The commissioner shall maintain each bridge on any highway maintained by him, except as otherwise specifically provided by law. Such maintenance shall include the preservation, restoration or replacement of any or all parts of the structure as may be necessary to permit it to be used with safety by the traveling public, subject to such restrictions as may be provided by law, and the use of electric current and the servicing and repair necessary to keep in operation any system of lighting installed on any bridge in accordance with the provisions of subsection (b) of § 13a-110.