Does legal marijuana cause deadly car wrecks? Numbers tell a story

Larry Heiny of Sarasota rallies the crowd after a USF medical marijuana rally in Tampa in 2014.
Larry Heiny of Sarasota rallies the crowd after a USF medical marijuana rally in Tampa in 2014. AP

After Washington state legalized pot, fatal car crashes involving drivers who recently used marijuana more than doubled, according to new research released by the AAA Foundation for Traffic Safety.

The foundation — a nonprofit created by AAA, which provides emergency roadside service to drivers — found that 17 percent of Washington drivers involved in fatal crashes in 2014 had used marijuana recently. That figure was more than double the eight percent of drivers who had marijuana in their system in 2013.

Does that mean marijuana caused the fatal crashes? Not necessarily.

The AAA definition of “recent” marijuana use included all drivers who tested positive for marijuana on blood tests, and AAA spokesman Matt Nasworthy said “they could have used marijuana the day prior, and still have it showing up in their system.”

“It is a fuzzy number,” Nasworthy said of the 17 percent figure.

Washington voters legalized marijuana at the end of 2012. Nearly 58 percent of Florida voters supported legalizing medical marijuana in 2014 — just shy of the 60 percent needed to get the constitutional amendment approved.

Florida voters will again decide whether to legalize medical marijuana in November. A recent poll of Miami-Dade County voters found 61 percent support legalization, with 36 percent opposed and three percent undecided.

Public safety concerns will almost certainly be part of the political debate leading up to Florida’s November vote. In announcing its new research findings this week, AAA noted that the organization “does not take a position” on the legalization of marijuana.

In a statement, Kevin Bakewell, Senior Vice President and Chief Public Affairs Officer for AAA – The Auto Club Group, said “our advice is that nobody should drive after recent marijuana use, and law enforcement should have a fair and educated approach for dealing with those who do.”

Measuring whether a marijiana user is too high to drive isn’t easy, AAA found. While drunk drivers can be arrested for exceeding the .08 blood-alcohol level, AAA researchers said there is no similarly objective way to measure whether a driver is impaired by smoking pot.

“Current science shows that drivers do not reliably become impaired at a specific level of marijuana in the blood,” AAA wrote in announcing its findings. “Depending on the individual, drivers with low levels of THC in their blood may be unsafe behind the wheel, while others with relatively high levels might not be impaired.”

AAA found that it is “problematic” when states create specific THC limits to determine whether a marijuana user is too high to drive, as the hours-long delays in obtaining a blood sample can make the results less reliable. Also, frequent users of marijuana may have THC in their system long after the high has worn off.

AAA’s recommendation: a two-pronged test where law enforcement considers the results of a blood test but is also trained to recognize “behavioral and physiological evidence of driver impairment.”