Cannabis and Driving

What Level of Marijuana is Safe for Driving?

Unlike with alcohol, there is no science showing that drivers reliably become impaired at specific levels in the blood. Depending on the individual, drivers with relatively high levels of marijuana in their system might not be impaired, while others with low levels may be unsafe behind the wheel.

Research suggests that general marijuana impairment is highest within the first hour and tends to subside 4-6 hours after smoking or 6-8 hours after oral ingestion.  However, marijuana can affect people differently, making it difficult to make general recommendations about use.

Mixing Marijuana and Alcohol

Marijuana and alcohol are often used in combination with one another. Mixing alcohol and marijuana may produce effects greater than either drug on its own. The best available research suggests that both alcohol and marijuana use can impair critical driving functions.


Additional Resources

Learn the basics about cannabis and alcohol at

Read the research on the how cannabis compares to alcohol by the AAA Foundation for Traffic Safety: