Each resolution providing for the issuance of revenue bonds shall provide for setting aside the necessary amounts for the reasonable and proper operation, maintenance, and repair expenses, and shall fix and determine the amounts to be set apart and applied to the payment of the interest on and retirement of the revenue bonds. All income and revenues as collected shall be paid to the state treasurer for the account of the department as a separate trust fund to be segregated and set apart for the payment of the revenue bonds, or may be remitted to and held by a designated trustee in such manner and with such collateral as may be provided in the resolution authorizing the issuance of the bonds.