Marijuana, Alcohol and Driving

Photo credit - Smoking and Driving?

"If people who would ordinarily drink and drive instead choose to smoke and drive, that may be safer for the population as a whole." - Benjamin Hansen Researcher, U of O.

Of course, everyone should know that it's not a good idea to drive while stoned.  But the studies show that marijuana users have the same rate of accidents as non-users, and that people impared with alcohol have a ten fold likelyhood of getting into an accident.  While marijuana can cause spatial imparement, users also tend to be cautious, and perhaps this is why there are few incidents among the toking population.

According to a recent Gallup poll, the majority of American's thinks that smoking weed while driving is not a big problem. It isn't that dangerous. In contrast, the majority thought that drinking and driving was definitely a big issue.


To address the question, is driving after smoking Marijuana with any intelligence, we should look at the variables involved. How much Marijuana did the driver smoke? What kind of weed was it?  Was it high as shit in THC, or was it a nice smoke of day weed.  Metaphorically speaking, are we talking about the marijuana equivalent or a beer or a pint of whiskey here.

“Crash culpability studies have failed to demonstrate that drivers with cannabinoids in the blood are significantly more likely than drug-free drivers to be culpable in road crashes.” - 2002 Study

Understand Marijuana Drug Testing



For some individuals, both Marijuana and Alcohol in small quantities can be performance enhancing.  For the sake of argument, moving forward, let's assume that we're talking about driving while being moderately stoned on Weed high in THC. Few studies have looked at the differences between Day and Night weed - in the operation of complex machinery. These are the important issues that lie at the heart of doing intelligent research and analysis in this issue.


Marijuana in excess has been shown to impair spatial judgement, motor coordination, visual function and divided attention.  However, a common Cannabis side effect includes paranoia, causes some drivers to drive very slowly, carefully - to avoid imaginary accident possibilities.  It is interesting to see how the negative effects can cancel one another out.


"You know the cops are looking to bust everyone these days." - Paranoid pot smoker who drives real slow.

In driving simulation studies they looked at how Pot impairs cognitive function, there is some impairment, but in many cases, not significant. And also under consideration is the fact that many of these subjects would choose not to drive while tolking.  If might be said that Pot tells the truth while alcohol is self-deceptive.


"To be perfectly clear: It's always safer to drive when you're not stoned." - Hansen

Strangely, a study found that drivers that used a Vape, tended to weave within their own lane more than sober drivers.  However the Vape group were not more likely to go out of their lane, nor were they prone to speeding.  In comparison, drunk drivers commit all three violations.  The conclusion from these types of studies is that Marijuana users do not tend to drive dangerously.  This notion is supported by most traffic police, who say that there is no comparison between Alcohol and Weed. Alcohol is an order of magnitude worse. 

“Cannabis leads to a more cautious style of driving, [but] it has a negative impact on decision time and trajectory. [However,] this in itself does not mean that drivers under the influence of cannabis represent a traffic safety risk. … Cannabis alone, particularly in low doses, has little effect on the skills involved in automobile driving.” -  Canadian Senate Special Committee


Some studies found that Marijuana smokers might be slightly more likely to die in an auto crash, but the data was unconvincing, was not statistically significant.  The drivers in the study were not necessarily using Marijuana at the time of the accident. Testing only indicated if THC was in their system within the last few months.

There is no way to measure Marijuana, or THC with a breathalyzer.  THC is not volatile and will not come back out in the lungs during respiration.  Blood tests can definitely reveal THC content, which is really the only useful number to associate THC with accidents and impaired driving.

Thankfully, researchers looked at the practical side of Marijuana use.  Some studies found that MMJ users effectively compensate for their impairment.  They are aware of their skill level and drive more like a little old lady, who never gets in accidents, but really would not impress anyone on any test with her abilities.  In addition, one third of Pot smokers that tested not impaired, considered their driving ability to be impaired from the pot that was freshly consumed!! 


Drunks on the other hand, often don't recognize they are impaired.  They think they are at the height of their game and drive faster, taking ridiculous chances and make really bad decisions.


A study found that in 2013, the year after medical marijuana laws were passed, traffic fatalities fell with the sharpest reductions being evening accidents and drunk-driving or alcohol-related accidents.

"I speculate that the reduction in accident fatalities were due to more people were smoking marijuana instead of drinking."  - Hansen National Bureau of Research



Legal limits

Lawmen are looking at the data, their own findings and conclude that maybe setting legal marijuana blood limits does not benefit the public and amount to a waste of taxpayers money and police time and effort.

Smoking a joint typically raises a person's THC levels to about 20 micrograms per liter..In a Drug Dependence study, within-lane weaving began to occur once the person's blood levels reached about 13 micrograms of THC per liter of blood but the legal limit for THC in Washington and Colorado is set a 5 micrograms per liter.

Interestingly, some studies indicate that THC and ethanol (alcohol) have an additive effect and blood combined blood levels need to be taken into account to assess impairment.


Operators of passenger cars, trucks, and motorcycles - who died within 4 hours of their crash were tested for THC. The results:

“Blood specimens were collected from a sample of 1,882 drivers from 7 states, during 14 months in the years 1990 and 1991 - While cannabinoids were detected in 7 percent of the drivers, the psychoactive agent THC was found in only 4 percent. The THC-only drivers had a responsibility rate below that of the drug free drivers - While the difference was not statistically significant, there was no indication that cannabis by itself was a cause of fatal crashes.”

MMJDOCTORONLINE Notes:  If you smoke Marijuana for medical purposes, do you agree? It is a good idea to be legal.   Click here to find out how you can get a legal recommendation for medical marijuana completely online at a fraction of the cost for a clinic visit. 

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photo credit

Johnny Depp - Fear and Loathing - Stoned and Driving


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Why drink and drive when you can fly?


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