In each quadrant of every street intersection there shall be designed a vision clearance triangle, bounded by the property lines and a line connecting them fifteen (15) feet from their intersection. Within this triangle, no object shall be allowed above the grade of two and one-half (2 1/2) feet above the streets if it obstructs the view across the triangle. This provision shall not apply to posts, wire fences, tree trunks, or other vertical supporting members not more than twelve (12) inches square in horizontal cross section; however, in situations where there are trees of large diameter, large numbers of trees, or a combination of these, this provision shall be construed to mean that a sufficient number of trees shall be removed so as to render a clear view across the vision triangle from one (1) street to another. The intent is to provide for public safety.