Georgia Code Title 32. Highways, Bridges, and Ferries § 32-4-1

(1) STATE HIGHWAY SYSTEM.The state highway system shall consist of those public roads which on July 1, 1973, are shown by the records of the department to be “state-aid roads,” those public roads thereafter designated by the department as part of the state highway system, and all of The Dwight D. Eisenhower System of Interstate and Defense Highways within the state;

(2) COUNTY ROAD SYSTEMS.Each county road system shall consist of those public roads within that county, including county roads extending into any municipality within the county, which are shown to be part of that county road system by the department records on July 1, 1973, and any subsequent additions to such county road system made by the county;

(3) MUNICIPAL STREET SYSTEMS.Each municipal street system shall consist of those public roads within the limits of that municipality which are not in any other classification under this Code section.