Where district boundaries are indicated as approximately coinciding with the center lines of roads, creeks, streams or railroad rights-of-way, such center lines shall be construed to be such boundaries. Where district boundaries are so indicated that they are approximately parallel to center lines of roads, creeks, streams or railroad rights-of-way, such district boundaries shall be construed as being parallel thereto and at such distance therefrom as indicated by scale or dimension on the Zoning District Map.