What are the laws about marijuana and driving?

Driving while impaired is illegal and unsafe. Getting high before you drive will get you arrested for a driving under the influence (DUI) charge. This is still true even though marijuana is legal for adults.

If you are high, you should not drive, bike or operate machinery. Marijuana use affects:25
  • Reaction time
  • Short-term memory
  • Hand-eye coordination
  • Concentration
  • Perception of time and distance 
People may think that they are “safer” drivers while stoned since they drive more slowly. However, research shows that driving while high may double your risk of a crash.18

Similar to alcohol, there is an established impairment level for marijuana in Colorado. By law, drivers with five nanograms of delta-9 tetrahydrocannabinol (THC) per milliliter of whole blood can be prosecuted for DUI. Even if marijuana is used medically, officers can arrest you based on impaired driving behaviors.

It also is illegal have marijuana in the passenger area of a vehicle if the seal has been broken, some of the product has been consumed and there is evidence it was used in the car.

How long should I wait after using marijuana to drive?

For occasional users, using 
10 mg or more of THC is likely to cause impairment. This impacts your ability to drive, bike, or perform other safety-sensitive activities.1 
  • Smoking: Wait at least 6 hours after smoking up to 35 mg THC before driving or biking. If you have smoked more than 35 mg, wait longer.1 
  • Eating or Drinking: Wait at least 8 hours after eating or drinking up to 18 mg THC before driving or biking. If you have consumed more than 18 mg, wait longer.1  
  • Marijuana affects individuals differently: These times are estimates based on research findings. If you are unsure how marijuana will affect you, make other plans for transportation or don't drive.1 
  • Multiple Substances: Using alcohol and marijuana at the same time is likely to result in greater impairment than either one alone.1 
Check out the Colorado Department of Transportation’s “Drive High, Get a DUI” campaign and read the frequently asked questions for more information on marijuana and driving in Colorado.