Driving high

Is Driving High More Dangerous Than Driving Drunk?

As much as 20% of Canadians say that nothing could stop them driving high and 50% of cannabis users claim that the herb does not impair their driving skills. Are you one of them?

Some regular marijuana consumers feel very comfortable driving high, while others prefer not to take the wheel at all. This is a popular discussion topic between the cannabis and mainstream communities: is driving high as dangerous as driving drunk?

With more and more states and countries legalizing marijuana for medical and recreational use, many people are starting to freak out about all marijuana users that like to drive while high.

In all honesty, these are justified concerns, since the number of drivers under the influence of marijuana has increased in the states where the herb has been legalized. Even worse, the stats show that the car crashes in Colorado tripled after legalization.

By now, it is well-known that alcohol seriously impairs driving. Drunk drivers tend to drive in a more risky way usually by speeding and losing control of the vehicle. However, there is not enough evidence suggesting that marijuana-impaired driving is as dangerous as alcohol.

Here is a short summary of what the world has to say on driving high and what to expect when you get pulled over under the suspicion of driving high.

Studies on Driving High

The evidence from various studies suggests that marijuana does have a significant influence on mental and motor skills, but not nearly as much as alcohol.

The review of motor vehicle crashes from 2002 was not able to prove that stoned drivers were more likely to be involved in car accidents than drug-free drivers.

Almost 8 thousand driving records were reviewed and all they could make was one conclusion:

People driving under the influence of marijuana are more aware of their impairment so they tend to slow down, but their reaction times are slightly slower.

However, one other research from 2014 suggests that people who don’t use marijuana that often are more likely to be impaired than more regular or daily users. The researchers suggested that THC sensitivity is a key point here — occasional consumers are less tolerant to the compound while regular users are more tolerant and develope something like a resistance.

As they suggested, this is probably the reason why regular consumers feel more comfortable when driving high.

On the other hand, Professor Mark Asbridge and his team from Dalhousie University concluded in their study that operating a motor vehicle right after consuming marijuana almost doubles the risk of being involved in car accident. But, if smoked, THC declines rapidly in blood and so is the impairment, says Professor Asbridge.

Here is a video example of a simple but reliable experiment. Three heavy, regular and occasional users took the wheel after smoking different doses of marijuana.

Video Source: CNN

I’d have to agree with a YouTube comment which says that you have to smoke a lot of weed to be impaired. The subjects in this video were driving with 5 times the legal limit of THC (5 ng/mL) and still drove acceptably well.

Laws on Driving High

In Canada, driving high is forbidden by the law and is considered an offense.

In fact, in most legislatures, high driving is considered a DUI offense. Driving under the influence of drugs and alcohol is a criminal offence leading to monetary penalties, even prison (depending on the country).

In United States, however, Washington and Colorado have gone a step further and set up a somewhat reasonable limits.

Both states allow people to drive under the influence of marijuana. The allowed amount of THC in blood is 5 nanograms per milliliter of blood. Driving with a higher amount of THC of blood is a criminal offense and can lead to serious legal consequences.

For reference, a study published in Drug and Alcohol Dependence, says that a person driving with 13 nanograms of THC has the same level of impairment as those driving with 0.08% of alcohol.

This confirms the message of the above video. You need to smoke a ton of weed to be unable to drive.

Here’s what you can expect if you’re caught driving high in Canada.

Penalties for driving while high in Canada

Smoke in the car

Currently, it is illegal to drive under the influence of marijuana but there is no specified limit of THC in blood. Large part of that is the difficulty of testing the drivers and proving the driver was high at the time of offense. Right now, this is mostly checked through field sobriety tests and the penalties for first time offenders are strict:

  • $1,000 fine
  • License suspension for 1 year
  • Mandatory education or other treatment program

For second and third-time offenders, penalties are even more severe, ranging from 1-4 months in jail, lifetime license suspension and tens of thousands of dollars in fines.

When the plant becomes fully legalized in the summer of 2018, there will be a new bill handling this issue. According to Health Canada backgrounder:

  • 2 nanograms (ng) but less than 5 ng of THC: Having at least 2 ng but less than 5 ng of THC per millilitre (ml) of blood within two hours of driving would be a separate summary conviction criminal offence, punishable only by a fine. This lower level offence is a precautionary approach that takes into account the best available scientific evidence related to cannabis. This offence would be punishable by a maximum fine of up to $1,000.
  • 5 ng or more of THC: Having 5 ng or more of THC per ml of blood within two hours of driving would be a hybrid offence. Hybrid offences are offences that can be prosecuted either by indictment, in more serious cases, or by summary conviction, in less serious cases.
  • Combined THC and Alcohol: Having a blood alcohol concentration of 50 milligrams (mg) of alcohol per 100ml of blood, combined with a THC level greater than 2.5 ng per ml of blood within two hours of driving would also be a hybrid offence.

This will be, of course, combined with the number of previous offences:

  • First Offence: $1,000 mandatory minimum fine
  • Second Offence: mandatory 30 days imprisonment
  • Third Offence: mandatory 120 days imprisonment
  • Testing for Marijuana Impaired Driving

There are a few ways police tests drivers for marijuana impairment.

Usually, when you are pulled over under the suspicion of driving high you will be asked to take a roadside sobriety test, which involves a series of tasks such as horizontal gaze, walk-and-turn or one-legged stand.

Conventional breathalyzer test can’t detect the presence of marijuana. So, if you (or the driver) pass the FST and officers still suspect that you’re high, you could be asked to provide a blood or urine sample.

Testing Method Occasional smoker Casual smoker Everyday smoker
Blood 1-2 days 3 days 7 days
Urine 7 days 10-18 days 30-48 days
Saliva 1 day 3 days 7 days
Hair Up to 90 days
Sweat 7-28 days

THC stays in urine much longer than in the blood. But, there is a major problem when it comes to both types of testing. The thing is, those tests can’t determine when exactly cannabis was consumed. Blood and urine tests detect THC weeks after using marijuana.

The presence of THC in the blood does not necessary mean that the person is or was impaired. When marijuana is consumed, its effects last only for a few hours but THC remains in the system much longer than that. And that’s the whole point of not being able to determine precisely if someone is driving under the influence of marijuana.

Right now one more test is being used — saliva testing. THC can be identified in saliva one hour after consumption and stays there for 1-7 days. When pulled over, you can be asked to provide a saliva sample through placing a cotton swab in your mouth. Results are, however, still the same. The driver can test positive on marijuana but its effects may no longer have an impact.

Since these tests can’t tell us whether the driver was impaired for sure, Drug Recognition Expert (DRE) officers are now taking over the scene. They are trained to recognise the physical signs of marijuana impairment by examining driver’s eyes, muscle tone etc.

As marijuana consumption becomes more accepted worldwide, the number of high drivers will definitely increase, as we’ve seen in the case of Colorado and Washington.

However, for everyone’s sake, it’s important to keep the roads safe. With cannabis becoming fully legal in Canada, we can expect more sensible laws on driving high. Right now, driving under the influence of any psychoactive substance is illegal in Canada and regulated in the US.


In charge of Greencamp’s health section, with a decade long experience of using cannabis for stress relief. Her spare time is mostly divided between Irish dance and reading.

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