Wash. Rev. Code § 46.44.098
If the congress of the United States further amends section 127, Title 23 of the United States Code, authorizing increased sizes and weights, the Washington state department of transportation may authorize the operation of vehicles and combinations of vehicles upon completed portions of the interstate highway system and other designated state highways if determined to be capable of accommodating the increased sizes and weights in excess of those prescribed in RCW 46.44.041, or as provided in RCW 46.44.010 and 46.44.037. The permitted increases shall not in any way exceed the federal limits which would jeopardize the state's allotment of federal funds.
RCW 46.44.098
Effective dates-Severability-1975-'76 2nd ex.s. c 64: See notes following RCW 46.16A.455.