What is the legal limit for impairment?

Under Colorado law: 

  • If a person’s ability to operate a vehicle is affected to the slightest degree by alcohol and/or drugs they can be arrested for a DUI or DWAI.
  • Delta 9-tetrahydrocannabinol (Delta 9 THC) is the psychoactive substance that creates impairment from using cannabis. Delta 9 THC becomes inactive once metabolized by the body - but that can take hours to happen and leaves you at risk for a DUI.
  • The limit in Colorado of active Delta 9 THC in a driver's blood, which gives rise to a "permissible inference” that the person is under the influence of cannabis, is five nanograms or more per milliliter in the whole blood.
  • Drivers can be arrested and cited for impaired driving if law enforcement observes and documents driver impairment to any degree, even with a blood level below 5 ng of Delta 9 THC.
I’m a medicinal marijuana user, can I still be arrested for driving impaired?

Yes. If you are impaired while driving, even as a medical cardholder, you are at risk of getting a DUI.

What if I have THC in my system because I consume cannabis frequently, but I'm not impaired and are pulled over and tested?

Psychoactive impairment is caused by active Delta 9 THC, which becomes inactive over time and is stored in the body for longer periods. The primary determinant is the driving behavior and observed level of impairment witnessed and documented by the law enforcement officer. Arrests are made on observed impairment. Any level of active THC in your blood can put you at risk of a DUI.

What are the fines for impaired driving?

Fines range from $200 to $1,500. Additional fees can make the fiscal cost of a DUI more than $13,500.

Are people really arrested for marijuana-impaired driving?

Yes, all Colorado law enforcement officers receive training in impaired driving detection. Many receive additional advanced training in detecting impaired driving from drugs. On average, more than 60 people are arrested each day in Colorado for DUI, including drugs, alcohol or a combination of both.

What are some effects of marijuana impairment?

Cannabis has measurable physiological effects that impair the ability to drive and react quickly in critical situations. There are numerous independent studies that have shown cannabis impairs critical abilities needed to drive safely, including:

  • Slowed reaction time
  • Difficulties in road tracking and lane-position variability
  • Decreased, divided attention
  • Impaired cognitive performance
  • Relaxed Inhibitions
  • Impaired executive functions, including route planning, decision making, and risk taking, or a combination of all

Regardless of the impairing substance, the skills needed to drive safely are negatively impacted by many drugs, including cannabis.

How are law enforcement officers trained to recognize impairment? What is a DRE?

Colorado law enforcement officers are trained in the detection of impairment of alcohol and drugs, and many are specially trained Drug Recognition Experts (DRE). These officers have the ability to detect physical and psychophysical signs of drug impairment. DREs are viewed as one of the most effective law enforcement tools in efforts to reduce drugged driving. There are currently 226 active DREs representing 79 law enforcement agencies across the state, including 62 with the Colorado State Patrol

How is impairment tested? (Can they really tell if I'm high?)

Anyone arrested for suspected DUI is required to submit to chemical testing. The toxicological sample is then tested at a laboratory.

How much marijuana can I legally carry in my car?

No open containers:

  • Neither drivers nor passengers are allowed to open any cannabis packaging or use the product while in a vehicle.
  • You can be charged with a traffic offense if the cannabis product seal has been broken, some of the product has been consumed and there’s evidence that it was used in the vehicle.

All drivers and passengers are also required to abide by the possession (quantity) limits set by the state.  Adults 21 and older can have up to 2 ounces of cannabis.

A note on combining cannabis and alcohol

If you are contacted by law enforcement and evaluated for impairment — even if your blood alcohol level and Delta 9 active THC level are below the legal limit, you can be arrested for DUI, as cannabis amplifies the effects of alcohol and impairment.