No structure, other than a permitted directional or information sign, boundary walls or fences, greater than six (6) feet in height, shall be erected within thirty (30) feet of any public roadway right-of-way line. No structure exceeding thirty-six (36) inches in height may be erected within the triangular area bound by the property lines and a line connecting the two (2) points on the property lines thirty (30) feet from the intersection of the property lines. Likewise, in the case of corner lots, no plant material exceeding a height of thirty-six (36) inches above the elevation of the street pavement, may be planted or maintained, within the triangular area bound by the property lines and a line connecting the two (2) points on the property lines thirty (30) feet from the intersection of the property lines.