S.C. Code § 57-5-90
The commission may establish such belt lines or spurs as it deems proper and construct and maintain such belt lines and spurs from funds otherwise provided by law for the construction and maintenance of the state highway system, but the total length of such belt lines and spurs to be established or constructed in any county shall not exceed two miles in any one fiscal year; provided, that should the commission fail to establish belt lines or spurs during a fiscal year the allocation to the counties shall be continued from year to year and the mileage shall be cumulative. Provided, further, that any mileage that accumulated prior to June 30, 1972, under this section shall remain to the credit of the county to which it accumulated.
S.C. Code § 57-5-90