(1) Except as otherwise provided in subsection (3) of this section, just compensation shall be paid upon the removal of any sign (pursuant to the provisions of chapter 47.42 RCW), lawfully erected under state law, which is visible from the main traveled way of the interstate system or the primary system.
(2) Such compensation shall be paid for the following:
(a) The taking from the owner of such sign, display, or device of all right, title, leasehold, and interest in such sign, display, or device; and
(b) The taking from the owner of the real property on which the sign, display, or device is located, of the right to erect and maintain such signs, displays, and devices thereon.
(3) In no event, however, shall compensation be paid for the taking or removal of signs adjacent to the interstate system and the scenic system which became subject to removal pursuant to chapter 96, Laws of 1961 as amended by section 55, chapter 3, Laws of 1963 ex. sess. prior to May 10, 1971.