In the discretion of the governing body of any such county or counties issuing bonds under the provisions of this article, each or any issue of such bonds may be secured by a trust indenture by and between such county or counties and a corporate trustee, which may be any trust company or bank having the powers of a trust company within or outside of the state. Said trust indenture may, in the discretion of the governing body, convey or mortgage the revenues, the bridge, or any part thereof.

Either the resolution providing for the issuance of bridge revenue bonds or such trust indenture may contain such provisions for protecting and enforcing the rights and remedies of the bondholders as may be reasonable and proper and not in violation of law, including covenants setting forth the duties of such county or counties and the governing body thereof in relation to the construction, maintenance, operation, repair, and insurance of the bridges, and the custody, safeguarding, and application of all moneys; and it may also provide that the bridge or bridges shall be constructed and paid for under the supervision and approval of consulting engineers employed or designated by the governing body of such county or counties and satisfactory to the original purchasers of the bonds issued therefor, and may also require that the security given by contractors and by any depository of the proceeds of the bonds or revenues of the bridges or other moneys pertaining thereto be satisfactory to such purchasers. It shall be lawful for any bank or trust company incorporated under the laws of this state to act as such depository and to furnish such indemnifying bonds or to pledge such securities as may be required by the governing body of such county or counties. Such indenture may set forth the rights and remedies of the bondholders and of the trustee, and may restrict the individual right of action of bondholders as is customary in trust indentures securing bonds and debentures of corporations. Except as in this article otherwise provided, the governing body of such county or counties may provide, by resolution or by such trust indenture, for the payment of the proceeds of the sale of the bonds and the revenues of the bridges to such officer, board, or depository as it may determine for the custody thereof, and for the method of disbursement thereof with such safeguards and restrictions as it may determine. All expenses incurred in carrying out such trust indenture may be treated as a part of the cost of maintenance, operation, and repair of the bridge or bridges affected by such indenture.