Submitted by the Washington Traffic Safety Commission

Newly released data from the Washington Traffic Safety Commission shows that marijuana is increasing as a factor in deadly crashes. The number of drivers involved in deadly crashes who tested positive for marijuana increased 48 percent from 2013 to 2014.

“We have seen marijuana involvement in fatal crashes remain steady over the years, and then it just spiked in 2014,” said Dr. Staci Hoff, WTSC Data and Research Director.

From 2010-2014, nearly 60 percent of drivers involved in fatal collisions were tested for drugs. Among these tested drivers, approximately 20 percent (349 drivers) were positive for marijuana.

However, just testing positive for marijuana doesn’t necessarily indicate if a driver was actually affected by the drug at the time of the crash since marijuana can be detected in a person’s blood for days (possibly weeks) after a person uses the drug. This new data is able to distinguish between drivers who test positive for tetrahydrocannabnol, better known as THC, the impairing substance in marijuana and those who have residual marijuana in their system from prior use which may have occurred days ago.

The number of drivers testing positive for active THC has steadily increased, from less than half of marijuana positive drivers in 2010 up to almost 65 percent of drivers in 2013. In 2014, an alarming 85 percent (75 of 89 drivers) of drivers testing positive for marijuana were positive for impairing THC.

“With this data we are finally able to see who was high during the crash versus which drivers had used marijuana in the past few days,” said Hoff. “The answer in 2014 is most of them were high.”

Approximately half of these THC-positive drivers exceeded the 5 ng/ml THC per se limit. (A “per se” limit is the amount of a substance in a person’s blood that according to Washington law makes the person DUI notwithstanding other evidence.)