Section 91. Every company shall, in a manner satisfactory to the department, erect and maintain guards or railings upon every bridge, or draw of a bridge, crossed by its tracks, to prevent its cars from running off. If, for sixty days after service on it of an order of the department relative to such guards or railings, it fails to comply therewith, it shall, for each month of such failure subsequent to said sixty days, forfeit two hundred dollars, to the use of the city or town.