As used in this part only, the following definitions apply:
(1) "Interstate system" means that portion of the national system of interstate and defense highways located within this state as officially designated or as may hereafter be so designated by the state transportation commission and approved by the secretary of transportation pursuant to the provisions of Title 23, United States Code, "Highways".
(2) "Junk" means old or scrap copper, brass, rope, rags, batteries, paper, trash, rubber debris, or waste; iron, steel, and other old or scrap ferrous or nonferrous material.
(3) "Junkyard" means any establishment or place of business which is maintained, operated, or used for storing, keeping, buying, or selling junk, excluding a motor vehicle graveyard or motor vehicle wrecking facility which is regulated under Title 75, chapter 10, part 5, and excluding a garbage dump or sanitary landfill which is regulated under Title 75, chapter 10, part 2.
(4) "Primary system" means that portion of connected main highways as officially designated or as may hereafter be so designated by the commission and approved by the secretary of transportation pursuant to the provisions of Title 23, United States Code, "Highways".