Study Shows Danger Drug- And Alcohol-impaired Driving Poses In Colorado

Key & drink

New research shows that drivers who use alcohol and marijuana in conjunction may experience greater intoxication and more severe impairment.

Drug- and alcohol-impaired driving has become a growing source of concern in Denver in the wake of marijuana legalization. Already, drunk driving accidents cause over one-third of Colorado traffic deaths in an average year, according to the Colorado Department of Transportation. The same source reports that in 2013, drivers who were impaired by drugs contributed to 21.4 percent of all fatal accidents.

Unfortunately, the way that marijuana affects accident risk or interacts with alcohol to alter driving performance is not well understood. As a result, many Colorado residents and tourists may make the reckless decision to drive after using both substances. Troublingly, new research suggests that these drivers may be likelier to cause accidents, even when they have consumed amounts of each substance that wouldn’t normally cause marked impairment.

A risky combination

According to Time magazine, the National Institute on Drug Abuse recently published the results of a study into the effects of marijuana and alcohol on driving ability. The study focused on 18 men who reported occasionally using marijuana. Each man performed six 45-minute driving simulations after ingesting a combination of marijuana and alcohol. The researchers tested the effects of different blood-alcohol and blood-THC concentrations during each drive.

The researchers found that marijuana and alcohol had amplifying adverse effects on driving performance. For example, when used on its own, marijuana made drivers more likely to drift into other lanes. The participants had marked difficulty staying in their lanes when their blood-THC levels reached .13 nanograms per milliliter, which is over twice Colorado’s legal limit. However, when the participants consumed even small amounts of alcohol, they began drifting at lower blood THC levels.

The study also yielded other worrisome findings. The researchers noted that the combined use of alcohol and marijuana caused peak impairment from alcohol to occur at a later time. This could make it harder for people to recognize that they are impaired and incapable of driving. People who smoked marijuana while they were drinking also experienced more effective uptake of THC, which resulted in a stronger high. This could make these drivers more likely to cause serious car accidents.

Dangerous impairments

Many people may take a casual view of driving after using marijuana, especially when they contrast it to the well-established dangers of drunk driving. However, according to the Colorado Department of Transportation, marijuana use is known to cause several effects that can prevent a person from driving safely. These include:

  • Delayed reactions to stimuli
  • Incorrect perception of space or time
  • Reduced hand-eye coordination
  • Impaired active memory
  • Diminished ability to focus

When combined with the impairing effects of alcohol, these handicaps may have catastrophic effects.

Sadly, statistics show that impaired drivers may contribute to a substantial number of accidents in Colorado this year. When these drivers cause crashes that result in injury to others, legal remedies may be available. Anyone who has suffered harm because of an impaired driver’s reckless actions should consider discussing the situation with our Colorado car accident attorney.


Michael established The Sawaya Law Firm in 1977 and built it into one of the largest personal injury law firms in Colorado, with more than 20 lawyers and 80 staff members serving clients from five offices located in Denver, Greeley and Colorado Springs. Throughout its history, the firm has stayed true to its 12 Core Values, which emphasize excellence in advocacy and a commitment to providing outstanding client service. Michael studied sociology and economics as an undergraduate student at The Colorado College, and he earned his law degree from the Texas Tech University School of Law. In addition to being involved in several legal and community organizations, Michael enjoys playing music and cooking, and he has written a book on spiritual matters.