As states across the country, and surrounding Virginia, adjust the laws concerning marijuana, more people are focused on how this could affect the rules of the road. As the Washington Post explains, this is a complicated issue without a consensus among law enforcement.
If a person is pulled over for suspected driving under the influence, due to haphazard driving or other behavior the officer considers suspicious, he or she will administer a field test to check for sobriety. Yet unlike drinking and driving, there is not an equivalent test to a breathalyzer to measure how much marijuana is in a person’s system. In fact, while a blood test can determine how much THC is in one’s blood, there is not an agreement across the country for what level is acceptable while driving. This may be because depending on the method a person uses to get high, smoking versus edibles, his or her level of THC would differ.
As Time reports, while the nationwide standard for drunk driving is a breath alcohol concentration of .08, there is not a similar limit for THC. Washington and Colorado have decided that 5 ug/L of THC in the blood is their legal limit, but without a roadside test, some believe that limit is too high, as it means the person being tested had a considerably higher THC level while driving. While marijuana and alcohol affected drivers differently, combining the two could impair drivers who were below the legal limits. Taken together, alcohol and marijuana also increase the absorption of THC while delaying the effects of alcohol, so a person who smoked and drank would feel more drunk and high for a longer amount of time.