On every corner lot, the triangle formed by the street lines of such lot and a line drawn between points on such street lines which are thirty feet (30') from the intersection thereof shall be clear of any structure or planting of such nature and dimension as to obstruct lateral vision; provided, that this requirement shall generally not apply to the trunk of a tree (but not branches or foliage) or a post, column or similar structure which is no greater than one foot (1') in cross section or diameter. Lateral vision shall be maintained between a height of thirty inches (30") and ten feet (10') above the average elevation of the existing surface of both streets measured along the center lines adjacent to the visibility triangle. (Ord. 96-21, 9-10-1996)