RCW 47.48.050: Transportation of radioactive or hazardous cargo—Definition—Violation, penalty.

The chief or other officer of the Washington state patrol may prohibit the transportation of placarded radioactive or hazardous cargo over the highways of the state, or a portion thereof, if weather or other conditions create a substantial risk to public safety. For the purposes of this section hazardous cargo shall mean hazardous materials as defined in RCW 70.136.020(1). Violation of an order issued under this section constitutes a misdemeanor.