Clear Rule

The rules around marijuana use can be confusing. But when it comes to marijuana use and driving, all you need to remember is one clear rule:

Driving impaired is illegal everywhere.

Driving impaired is illegal everywhere.

Everything else can get kind of hazy.

When you feel different, you drive different. Everything else can get kind of hazy. So, if you want to think through some of the things experts and leading researchers are learning about marijuana’s effect on your driving, you can do that here.
Index
Issue
3
THC and Impairment
Subject

Unlike alcohol, the THC concentration level in the blood does not correlate with driver impairment.

Why it matters?

Alcohol-impaired driving has been a subject of intense interest and research for well over 60 years. When we compare the effects of consuming alcohol on behavior, attention, and cognition, we find that impairment in these functions strongly relates with alcohol concentration in blood or breath. Impairment increases with rising alcohol concentration and declines with dropping alcohol concentration.

While fewer studies have examined the relationship between THC blood levels (the psychoactive ingredient in marijuana) and degree of impairment, in those studies that have been conducted, the consistent finding is that the level of THC in the blood and the degree of impairment do not appear to be closely related. Unlike alcohol, there is no correlation between rising THC level and driver impairment. Some research studies have found that peak performance deficits are observed long after the peak THC level occurs.

Clarity Level
Medium
Abstract
This report describes the effects of THC vs. alcohol on the human body; the challenges of measuring driving impairment resulting from marijuana use; and the crash risk associated with marijuana impaired driving.
Abstract
This report describes the effects of THC vs. alcohol on the human body; the challenges of measuring driving impairment resulting from marijuana use; and the crash risk associated with marijuana impaired driving.
This ranking indicates how “settled” we feel an issue is. Issues that are clear-cut, fully-researched, and conclusive have a “High” clarity level. Issues that are involved in ongoing research, or focus on matters that require additional study, have “Medium” or “Low” clarity levels — depending on the amount and strength of supporting research.