Iowa Code § 321.443: Special permits authorized.

The department and local authorities in their respective jurisdictions shall review any application for a special permit and may, with good cause being shown, issue special permits authorizing the operation upon a highway of traction engines or tractors having movable tracks with transverse corrugations upon the periphery of such movable tracks or farm tractors or other farm machinery, the operation of which upon a highway would otherwise be prohibited under this chapter.