With Labor Day weekend behind us, law enforcement agencies in Washington will presumably scale back its stepped-up efforts to stop drivers who they believe are impaired. But the question over how pot affects motor vehicle operation continues; and an Associated Press article discussing this debate appeared in publications across the country this week.
The piece reveals the large amount of conflicting information on this topic by highlighting two recent studies. One was a roadside survey conducted by Columbia University, and it found that marijuana by itself increased the prevalence of being involved in a fatal crash by 80%. However, these results could have been skewed by the use of urine tests versus blood tests, as well as a failure by many states in the study to test for both alcohol and drugs.
The Pacific Institute for Research and Evaluation also evaluated the roadside survey data while including additional information from nine other states. These researchers found that when the results were adjusted for driver demographics as well as alcohol, drivers who tested positive for marijuana (but not alcohol) were a bit less likely to be in a fatal crash than those who were completely sober.
The standard for DUI Washington is five nanograms of active THC per milliliter of blood equivalent. But some studies indicate that longtime marijuana users might develop a tolerance and therefore not be impaired by that amount of THC. It's clear that more research is necessary on the correlation between pot and driving impairment. Let's hope that as more information becomes available, Washington and other states will adjust their DUI rules and standards accordingly.