Provides that a person may not drive, operate, or be in physical control of a commercial motor vehicle with the presence of any Schedule I drug, as listed in RCW 69.50.204, or its metabolite, or Schedule II drug, as listed in RCW 69.50.206, or its metabolite, in his or her blood and be involved in a motor vehicle accident in which there is: (1) A human fatality;

(2) Bodily injury to any person who, as a result of the injury, immediately receives medical treatment away from the scene of the accident; or

(3) One or more motor vehicles that incur disabling damage as a result of the accident, requiring the motor vehicle to be transported away from the scene by a tow truck or other motor vehicle.

Declares that it is an affirmative defense to a violation of this act, which the defendant must prove by a preponderance of the evidence, that the defendant had a valid prescription for any controlled substance consumed, and that the defendant consumed the controlled substance according to the prescription's directions and warnings.