WASHINGTON — Fatal crashes involving marijuana use in Washington doubled after the state legalized the substance, according to the latest research from the AAA Foundation for Traffic Safety.
For the AAA study, researchers reviewed the cases of more than 3,000 Washington drivers who were involved in fatal vehicle crashes from 2010 to 2014 and found that the proportion of those drivers with traces of marijuana in their systems rose from 8 percent to 17 percent between 2013 and 2014.
In December 2012, Washington became one of the first two U.S. states to legalize the recreational use of marijuana. There are now four, plus another 20 that have legalized it for medicinal use.
"The significant increase in fatal crashes involving marijuana is alarming," said Peter Kissinger, president and CEO of the AAA Foundation for Traffic Safety, in a statement. "Washington serves as an eye-opening case study for what other states may experience with road safety after legalizing the drug."
In a separate study, the AAA Foundation examined the lab results of drivers arrested for impaired driving and found that the legal limits imposed by many states for THC (the main psychoactive ingredient in marijuana) in a driver's bloodstream may not be adequate to ensure the ability to operate a vehicle safely.
Among other findings, the study determined that, unlike alcohol, there is no specific level at which THC clearly impairs a driver; THC levels can drop off significantly by the time a blood test is administered; and marijuana affects people so differently that it's difficult to develop fair and consistent guidelines.
"There is understandably a strong desire by both lawmakers and the public to create legal limits for marijuana impairment, in the same manner as we do with alcohol," said Marshall Doney, AAA's president and CEO. "In the case of marijuana, this approach is flawed and not supported by scientific research. It's simply not possible today to determine whether a driver is impaired based solely on the amount of the drug in their body."
Rather than strict numerical limits — called per se limits — AAA says it is urging states to determine THC impairment using a combination of blood tests and field sobriety tests by trained law-enforcement officers.
This specialized training, AAA suggests, can be provided by two current programs: the Advanced Roadside Impaired Driving Enforcement (ARIDE) and the 50-state Drug Evaluation and Classification (DEC) program.
Edmunds says: This study points out both a problem and the need to rethink how impaired driving is defined.