S.C. Code § 11-43-550
For the payment of the principal of and interest on all transportation infrastructure bonds, whether or not outstanding or hereafter issued, as they come due, there is pledged the full faith, credit, and taxing power of this State, and in accordance with the provisions of Section 13(4), Article X of the Constitution of this State, the General Assembly authorizes the allocation on an annual basis of sufficient tax revenues to provide for the punctual payment of the principal and interest on transportation infrastructure bonds. In addition to the full faith, credit, and taxing power, there also is pledged such revenue as may be available to the board, and the State Treasurer is authorized to use such revenue when pledged, without further action of the board, for the payment of the principal and interest on transportation infrastructure bonds as the bonds respectively mature. If the revenues so pledged prove insufficient to meet the payments of the interest on and principal of the transportation infrastructure bonds in the fiscal year, then the State Treasurer shall set aside from the general tax revenues received in the fiscal year so much of the general tax revenues as are needed for the purpose and shall apply these revenues to the punctual payment of the interest on and principal of transportation infrastructure bonds due or to become due in the fiscal year.
S.C. Code § 11-43-550