No person operating a line of electric street railways shall require or permit the operation upon the lines of any electric car during the period beginning September 1st, and ending May 1st, of each year, unless each end of such car is provided with a solid vestibule which shall fully protect the motorman, conductor and passengers compelled to stand on the platform.

Whoever violates this Section shall be fined not more than three hundred dollars or imprisoned not more than six months or both.  Each day of violation shall constitute a separate offense.