Any junkyard, or automotive dismantler and recycler lawfully in existence on January 1, 1967 which is within one thousand feet of the nearest edge of the right-of-way of a highway, and which is not in any of the classes specified in subsections (b), (c) and (d) of section 4¹ shall be screened, if physically and economically feasible, by the secretary at locations on the highway right-of-way or in areas acquired for such purposes outside the right-of-way, so as not to be visible from the main-traveled way of the highway. No junk or any other motor vehicle incapable of meeting State inspection requirements shall be placed between the highway and the screening.