Weed DUI: Is it a Real Thing?

Everything you need to know


More and more states are now legalizing weed either for medicinal or recreational use. It may, therefore, come as no surprise to learn that marijuana is the drug responsible for the most traffic accidents, except for alcohol.

Despite this, there is a real lack of understanding surrounding weed DUIs. It is not easy to assess how badly a driver is impaired by marijuana using standard roadside tests, and this makes weed DUIs far more complex than those associated with alcohol. Laws on cannabis DUIs also vary from state to state, adding further to the confusion.

In today’s article, we discuss weed DUIs in detail and ask whether you should even think about getting behind the wheel while high.

How Big a Problem is Weed DUI?

After alcohol, pot is the drug most commonly involved in car crashes. There are a couple of different reasons for this, with the first being availability. It is becoming easier to get your hands on high-quality bud all the time as marijuana legalization sweeps across the states and more licensed dispensaries pop up by the day.

Another reason why weed DUIs are so common is demographics. The group of people most likely to use cannabis recreationally is young males. These are also the people who have the most car accidents, with as many as a quarter of crashes involving drivers under the age of 25.

It is difficult to find reliable facts about how many people drive under the influence of weed, but in one survey, almost 10% of users admitted to driving while high and they did so an average of eight times a year. However, another study found that as many as 43% of its respondents had driven under the influence within the past year. That’s quite a difference!

Although the exact figures on weed DUI are not available, one thing is clear: Driving while high is a significant problem, and it is likely to remain that way for the foreseeable future. So, what exactly constitutes a weed DUI? Let’s take a look at the law.

Weed DUI Laws

The laws on weed DUIs vary from state to state. For example, in Colorado, you can be prosecuted if you have blood THC levels of 5ng/mL or more. Open container laws apply, and if you refuse a blood test, you could be classed as a ‘high-risk driver’ and subject to administrative penalties such as alcohol education or mandatory therapy.

The 5ng/mL level is shared across several other states, including Washington and Montana. However, many other states will prosecute if they detect any amount of THC or its metabolites in your system. In the UK, the threshold for prosecution is 2ng/mL, and punishments include:

  • A minimum one-year driving ban
  • An unlimited fine
  • Up to six months in prison (up to 14 years in the case of a fatality)
  • A record of your DUI on your driver’s license for 11 years

In the US, punishments for weed DUIs will vary depending on where you live. For a state by state summary of marijuana DUI laws, check out this report from the National Highway Safety Traffic Administration. Skip to page 25 to read about Drugged Driving Per Se Laws.

Detecting Weed DUI

If you are suspected of driving under the influence, you may be asked to perform a Standardized Field Sobriety Test to determine your level of impairment. You may also be required to take a drug test which could involve testing samples of blood, urine, saliva, or even sweat for THC and its metabolites.

Unfortunately, there is currently no accurate way to correlate your THC levels with your ability to drive, though. This is because THC levels peak within a few minutes of smoking and could be reduced by as much as 80–90% after 30 minutes.

Maximum impairment is thought to occur somewhere between 20–30 minutes after smoking, but this figure varies between individuals. It is difficult to say precisely how much a particular person is affected by a set dose of marijuana as it depends on many factors including body weight, tolerance, food and drink consumption, and so on. Therefore, your THC levels could be below the legal threshold a few hours after smoking, but there is still a chance your driving could be impaired.

Another issue with detecting weed DUIs is that THC and its metabolites are fat soluble. This means that if you use pot regularly, THC metabolites are stored in your fat reserves and released gradually over time. It can take 30 days for your system to clear itself completely, meaning that THC could still be detected in your blood even if you haven’t smoked for several weeks!

This means that, unlike alcohol, it is challenging to correlate specific THC levels in the blood with dangerous driving. Let’s see what the research has to say.

Research on Weed DUI

Due to its status as a Schedule I controlled substance, there is far less research on weed DUI than there is on drunk driving. The evidence is also somewhat inconclusive regarding how dangerous driving while high really is.

The National Institute on Drug Abuse summarizes that while some studies show as much as a two-fold increased risk of crashing while driving high, others suggest that there is no significantly increased risk once age, sex, and the presence of alcohol have been taken into account.

Another review published in the American Journal on Addictions highlights the dangers of driving under the influence of cannabis. The drug is known to cause several significant cognitive impairments, including:

  • Slower reaction times
  • Reduced attentiveness
  • Issues with road tracking
  • Poor target recognition
  • Reduced executive function (decision making, route planning, etc.)

However, the authors of the study go on to state that there is not enough conclusive evidence to determine just how dangerous weed DUI can be.

Should You Consider Driving While High?

In spite of the above cognitive impairments, many people claim that they actually drive better while high! Could this be even remotely true?

It seems that this idea is not quite as crazy as it sounds. Pot smokers tend to overestimate their level of impairment (in contrast to drinkers who tend to underestimate) and compensate by changing their behavior accordingly.

After smoking cannabis, people tend to drive more slowly and spend more time below the speed limit than usual. They also tend to keep a greater distance between themselves and the car in front and are less likely to overtake.

These effects are opposite to those of alcohol, which include faster driving, greater speed variability, and more time spent driving over the speed limit. But this does not mean that driving while high is safe.

Sure, driving high may safer than driving drunk, but driving too slowly can be dangerous too. It is also crucial to remember that how high you feel is not necessarily the same as how high you are. You might think that you are fine to get behind the wheel, but in reality, your reactions could still be significantly impaired.

Therefore, if you are heading out for a smoking session, you should apply the same rules as if you were hitting a bar. Assign a designated driver to remain sober, or simply leave the car at home and take a cab or public transport instead. This might seem like a drag, but it has to be better than putting your life (and others’ lives) at risk!

Final Thoughts on Weed DUI

Weed DUIs are a significant problem, accounting for the second highest number of traffic accidents after alcohol. However, laws on driving while high are not as clear-cut as those relating to alcohol for a number of different reasons.

For one thing, it is challenging to detect THC levels in a driver’s blood accurately, and even if this were possible, it still would not necessarily offer a true representation of that person’s level of impairment. This makes weed DUIs a complex issue, and one with no obvious solution in sight.

What is clear, though, is that more research into the subject is needed, both to develop more effective testing measures and to confirm just how dangerous it is to drive while high. In the meantime, we recommend that you exercise caution and resist the temptation to get behind the wheel if you are in any doubt at all.

Stay safe, people, and always enjoy your marijuana responsibly!

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