In counties which have heretofore created special or general road funds under then existing laws, the boards of supervisors may use such funds as if originally collected hereunder. In case the board of supervisors shall, in availing themselves of this provision, relieve from the operation of the contract system any part of a county entitled to a special fund, the board may also order that such special fund shall become a part of the general fund.
Miss. Code § 65-15-17