Driving while impaired by drugs or alcohol is well known to be extremely dangerous, and in some cases, fatal. But what about marijuana?

Does marijuana impair driving?

The problem with testing the effects of driving while under the influence of marijuana is that the substance responsible for getting you high, THC, can stay in your system for a very long time, especially for chronic users. People involved in car accidents with THC in their system may have used the substance the same day of the accident, or even a month ago. That being said, certain studies have shown a correlation between blood THC concentration and impaired driving.

Marijuana users seem more aware of their impairment

The use of marijuana impairs plenty of cognitive abilities needed for safe driving. Among the list of skills affected by the use of the drug are divided attention, visual function, tracking, and motor coordination. Some studies show that marijuana users can compensate for their impairments, unlike those driving under the influence of alcohol. Most of the time, drivers under the influence of marijuana seem to follow cars at greater distances and travel at lower speeds.

It’s just like being drunk

Users of marijuana experience similar impairment as drunk drivers when their blood reaches 13 micrograms of THC per liter of blood. The legal limit in states where both medicinal and recreational use is legalized, like Oregon and Washington, is 5 micrograms per liter of blood. Obviously, the higher you are, the risk of being involved in an auto accident increases immensely. The effects of marijuana are greatest during the first hour after use.

Marijuana + alcohol = more danger

The use of marijuana and alcohol in combination raises the risks of driving drastically. The problem with drug use, legal or illegal, is that consumption is usually accompanied with drinking. Combining marijuana and the effects of alcohol, which is a depressant, slows reaction rates immensely and is more likely to result in an accident than if a driver uses one of either substance on its own.

More evidence needed

With the popularization of marijuana legalization, several scientific studies have been dedicated on understanding the effects of driving while under its influence. Although it is sure that driving after smoking or consuming the substance is not a good idea, it is difficult to state the exact effect on drivers at the moment. Studies have shown that when consumed in low doses, marijuana does not make a huge difference in drivers. These studies show evidence of impairment, but do not necessarily state that the level of impairment is high enough to affect performance levels behind the wheel.