Whenever the board of supervisors finds that any road district in such county is or will be unreasonably burdened by the expense of constructing or maintaining any county highway, or any bridge or tunnel connecting or forming a part of such highway, or by the expense of the purchase of any toll roads the board may:
(a)
Order the whole or any portion of the aggregate expense to be paid out of the road fund of the county.
(b)
By a majority vote of the board’s membership, order the whole or any portion of the expense of construction or repair of such bridges or tunnels, or a portion of the expense of the purchase of such toll roads, to be paid out of the county general fund.
(c)
By unanimous vote of the board’s membership, order the whole or any portion of the expense of material for highway construction to be paid out of the county general fund.
(d)
By a four-fifths vote of the board’s membership, order to be paid out of the county general fund or the road fund, or both, the whole or any portion of the expense of constructing, reconstructing or repairing any bridges or highways destroyed or damaged by storms, floods or calamities.