(a) Definitions; registration required. As used in W.S. 31-18-203 through 31-18-208: (i) "Mobile machinery" means heavy equipment, except shop or hand tools or attachments, which is self-propelled, towed or hauled and used primarily in construction and maintenance of roads, bridges, ditches, buildings or land reclamation; (ii) The definitions in W.S. 31-1-101 apply in this (iii)