On a corner lot in any residential district, nothing shall be erected, placed, planted or allowed to grow in such a manner as materially to impede vision between a height of 2.5 and 10 feet above the centerline grades of the intersecting streets in the area bounded by the street lines of such corner lots and a line joining points along the street lines 20 feet from the point of the intersection. [Ord. 378 § 2 (Exh. 1), 1999.]