40-14-5.
(a) Each state, county, municipal, or campus law enforcement officer using a radar device shall test the device for accuracy and record and maintain the results of the test at the beginning and end of each duty tour. Each such test shall be made in accordance with the manufacturer´s recommended procedure. Any radar unit not meeting the manufacturer´s minimum accuracy requirements shall be removed from service and thereafter shall not be used by the state, county, municipal, or campus law enforcement agency until it has been serviced, calibrated, and recertified by a technician with the qualifications specified in Code Section 40-14-4.
(b) Each county, municipal, or campus law enforcement officer using a radar device shall notify each person against whom the officer intends to make a case based on the use of the radar device that the person has a right to request the officer to test the radar device for accuracy. The notice shall be given prior to the time a citation and complaint or ticket is issued against the person and, if requested to make a test, the officer shall test the radar device for accuracy. In the event the radar device does not meet the minimum accuracy requirements, the citation and complaint or ticket shall not be issued against the person, and the radar device shall be removed from service and thereafter shall not be used by the county, municipal, or campus law enforcement agency until it has been serviced, calibrated, and recertified by a technician with the qualifications specified in Code Section 40-14-4.

40-6-183.
(a) Whenever the governing authority of an incorporated municipality or county, in its respective jurisdiction, determines on the basis of an engineering and traffic investigation that the maximum vehicle speed permitted under this chapter is greater than is reasonable and safe under the conditions found to exist upon a highway or part of a highway under its jurisdiction, such authority may determine and declare a reasonable and safe maximum vehicle speed limit thereon which:
(1) Decreases the limit at intersections;
(2) Decreases the limit outside an urban or residential district, but not to less than 30 miles per hour;
(3) Decreases the limit within an urban or residential district, but not to less than 25 miles per hour; or
(4) Decreases any speed limit where a special hazard or condition exists that requires lower speed for compliance with Code Section 40-6-180.
(b) Such an authority in its respective jurisdiction shall determine by an engineering and traffic investigation the proper maximum speed for all arterial streets and shall declare a reasonable and safe maximum speed limit thereon which may be greater or less than the maximum speed permitted under this chapter for an urban district, but in no case shall the maximum be established at higher than 55 miles per hour.
(c) Any altered limit established as authorized in this Code section shall be effective at all times or during hours of darkness or at other times as may be determined when appropriate signs giving notice thereof are erected upon such street or highway.
(d) Not more than six alterations as authorized in this Code section shall be made per mile along a street or highway, except in the case of reduced limits at intersections. The difference between adjacent limits shall not be more than ten miles per hour, except for reductions for school speed zones, which may be not more than 20 miles per hour when a warning sign is placed 700 feet in advance of the point at which the speed reduction is required.

40-6-182.
Whenever the commissioner of public safety or the commissioner of transportation shall determine upon the basis of an engineering and traffic investigation that any maximum speed set forth in this article is greater or less than is reasonable or safe under the conditions found to exist at any intersection or other place or upon any part of the state highway system, they may jointly determine and declare a reasonable and safe maximum speed limit at such place, which shall be effective when appropriate signs giving notice thereof are erected. Such a maximum speed limit may be declared to be effective at all times as are indicated upon such signs; and differing limits may be established for different times of day, different varying weather conditions, and other factors bearing on safe speeds, which shall be effective when posted upon appropriate fixed or variable signs. In no case shall the maximum speed limit for any highway be established at higher than the maximum speed limits set forth in Code Section 40-6-181 for that type of highway.