a. Where forty (40) percent or more of the frontage on one side of a street between two (2) intersecting streets is developed with buildings that have observed (with a variation of five (5) feet or less) a front yard greater in depth than herein required, new buildings shall not be erected closer to the street than the front yard so established by the existing buildings.
b. Where forty (40) percent or more of the frontage on one side of a street between two (2) intersecting streets is developed with buildings that have not observed a front yard as described above, then
(1) Where a building is to be erected on a parcel of land that is within one hundred (100) feet of existing buildings on both sides, the minimum front yard shall be a line drawn between the two (2) closest front corners of the adjacent buildings on the two (2) sides, or
(2) Where a building is to be erected on a parcel of land that is within one hundred (100) feet of an existing building on one side only, such building may be erected as close to the street as the existing adjacent building.
(3) In determining such front yard depth, buildings located entirely on the rear one-half (1/2) of a lot shall not be counted.
c. Vision Clearance. On any corner lot on which a front or side yard is required, no wall, fence, sign, or other structure, or any plant growth shall be permitted or maintained higher than two (2) feet above the curb level within fifteen (15) feet of the intersection of the property lines.