It is unlawful to operate without a special permit on public highways a combination of a tractor and two trailers with a combined length of the trailers of more than 61 feet in length. Operators of overlength vehicles must obtain a special permit from the Washington State Department of Transportation (WSDOT) to travel on the state highway system. Typically overlength permits are granted for loads that cannot be easily dismantled or divided, or nondivisible loads. Valid permits that are issued may range from one day to one year.
The WSDOT is authorized to issue a one-year permit for operation of two trailing units which together are no more than 68 feet in length. The WSDOT must charge a $100 fee for the permit.
The Fixing America's Surface Transportation Act (FAST Act) reauthorized federal surface transportation programs in 2015, and included a provision (Section 1409) that required that a vehicle carrying fluid milk products must be considered a nondivisible load.
The WSDOT is authorized to issue a one-year special permit for operation of two trailing units hauling fluid or liquid nondivisible milk, which together exceed 61 feet in length and are not more than 85 feet in length. The WSDOT must charge a $300 fee for the permit.