At or before the issuance of any bonds, the State Highway Commission shall:
(1) By resolution provide for a sinking fund for the payment of the principal of the bonds and the interest thereon and for the payment of the charges of banks or trust companies for making payment of the principal and interest; and
(2) Set aside and pledge a sufficient amount of the gross revenues of the bridge or ferry to be paid by the commission into the sinking fund at intervals to be determined by the resolution of the commission prior to the issuance of the bonds for: The interest upon such bonds as the interest shall fall due;
(3) The necessary fiscal agency charges for paying principal and interest;
(4) The payment of the bonds as they fall due, or if all bonds mature at one (1) time, the proper maintenance of a sinking fund sufficient for the payment thereof at that time; and
(5) A margin for safety.