It shall be the duty of every railroad and street railroad to so sprinkle with water, or treat with oil, or otherwise treat that part of the surface of each street occupied or used by its tracks between the rails and between the tracks and a strip two (2) feet in width on each side thereof, that dust will remain settled on said portions of such street when any train, car or rolling equipment is operated on such tracks; provided, however, that said requirement shall not apply when such streets are paved.