Wash. Rev. Code § 47.12.250
The department is authorized to acquire by purchase, lease, condemnation, gift, devise, bequest, grant, or exchange, title to or any interests or rights in real property adjacent to state highways for the preservation of natural beauty, historic sites or viewpoints or for safety rest areas or to provide a visual or sound buffer between highways and adjacent properties. However, the department shall not acquire, by condemnation, less than an owner's entire interest for providing a visual or sound buffer between highways and adjacent properties under RCW 47.12.010 and 47.12.250 if the owner objects to the taking of a lesser interest or right.
RCW 47.12.250
Roadside areas-Safety rest areas: Chapter 47.38 RCW.
Scenic and Recreational Highway Act: Chapter 47.39 RCW.