The study determined also that the use of marijuana had very little affect on the person’s overall driving ability.
3. Drivers who had smoked marijuana were shown to be less likely to try to pass other cars and to drive at a consistent speed, according to a University of Adelaide study done in Australia. The study showed no danger unless the drivers had also been drinking alcohol.
4. Drivers high on marijuana were also shown to be less likely to drive in a reckless fashion, according to a study done in 2000 in the UK by the UK Transport Research Lab. The study was done using driver on driving simulators over a period of a month and was actually undertaken to show that pot was a cause for impairment, but instead it showed the opposite and confirmed that these drivers were actually much safer than some of the other drivers on the road.
5. States that allow the legal use of marijuana for medical reasons are noticing less traffic fatalities; for instance, in Colorado and Montana there has been a nine percent drop in traffic fatalities and a five percent drop in beer sales.
The conclusion was that using marijuana actually has helped save lives! Medical marijuana is allowed in 16 states in the U.S.
6. Low doses of marijuana in a person’s system was found by tests in Canada in 2002 to have little effect on a person’s ability to drive a car, and that these drivers were in much fewer car crashes than alcohol drinkers.
7. Most marijuana smokers have fewer crashes because they don’t even drive in the first place and just stay home thus concluded more than one of these tests on pot smoking and driving.
8. Marijuana smokers are thought to be more sober drivers. Traffic information from 13 states where medical marijuana is legal showed that these drivers were actually safer and more careful than many other drivers on the road.
These studies were confirmed by the University of Colorado and the Montana State University when they compared a relationship between legal marijuana use and deaths in traffic accidents in those states. The studies done by a group called the Truth About Cars showed that traffic deaths fell nine percent in states with legal use of medical marijuana.
9. Multiple studies showed that marijuana smokers were less likely to be risk takers than those that use alcohol. The studies showed that the marijuana calmed them down and made them actually pay more attention to their abilities.All of these tests and research studies showed that while some people think that marijuana is a major cause of traffic problems, in reality it may make the users even safer when they get behind the wheel!
10. Marijuana smoking drivers were shown to drive at prescribed following distances, which made them less likely to cause or have crashes.
Every test seemed to come up with these same results in all of the countries they were done in. Even so, insurance companies will still penalize any driver in an accident that has been shown to have been smoking pot, so this doesn’t give drivers free reign to smoke pot and drive.
So, the bottom line is that while alcohol has been shown in every single incident to have major problems and to have caused countless traffic crashes and fatalities, pot smoking overall has had none of these issues and in fact may make drivers pay more attention, drive slower and straighter and perhaps even stay home so they can’t be in an accident at all!
UI studies impact of marijuana on driving
