Does Cannabis Affect Your Ability to Drive?

Stephen Andrews
23 Feb 2024

Some cannabis users report that their vision and motor skills are much better after they’ve toked. But they just might be under the wrong impression. It’s widely accepted that marijuana can slow your reaction time, impair judgement of distance, and it affects body coordination. All of these things are essential when you operate a vehicle. Effects from THC need hours to go away, therefore the general advice is that users wait before they hop in the car, or find other means of transport to get safely to their destination.

Friends don’t let friends drive drunk, goes a famous saying about drunk driving. But what about using weed? 

Driving under the influence of cannabis has become an important public safety concern with the advance of legalization in the U.S. Marijuana is the second most commonly detected substance after alcohol in both crash-involved drivers and the general driving population, according to the National Highway Traffic Safety Administration (NHTSA). 

The dangers of drunk driving and driving under the influence of THC are relatively similar, especially if a person has been exposed to too much alcohol or some particularly potent marijuana product. However, the same cannot be said about CBD, which is pretty much harmless. 

The NHTSA is already participating in a drug-impairment driving prevention campaign, which says, If You Feel Different, You Drive Different. And it’s only fair to admit that after smoking marijuana you do feel different. The campaign aims to make driving under the influence of THC cannabis as socially unacceptable as drunk driving. 

Marijuana Effects Impair Ability to Drive

While the therapeutic qualities of marijuana are numerous, THC-rich products may cloud your thinking and sense of judgement. The more you use, the more you stay in the altered (and often enjoyable) state of mind. 

Some of the common effects from smoking weed include a distorted sense of time and space, and motor skills are also being affected. That includes skills that involve your muscles executing specific actions, which makes driving when high more dangerous. 

Acute impairment from THC follows in the first few hours of smoking. It would be different for anyone. It’s also important to note that the presence of THC in screening tests (such as blood and urine tests) will not necessarily indicate an acute impairment. Simply, everyone who indulges in cannabis should be aware of the risks of dangerous drinking immediately after that. 

A conclusion from a recent study that looked at acute driving impairment from cannabis implicates that users should consider the “risks of impairment for at least 5h after using a THC-containing cannabis products alone and longer if concomitant with alcohol or other substances.”

It notes that users should even opt for “complete abstention from driving after cannabis use for a significant period,” or at least 12 hours. 

The study, published in the journal Med Cannabis Cannabinoids in 2023, looked at both THC cannabis use and a combination of THC and CBD, using on-road driving tests with real-world conditions. 

The same research further says that “CBD-dominant cannabis did not produce significant cognitive or psychomotor impairment compared with placebo or trial.”  

In addition, the study authors recommend that clinicians who prescribe medicinal cannabis should inform their patients of the risks of driving under the influence of cannabis, in particular the use of THC-containing products. 

An earlier study conducted by researchers with the University of Sydney has delivered similar conclusions. That study included 26 healthy participants who were exposed to various cannabis products and were then engaged for 60-mile drive in real-world controlled conditions, including a 40-minute ride on a public highway.  

Intoxication was correlated with driving impairment in those participants who were exposed to THC during the study, while those who only received CBD did not experience any effect on their ability to drive. 

The math is simple: don’t drink or get exposed to THC if you are about to drive later on. Intoxication puts you at risk, as well as other people on the road at risk. 

Also read on Soft Secrets: 

- CBD Does Not Impair Driving, Landmark Study Shows

- The Entourage Effect in Cannabis

What Are Cannabis Edibles?

Stephen Andrews