(a) In any year in which the General Assembly appropriates by line item, and with reference to this Code section, funds necessary to provide grants to counties to aid in the construction and maintenance of county roads, such grants shall be allotted to each county pro rata according to each county's share of the total number of homesteads in the state for the immediately preceding year.

(b) In order to provide better fiscal management, the funds provided pursuant to this Code section are intended to be utilized for the relief of ad valorem taxation on tangible property. No county shall be entitled to receive any of the funds provided for in this Code section unless and until a credit against county ad valorem property taxes levied and expended by the county governing authority is granted by the governing authority of the county to all eligible tangible property, as defined in subsection (c) of this Code section, except motor vehicles and trailers, located within the county. Each credit shall equal an amount computed as follows: a pro rata share of the sum of the grant allotted, pursuant to this Code section, to the county to aid in the construction and maintenance of county roads and the surplus, if any, from the funds allotted to such county by subsection (a) of Code Section 36-17-21, after compliance by the county with the provisions of subsection (b) of Code Section 36-17-21.

(c) As used in this Code section, the term "eligible tangible property" means all tangible property except that tangible property required to be returned to and assessed by the state revenue commissioner pursuant to statutes passed by the General Assembly under the authority of Article VII, Section I, Paragraph III of the Constitution of Georgia.