No person shall move or operate any tractor, heavy machine, structure or road roller across any curb, gutter, bridge, culvert, sidewalk, crosswalk or crossing in any unpaved street within the city without first having protected such curb, gutter, bridge, culvert, sidewalk, crosswalk or crossing with heavy plank sufficient in strength to warrant against breaking or damaging of such curb, gutter, bridge, culvert, sidewalk, crosswalk or crossing and without first having obtained permission from the office of the public works director.
(1964 Code, § 19-6)