In any district on any corner lot, no fence, sign (other than a post(s) or pylon(s) having a diameter of eight inches or less) or other structure, planting or other obstruction to vision in excess of 30 inches up to a height of eight feet above the existing street grade shall be erected or maintained within a triangular area formed by a line connecting points on the two street lines located a distance as specified in Section 15-7 of the Revised General Ordinances of the Township of Warren.