All streets, roads, highways, alleys, public ways and railroad rights-of-way, if not otherwise specifically designated, shall be deemed to be in the same district as the property immediately abutting upon the same. Where the center line of a street, road, highway, alley, public way or railroad right-of-way serves as a district boundary, the zoning of such areas, unless otherwise specifically designated, shall be deemed to be the same as that of the abutting property up to such center line.