Any junkyard lawfully in existence on September 8, 1971, which is located within 1,000 feet of the nearest edge of the right-of-way and visible from the main-traveled way of any highway on the interstate or primary system, shall be screened, if considered feasible by the director. The screening shall be at locations on the right-of-way or in areas outside the right-of-way acquired for such purposes, so as not to be visible from the main-traveled way of the interstate or primary system.