Is marijuana related to car crashes going up in Washington State?

Since Washingtons State approved recreational use of marijuana, we have watched to see how it would affect drivers and road safety.


A study completed by the Highway Loss Data Institute found an uptick in car crash claims in Colorado, Oregon and Washington.

Read the HLDI Study bulletin: Recreational marijuana and collision claim frequencies.

Increase in car crash claims from 2012-2016: 

  • Colorado: 13.9%
  • Washington: 6.2%
  • Oregon: 4.5%

“We see strong evidence of an increased crash risk in states that have approved recreational marijuana sales.”

Matt Moore, HLDI senior vice president 

It’s not surprising that legalizing marijuana would result in more crashes* caused by drivers who were high. Safety advocates, law enforcement, and others have speculated on how legalizing marijuana related to car crashes.

* We don’t think predictable, preventable crashes caused by stoned drivers are “car accidents”: Say Crash, Not Accident

But, there isn’t actually enough data to study whether or not the increase in collision claims in Washington, Oregon and Colorado were directly caused by marijuana-impaired drivers.

And, that data probably won’t exist soon: there’s no consensus on measuring marijuana impairment

There are several methods, but states have not come to a consensus on measuring marijuana impairment.

Both Colorado and Washington have set a legal limit of 5 nanograms of THC in the bloodstream. A driver whose THC level exceeds 5 ng/ml is considered impaired. In Oregon, there is no legal limit for marijuana-impaired driving.

A study by AAA’s safety foundation says the legal THC limits have no scientific basis.

And, there is not a field sobriety test to check drivers specifically for marijuana (yet). 

That is not to say that driving while high on marijuana isn’t dangerous. 

Anything that impairs your driving is dangerous. 

Driving under the influence of marijuana about doubles your likelihood of a car crash, according to Mark Kleiman, an NYU professor specializing in drugs and criminal policy.

He notes that driving with “a noisy child in the back of the car” is about as dangerous as using marijuana and driving, and points out the danger of other impairments. 

4x more likely to crash: Talking on a hands-free cellphone while driving—which is legal in most states. 

5x more likely to crash: Drivers who have slept less than 5 hours, compared to those sleeping 8+ hours. 

15x more like to crash: Driving with a blood alcohol content of .12 —about the average BAC in drunk driving cases. 


More than 39,000 Americans died in car crashes last year.

Most of these were predictable, preventable deaths. They cost almost $1 trillion in loss of productivity, and loss of life. They caused untold pain and terrible repercussions to families and friends. 

Whether or not marijuana is related to car crashes – driving is likely the most dangerous thing you do on a regular basis.  

Take it seriously.



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