Fences, walls, hedges and other plant materials shall not be located at street corners so as to interfere with vision clearance across the corner lots. The height of such objects is restricted to three feet within a triangular area formed by the intersecting street lines and a line joining points on the street lines and equidistant from the point of intersection. This distance shall be 30 feet from the corner. In addition, no fence, wall, hedge or other plant material shall be placed or allowed to grow in such a manner as to impede vision from driveways on the owner's lot or adjacent lots.