Over the past two decades a number of studies have been conducted regarding this concern by a variety of institutions including the U.S. Department of Transportation National Highway Traffic Safety Administration, the Canadian Senate Special Committee on Illegal Drugs, and the University of Iowa. Crash culpability, on-road performance, and driving simulator studies have suggested that recent consumption of cannabis may cause minor psychomotor deficiencies, altered perceptions of time, and a general “change” in a user’s perception but there has been little to no evidence to label marijuana use as a major and unavoidable “impairment”.
The United States NHTSA’s official “Drugs and Human Performance Fact Sheets” claims, “It is difficult to establish a relationship between a person’s THC blood or plasma concentration and performance impairing effects.
Concentrations of parent drug and metabolite are very dependent on pattern of use as well as dose…” and goes further to read “It is inadvisable to try and predict effects based on blood THC concentrations alone, and currently impossible to predict specific effects based on THC-COOH concentrations. It is possible for a person to be affected by marijuana use with concentrations of THC in their blood below the limit of detection of the method.” THC-COOH is also known as ‘carboxy THC’ and is the metabolite of THC most commonly tested for in blood as it shows up shortly after cannabis is consumed.
Despite this information a number of states have established strict limits on the number of nanograms of THC per milliliter that can be present in any person’s blood while driving.
Some of these states include Washington with a ‘per se limit’ of 5ng/ml, Colorado with a ‘reasonable inference’ law at 5ng/ml, and Pennsylvania with one of the strictest laws with a hard limit set at 1ng/ml. However, recently multiple new studies released by the American Automobile Association Foundation for Traffic Safety call into question the science and validity behind these laws.
By being a non-profit organization that is focused on providing millions of motorists through research and education the AAA Foundation is uniquely positioned to offer perspective on this situation and have in turn released the findings of recently commissioned studies along with their summaries online which include:
● “Prevalence of Marijuana Use among Drivers in Washington State”
● “An Evaluation of Data from Drivers Arrested for Driving Under the Influence in Relation to Per se limits for Cannabis”
● “Cannabis Use among Drivers Suspected of Driving Under the Influence or Involved in Collisions: Analysis of Washington State Patrol Data” and last but not least
● “Driving Under the Influence of Alcohol and Marijuana: Beliefs and Behaviors, Unites States, 2013-2015”
They also list two pieces of supporting research from earlier this year which include:
● Overview of Major Issues Regarding the Impacts of Alcohol and Marijuana on Driving
● Advancing Drugged Driving Data at the State Level: Synthesis of Barriers and Expert Panel Recommendations
Without going too far into detail there are two major findings reported by the AAA. First and foremost the number of fatal accidents in Washington State wherein marijuana was a contributing factor have doubled since the passing of I-502. Although quite alarming at first glance we need to be clear that these incidents are indicative of poly-drug use and not un-adulterated marijuana use specifically. This is not to downplay the seriousness of the given data but rather to approach the statistics properly and accurately. Secondly, AAA suggests firmly that, “Legal limits, also known as per se limits, for marijuana and driving are arbitrary and unsupported by science” and ultimately go on to propose driving infractions be issued to drivers caught under the effects of THC vs nailing them with a DUI.
We can only hope that these findings lead to more investigations and will further demystify the details surrounding the effects of cannabis and driving. It is clear that as it stands the current hard and per se limits imposed by a number of states are being brought into serious question but whether or not the public and legislatures will consider revising these scientifically unfounded laws remains to be seen.