County roads; authority to regulate speed limits.

A. The board of county commissioners of a county may alter and establish speed limits lower than those established by law on county roads within its county, provided that: (1) the speed limit is deemed to be reasonable and safe under local conditions on the basis of an engineering survey and traffic investigation; (2) the alteration of a speed limit is approved by the state transportation commission; and (3) the county posts speed limit signs that conform to the specifications as set forth in the manual adopted by the state transportation commission before enforcing the speed limit. B. As used in this section, "county roads" means any streets, roads or highways built and maintained by the county or the control of which has been given to the county by the state transportation commission.