There has been a 49-percent increase in the rate of positives for marijuana among drivers stopped by State Troopers for suspicion of Driving Under the
Influence in the first six months of 2013 in the State of Washington. In the brain, cannabinoid receptors are found in large concentration in areas that influence memory, thought, concentration, sensory and time perception, and coordination. Depth perception, coordination, and concentration are all required to safely drive a car or operate machinery.
A 2011 study entitled Marijuana Use and Motor Vehicle Use found that “crash risk appears to increase progressively with dose and frequency of marijuana use.” Key study findings included that “drivers who test positive for marijuana or self-report using marijuana are more than twice as likely as other drivers to be involved in motor vehicle crashes.”
Another study of more than 64,000 insured drivers from 1979-1985 found that 31 percent of drivers involved in motor vehicle crashes reported smoking marijuana prior to the accident.