Stoned drivers in Washington state are most likely to get in crashes between 4 and 5 p.m. and on Saturdays, according to a recent study of Washington State Patrol data conducted by a Seattle personal-injury law firm.

The analysis by the Davis Law Group also showed that stoned drivers in Vancouver, Clark County, are more likely to be involved in collisions than stoned drivers in any other city in the state, including Seattle, Tacoma and Spokane.

Where collisions involving stoned drivers happened most often in Washington state between 2015 and 2018, according to an analysis of Washington State Patrol data
Where collisions involving stoned drivers happened most often in Washington state between 2015 and 2018, according to an analysis of Washington State Patrol data

The law firm analyzed information collected and reported by the State Patrol from 2015 to 2018. According to its findings, released last month, only one person — a 19-year-old Snohomish man — was involved in a collision while stoned on the “high holiday” of April 20 in any of the four years evaluated.

In Washington, it is illegal for people 21 and older to drive with more than 5 nanograms of active THC per milliliter of blood. People younger than 21 may not drive with any amount of THC in their blood.

It can take several hours after getting high to drop below the legal THC limit, and the amount of time it takes can vary based on factors such as body size, according to the state’s Liquor and Cannabis Board. Some people can be impaired with less than 5 nanograms per milliliter of blood, according to the board.

“If you are not sure whether you are impaired, do not drive!” the board’s website warns. “Call a taxi or use a designated driver.”

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Driving while under the influence of alcohol or drugs is a leading factor in traffic deaths in Washington state, according to the State Patrol.

A total of 392 marijuana-involved driving incidents were reported in the time period studied, according to the Patrol’s statistics. Of those, 37 resulted in a death, 22 caused serious injury to at least one person, 110 resulted in minor injuries, and in 215 cases, no injuries were reported. There were unknown injuries in eight of the reported collisions, according to the Davis Law Group’s analysis.

The majority of the collisions reported involved two vehicles, followed by single-vehicle crashes, according to the report. About one-quarter of the crashes reported occurred at intersections.

Interstate 5 led the state’s roadways as the site of most weed-involved crashes, followed by I-90 and I-82 in Central Washington, the analysis found.

“The consequences of driving while stoned are just as severe as drunk driving,” said Matt Jones of the Davis Law Group.

Lt. Bruce Maier of the state patrol’s Impaired Driving Section said that since cannabis was legalized in the state in 2012, troopers have seen a steady increase in the number and percentage of weed-impaired drivers.

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In 2011, 20 percent of impaired drivers tested positive for THC, the principle psychoactive component of cannabis.

By 2017, that had risen to 44 percent, Maier said.

While impaired driving experts have said that the average person can metabolize about one alcoholic drink per hour, there is no such similar guidelines for cannabis, Maier said.

That’s because cannabis is processed differently than alcohol by the body and Maier said guidelines are harder to issue.

“It’s more conditional and complicated,” he said.

In addition, he said, the majority of impaired drivers these days are tend to test positive for more than one intoxicant.

“Some chronic cannabis users think that if they drink alcohol and then smoke out, they are better drivers,” he said. “That’s not how it works.”