Driving under the influence doesn’t just mean drinking and driving. It also refers to driving under the influence of drugs (DUID), a growing concern and factor in impaired-driving crashes.

The recent passing of Proposition 207, which legalized recreational marijuana in the state of Arizona, raises new concerns about not just alcohol-related crashes, but driving under the influence of marijuana. Not only is cannabis being more widely used, potency is on the up, as well. 

In fact, marijuana is the most commonly used drug by the age group that has the most road traffic accidents. 

Just because marijuana use is legal does not mean it’s ok to drive while under the substance’s influence. Same goes for driving under the influence of opioids like oxycodone, vicodin, or codeine. You may have a prescription from your doctor, but you could still receive a ticket for driving while high or stoned. 

So, what exactly are the risks of driving while under the influence of marijuana? 

The truth is, the effects of cannabis on driving are still being studied. However, a number of studies and statistics do show there is significant cause for extreme caution. 

The risk: Impaired driving

In multiple studies, cannabis has been found to acutely impair skills people use when driving, such as attentiveness, vigilance, perception of time and speed, and use of acquired knowledge. Same goes for reaction time, tracking, motor coordination, visual functions, and particularly complex tasks that require divided attention. 

The risk: Increased possibility of causing a crash

Marijuana is the illicit drug found most recently in the blood of drivers who have been involved in motor vehicle crashes, including fatal crashes. And drivers in vehicle crashes who have THC in their blood are three to seven times more likely to be responsible for the crash. 

The risk: It’s difficult to define “impairment”

When it comes to cannabis, Impairment is difficult to ascertain. This is different from alcohol impairment. Alcohol’s effects can be tracked. We know precisely how it’s absorbed, distributed, and eliminated from the body, and we know how it impacts the brain and body. There are documented charts that tell you based on your weight and gender how many drinks you can have and still remain under the illegal blood alcohol concentration (BAC) for driving. 

But with marijuana, we’re in undocumented territory. When it comes to weed and other substances, there are more variables and complexities that make the level of impairment an unknown — at least for now. 

What happens if you get pulled over while high? 

Here in Arizona, we have a zero-tolerance law — meaning that driving with any amount of THC and/or its metabolites in the body is strictly prohibited. 

The Arizona Department of Public Safety website states, “If you are pulled over and suspected of driving under the influence of alcohol or drugs through field sobriety testing, a chemical test will be administered.” 

While there is no breathalyzer test for cannabis, law enforcement can use a drug influence evaluation (DIE) administered by a drug recognition expert (DRE), to discover evidence that you’re driving while impaired. Arizona’s Drug Evaluation and Classification program has been recognized nationally for its success in identifying drug-impaired drivers.  

Bottom line: Drugs and driving don’t mix. 

Those who partake of cannabis should have a designated driver, or wait at least three to four hours after ingesting it in any form. They should also be aware that use of alcohol and marijuana (or mixing other substances, including opioids) can cause much more impairment than if either drug is used on its own. 

Stay safe out there. Stop and Go Driving School is committed to educating drivers to keep themselves and others safe on the road. Check out our defensive driving and Alive@25 classes to learn and practice the skills you need to reduce your risk of being hurt or killed in a vehicle crash.