The Department may construct Federal-aid secondary or feeder highways, including farm-to-market roads, on such highways or sections of highways as may be necessary to comply with Federal-aid statutes and governing regulations of the Federal Highway Administration with respect thereto, regardless of whether, at the time of construction, such highways are in the State highway system. For the purposes of this section the Department may participate in the cost of construction of roads which are not in the State highway system in the same manner as is provided by law for construction of roads which are in the State highway system.
S.C. Code § 57-5-740