All 50 states and the District of Columbia prohibit the operation of a motor vehicle while under the influence of intoxicating beverages, with the illegal per se limit set at 0.08 percent blood alcohol concentration (.08 BAC). All 50 states and the District of Columbia set the legal drinking age at 21.
Washington law specifies that drivers with 5 nanograms of active tetrahydrocannabinol (THC) in their whole blood can be prosecuted for driving under the influence.
Every state’s chemical test law has ‘‘an implied consent’’ provision providing that any person operating a motor vehicle on a public highway, who is suspected of driving while intoxicated, consents to a chemical test to determine if he or she is inebriated. Failure to submit or pass such a test may cause the driver’s license to be suspended or revoked regardless of any court action finding the person innocent of the charge.
The most comprehensive resource on U.S. impaired driving laws is the National Highway Traffic Safety Administration’s Digest of Impaired Driving and Selected Beverage Control Laws. NHTSA’s Digest is updated annually.
Washington requires the use of ignition interlocks for all impaired driving offenders.
Washington has an illegal per se limit for marijuana set at 5 ng/mL active THC.