Are Marijuana Smokers Safer Drivers than Drinkers? Cannabis and Driving Compared

Updated on: August 11, 2025

This is the first blog in the new area of drugs that I will be blogging about – cannabis and driving. It may seem like I have to change the name of the website from Wigmore on Alcohol to Wigmore on Weed (WOW!). But actually, tetrahydrocannabinol (THC), the main psychoactive compound of marijuana, is an alcohol. That’s right – an alcohol, just like ethanol or methanol. The structure, metabolism, and effects are more complicated than for a simple molecule like alcohol, but it makes THC more interesting in some ways.

The structure of THC
Cannabis and Driving: The Stereotype vs. Reality
Key Takeaway on Cannabis and Driving
Conclusion
References

Are Marijuana Smokers Safer Drivers than Drinkers? Cannabis and Driving Compared

The structure of THC

THC is a hydrocarbon with just hydrogen, carbon and oxygen, and it is the –OH group which makes it an alcohol.

Cannabis and Driving: The Stereotype vs. Reality

The stereotypical view of cannabis and driving is that the driver becomes more cautious and drives slower than normal, leading to fewer accidents compared to alcohol-impaired drivers. Some studies support aspects of this idea. In one study, the postmortem blood samples of 372 drivers killed in Norway between 2005 and 2010 were analyzed for alcohol and 15 other psychoactive drugs, including THC. A driver was considered under the influence of alcohol if the BAC was 0.050 g/100mL or greater. The following table shows the Odds Ratio (OR) of fatally injured drivers being unbelted or speeding under the influence of alcohol or other drugs:

Cannabis and Driving chart, comparing alcohol and thc for speeding and unbelted

Interestingly, drivers with THC-only impairment were more likely than sober drivers to have been seat-belted—suggesting cautious behavior—but were still over 3X more likely to speed than sober drivers. The most unsafe drivers were those who had consumed alcohol.

Key Takeaway on Cannabis and Driving

I am not advocating smoking marijuana before driving, as it still increases crash risks compared to sobriety. The safest driver is a sober one. However, cannabis and driving may pose a smaller public safety risk than alcohol when it comes to traffic fatalities.

Conclusion

The study authors concluded:

“Excessive speeding is one of the main reasons for road traffic crashes and, together with being unbelted, the main reason for a fatal outcome. This behavior might in many cases be due to increased risk-taking or negligence of safety measures as a result of alcohol or drug use.”

References

Bogstrand, S.T., Larsson, M., Holtan, A., Staff, T., Vindenes, V., and Gjerde, H., “Associations Between Driving Under the Influence of Alcohol or Drugs and Speeding and Seatbelt Use Among Fatally Injured Drivers in Norway”, Accident, Analysis and Prevention, 78: 14-19, 2015
“Wigmore on Alcohol: Courtroom Alcohol Toxicology for the Medicolegal Professional”, Chapter 5, The Effect of Alcohol on Driving Ability, Irwin Law Publishing, 559 pp, 2011

FAQs

Is cannabis safer than alcohol when it comes to driving?

Studies suggest cannabis users may drive more cautiously than drunk drivers, but they still have higher crash risks compared to sober drivers.

How does THC affect driving compared to alcohol?

THC-impaired drivers are more likely to wear seatbelts but also 3X more likely to speed than sober drivers, while alcohol causes even riskier behavior.

Do marijuana smokers drive slower than drinkers?

Some research supports that stereotype, but speeding rates are still higher among THC users than sober drivers.

What were the key findings of the Norwegian driving study?

The study found alcohol-impaired drivers had the highest risk, while THC-only drivers showed mixed caution (more seatbelt use but more speeding).

Does THC show up in blood tests after crashes?

Yes, the study analyzed postmortem blood samples for THC and alcohol to compare impairment.

Is it safe to drive after using cannabis?

No—while risks may be lower than alcohol, cannabis still impairs reaction time and increases accident likelihood.

Why is THC considered an alcohol?

Its chemical structure includes an –OH group, classifying it as an alcohol (like ethanol), though its effects are more complex.

What’s the safest option for drivers?

Sobriety—neither alcohol nor cannabis impairment is safe behind the wheel.