(1) Those which are screened by natural objects, plantings, fences, or other appropriate means or which are otherwise removed from sight so as not to be visible from the main traveled way of such highway systems;
(2) Those located within areas which are zoned for industrial use under authority of law;
(3) Those located within unzoned industrial areas, which areas shall be determined from actual land uses and defined by regulations promulgated by the commissioner; and
(4) Those which are not visible from the main traveled way of the systems.