Section 9A. The department, after a public hearing, may order the discontinuance of flashing lights on any billboard, sign or other advertising device, which in its opinion is so situated as to hinder the proper operation of a motor vehicle by distracting the operator's attention. Whoever fails to comply with said order shall be punished by a fine of not more than five hundred dollars or by imprisonment for not more than thirty days, or both. The provisions of this section shall not be construed so as to prohibit the display of time, weather or other such information. Nothing in this section shall be construed to restrict the powers granted to the outdoor advertising board and to the cities and towns under the provisions of section twenty-nine of chapter ninety-three.