The spreading acceptance of marijuana legalization has made patrolling the roads trickier.
Police in Washington are still trying to maneuver new laws regarding marijuana use and its ability to impair people while driving.
According to the Christian Science Monitor on Sunday, police have pulled over more drivers that test positive for cannabis than in the past.
Authorities reported that 745 people tested positive for THC, the psychoactive ingredient in marijuana, after being pulled over on the road.
Out of those, 420 people tested over the legal limit for the substance. Washington capped THC levels to 5 nanograms or less per milliliter of blood for drivers.
Washington passed legislation to allow a certain amount of recreational use of marijuana within the state. I-502 does not allow users to drive under the influence and has several restrictions about growing and selling of the substance.
"It was previously illegal to drive under the influence of marijuana and it remains illegal,” said Mastin Tvert, spokesperson for the Marijuana Policy Project according to the New York Daily News Sunday.
The amount of increased DUI charges has been attributed to the new law, but also to more police testing for the drug.
Anti-marijuana groups have used this information to justify attempts to ban marijuana and stop recreational cannabis stores from opening in the state.
"People are getting the impression that marijuana use is okay," Kevin Sabet of anti-cannabis group Priject Smart Approaches to Marijuana according to the Christian Science Monitor.
Police totaled nearly 20,000 cases per year of people being pulled over for suspicion of impaired driving.