Nothing herein shall prevent an owner of land from using, or permitting the use of, his land for outdoor advertising purposes where said owner’s land abuts a highway parallel to, or nearly parallel to and less than 660 feet from the edge of right-of-way of an interstate, federal aid primary or turnpike highway provided that the advertising or informative contents of advertising devices erected and maintained on said land shall not be visible from the main traveled way of an interstate, federal aid primary or turnpike highway.