As medical and recreation marijuana begin to become legal in more states across the country, safety officials have begun to look more closely at the impacts of marijuana use on driving.
Although instinctively we are inclined to assume that marijuana significantly increases the risk of being involved in a car accident, the truth is that the studies do not necessarily support that conclusion. In fact, after adjusting for demographics and whether a driver had also consumed alcohol, one study found no increased risk of crash associated with marijuana use. The author cautioned jumping to conclusions too quickly, noting that he still believed that there was a risk associated with driving under the influence of marijuana but that it was not as great as originally expected.
Marijuana and alcohol effect the body in very different ways and as a result the impact on a driver’s skills and reaction times are also different. For example, drunk drivers typically tend to go faster than the speed limit, overestimating their ability to react quickly to a hazard. Stoned drivers do the opposite, driving more slowly and cautiously.
These different effects are also mirrored in the ability of a drunk driver versus a stoned driver to pass a field sobriety test, which looks at balance, hand-eye coordination, and vision. Field sobriety testing has about an 88 percent success rate at detecting a drunk driver, whereas a stoned driver fails only 30 percent of the time.
What does this mean for DUI laws? Well, it means that researchers and law enforcement officers must continue to gather more information before implementing marijuana-specific DUI regulations. It also means that relying on conventional wisdom might not actually improve safety on the roads. For drivers who are apprehended and found to have THC in their system, it means fighting back against the assumption that they were impaired to the point that they were unfit to be on the road.
Source: New York Times, “Driving Under the Influence, of Marijuana,” Maggie Koerth-Baker, Feb. 17, 2014.