No portion of a license fee paid as aforesaid will be refunded for any part of the year during which the license is not used except that when any carrier is prohibited from operating over his route by virtue of the closing of any road by the State, county, city or town authorities, there shall be a proper readjustment and credit given such operator proportionately for such unused portion of his license, unless a passable detour is provided.
S.C. Code § 58-23-610