Research Project on Cannabis-Impaired Driving FAQs

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The Research & Development Branch of the California Department of Motor Vehicles (DMV R&D) is set to begin recruiting approximately 300 volunteer participants for an innovative research project of potentially historic importance on the subject of cannabis-impaired driving. This study has received federal and state approvals and relies on funds allocated to the California Highway Patrol (CHP) for research in matters related to cannabis-impaired driving under Senate Bill 94 (Statutes of 2017). DMV R&D is conducting this project in collaboration with the Center for Medicinal Cannabis Research at the University of California, San Diego.

The study will begin in August 2023. It will take between nine and 18 months to test 300 participants in a controlled environment.

The recent legalization of cannabis for recreational consumption presents challenges for the policing of impaired driving. Cannabis affects driving in ways that are distinct from other substances and, unlike alcohol, the severity of the effects cannot be known based only on the levels of its active compounds in the body.

This study has two goals: to investigate the effects of cannabis consumption on driving abilities and to test the validity of various methods used by law enforcement to detect cannabis-impaired driving. Because a number comparable to .08% BAC does not exist for cannabis, the current enforcement of cannabis (and other drug) impairment must rely to a greater extent on behavioral methods of detection. These include the various cues that law enforcement officers are trained to look for, including erratic driving behaviors, field sobriety tests, and an additional evaluation from a Drug Recognition Expert (DRE) to determine the substance(s) causing impairment.

Participating drivers will smoke a real cannabis cigarette, a placebo one, or no substance. They will then complete a series of driving tasks by operating an actual car within a safe, closed-course environment at the CHP Academy in West Sacramento. An examiner and a researcher will be in the vehicle with the participants to assess their driving and cognitive skills. In addition, the car will be equipped with state-of-the-art instrumentation that continuously record driver actions as well as vehicle movements and position to the accuracy of 2 centimeters. Finally, participants will undergo a series of behavioral assessments conducted by trained CHP officers to detect potential cannabis impairment.

Yes. Volunteers who are selected to participate in the study will have small amounts of blood drawn three times during the course of the experimental session, and the samples will undergo toxicology analyses.

This study will feature several important elements that have never been combined in a single study. It will be a true experiment with random double-blind assignment and a true control condition, meaning that neither the participants nor any of the personnel involved in the assessments (researchers, examiners and officers) will know whether a driver consumed real cannabis at the time of participation. This is the gold-standard of experimental design in behavioral research, as it minimizes the likelihood of expectations affecting the results. Together with the enrollment of a large sample of volunteers, this allows for strong conclusions to be made about causal mechanisms and statistical associations.

The study will also be one of only a couple to test behavioral methods of detecting cannabis impairment among drivers of an actual vehicle (as opposed to a simulator), and the first to do so with the aid of instruments that vastly increase the precision and resolution of objective data measurements.

The DMV received approval for this study from the U.S. Food and Drug Administration, the U.S. Drug Enforcement Administration, the Research Advisory Panel at the California Department of Justice, and the Human Research Protections Program at the University of California, San Diego.

Senate Bill 94 (2017) authorizes this type of research. In addition, California Vehicle Code §23152.5 allows a person who is under the supervision of, and on the property of, the California Highway Patrol, to drive a vehicle while under the influence of a drug, or while under the combined influence of a drug and alcohol, for the purpose of conducting research on impaired driving.

Traffic safety stakeholders at the local and national level have already expressed great interest in the results of this study, however, a large sample of volunteers is needed to draw valid conclusions. By volunteering to participate in this study, you would be contributing to traffic safety and the prevention of impaired driving. In addition, volunteers who are selected for the study will be compensated up to $150 for their participation.

The DMV is looking for approximately 300 volunteers who must:

  • Be between the ages of 21 and 55
  • Possess a valid California driver license
  • Be a cannabis user, and 
  • Live within approximately 15 miles of the CHP Academy in West Sacramento. 

Recruitment will begin in mid-July 2023. Express your interest in volunteering.