As used in sections 168.841 to 168.846, “rental truck” means a truck or truck-tractor and “rental trailer” means a trailer or semitrailer as these terms are defined in section 168.002, which is one of a fleet of two or more such vehicles owned and operated for hire for periods of 30 days or less both within and without the state of Minnesota, which are clearly identified as belonging to a particular owner, and which are not otherwise required to be registered in the state.