No fence, wall, hedge, or other structure or other obstruction above a height of thirty six (36) inches as measured above the curb level shall be erected, placed, maintained or continued in any zone within that triangular portion of a corner lot formed by measuring ten (10) feet from the intersection of the rights of way line or two (2) streets or fifty (50) feet of the right of way line of a street intersection with a railroad right of way line and joining these points with a straight line; except in the CBD zone which shall be controlled by the minimum setback requirements. No type of tree or planting or other obstruction shall be planted, placed, maintained or continued in such a manner which would obstruct the vision clearance at corners and railroad crossings.