When all bonds issued under the provisions of this act to finance any highway project or projects and the interest thereon shall have been paid or a sufficient amount for the payment of all such bonds and the interest thereon to the maturity thereof shall have been set aside in trust for the benefit of the bondholders, all such projects shall become part of the State highway system and shall thereafter be operated and maintained by the authority.
N.J.S. § 27:23-16