Any junkyard lawfully in existence on May 4, 1966, which is within one thousand feet of the nearest edge of the right-of-way and visible from the main traveled way of any federal-aid or state highway shall be screened, if feasible, by the department of transportation 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; provided that if such a junkyard is located in an area zoned for industrial use, the requirement for screening shall not apply.