Free Consultation | Se habla español


when you need it most

Photo of Herbert J. Weston and Tanya L. Weston

Marijuana use and its impact on driving simulator performance

On Behalf of | Jan 19, 2023 | Drug Crimes

Some people in California feel marijuana is a safe drug that allows users to function competently while under the influence, including safely driving a car. While this could be true for some people, getting high effects each person differently.

Researchers have studied a group of marijuana users using a driving simulator to gather more definitive and precise information on how marijuana use affects driving capacity as the effects of the drug wear off.

The effects of marijuana on driving

Some people feel they can still function normally while under the influence of marijuana. However, they may find that their reaction times have slowed. Their awareness and ability to brake, swerve or accelerate in a split-second to avoid an accident suffers measurably.

Mechanics of the study

Researchers at the University of California, San Diego, gave joints to almost 200 study participants, with instructions to smoke them at home under their typical usage habits. The participants then went through a computerized driving simulation test at specified intervals to test their levels of impaired driving as the high wore off.

Study Results

The study results, published in the journal JAMA Psychiatry, showed that about half of the participants thought, after 90 minutes, that they could drive normally, with no impairment. The other half felt they were too impaired to drive.

The simulator tests showed that, instead of 90 minutes, drivers needed about 3.5 hours for the high to wear off enough for them to drive normally and 4.5 hours for them to drive as well as a placebo group.

Issues for consideration

Some individuals perform poorly with minimal THC in their blood, while others with higher THC levels perform without significant impairment. Taking the risk of driving after getting high can result in a DUI/DWI arrest.

Police currently use standard road sobriety tests and their judgment to decide whether a driver is too high to drive safely. Unsuccessful attempts have been made to create a blood test that measures THC levels to aid police officers in detecting driver impairment. However, research has shown no correlation between a person’s blood level of THC and performance.

Police in some states use oral swab tests to detect the presence of drugs, but even if drug use is detected, the results cannot determine whether a person is impaired.

Additional tools and more research may help law enforcement to detect impaired drivers better, but the technology is still in its infancy.