Wash. Rev. Code § 47.52.010
For the purposes of this chapter, a "limited access facility" is defined as a highway or street especially designed or designated for through traffic, and over, from, or to which owners or occupants of abutting land, or other persons, have no right or easement, or only a limited right or easement of access, light, air, or view by reason of the fact that their property abuts upon such limited access facility, or for any other reason to accomplish the purpose of a limited access facility. Such highways or streets may be parkways, from which vehicles forming part of an urban public transportation system, trucks, buses, or other commercial vehicles may be excluded; or they may be freeways open to use by all customary forms of street and highway traffic, including vehicles forming a part of an urban public transportation system.
RCW 47.52.010
Urban public transportation system defined: RCW 47.04.082.