Wash. Rev. Code § 47.52.040
The highway authorities of the state, counties and incorporated cities and towns may so design any limited access facility and so regulate, restrict, or prohibit access as to best serve the traffic for which such facility is intended; and the determination of design by such authority shall be conclusive and final. In this connection such highway authorities may divide and separate any limited access facility into separate roadways by the construction of raised curbings, central dividing sections, or other physical separations, or by designating such separate roadways by signs, markers, stripes, and the proper lane for such traffic by appropriate signs, markers, stripes and other devices. No person shall have any right of ingress or egress to, from, or across limited access facilities to or from abutting lands, except at designated points at which access may be permitted by the highway authorities upon such terms and conditions as may be specified from time to time: PROVIDED, That any intersecting streets, roads or highways, not made a part of such facility, shall be deemed closed at the right-of-way line by the designation and construction of said facility and without the consent of any other party or the necessity of any other legal proceeding for such closing, notwithstanding any laws to the contrary.
RCW 47.52.040