Fences, hedges, walls, and screen plantings not exceeding eight (8) feet in height may occupy any interior side yard and/or rear yard, and in the front yard and/or exterior side yard area situated behind the building setback lines. Except that in all zoning districts, there shall be a clear vision triangle on either side of a driveway intersecting with a public street right-of-way. The triangle is an area bounded by the street property line and the driveway and a line connecting them ten (10) feet from their intersection. When either the street or driveway is curvilinear, measurement shall be taken from the point of intersection using a ninety (90) degree angle which most closely aligns to both the driveway and street line. Within both triangles on either side of the driveway the area between three (3) and eight (8) feet in height as measured from the top of the curb adjacent to the driveway shall be clear of vision obstructions. Trees may penetrate the clear area so long as there are not branches lower than eight (8) feet and the trunk, or trunks if there are multiple trees, do not exceed a combined width of four (4) feet. If no curb exists, the City Engineer shall establish curb grade.