The department shall mark all overpasses on all state and state aid highways, and on all other highways for which state funds are provided by law, with the height of the clearance of such overpass and such markings shall be maintained so as to be clearly visible for a distance of 200 feet on the highway. The same requirements shall apply to highway bridges when the vertical underclearance is limited by the portal, bracing or other structural members. This section shall apply only when the vertical clearance is less than 14 feet 6 inches. The clearance indicated is to be the normal summer clearance. Such overpasses not indicated herein shall be marked by the municipalities in which the same shall be found and in accordance with the standards for marking set forth. [PL 1971, c. 593, §22 (AMD).]