In any district except a CBD Central Business District, no fence, wall, shrubbery, sign or other obstruction to vision above a height of thirty-six (36) inches from the established street grade shall be permitted within the triangular area formed at the intersection of street right-of-way lines, by drawing a straight line between such right-of-way lines at a distance along each line of twenty-five (25) feet from their point of intersection. See Figure 15 in the Appendix.