When the particular bonds issued for any bridge or bridges and the interest thereon shall have been paid, or a sufficient amount shall have been provided for their payment and shall continue to be held for that purpose, the municipality issuing such bonds shall cease to charge tolls for the use of such bridge or bridges; and thereafter such bridge or bridges shall be free unless tolls are required for maintaining, repairing, and operating such bridge or bridges due to the lack of funds from other sources than tolls. Such provisions shall not apply to common carriers, transportation companies, bus lines, and any one transporting passengers or freight for hire, but shall apply only to the use of highway portion of bridge by traveling public and, as respects any other use, the municipality may continue to fix and collect such tolls and charges as it may deem in the public interest.