Section 28-301 - Transportation districtsA. Except as provided in subsection B, the state is divided into six transportation districts as follows:1. First district, Maricopa county.2. Second district, Pima county.3. Third district, Cochise, Greenlee and Santa Cruz counties.4. Fourth district, Gila, Graham and Pinal counties.5. Fifth district, Apache, Coconino and Navajo counties.6. Sixth district, La Paz, Mohave, Yavapai and Yuma counties.B. If, after January 1, 2009, a county attains a population of five hundred thousand or more persons, a new district shall be formed consisting of only that county. The county shall be removed from the district it was in before the new district was formed. The clerk of the county board of supervisors, with the concurrence of the Arizona commerce authority, shall notify the governor, the state transportation board and the department of transportation of the new district by the end of the calendar year in which the county becomes qualified under this subsection. The governor shall appoint an additional member of the state transportation board for the new district pursuant to this section within sixty days after receiving the notice.