In the event that 34th Avenue remains a mapped street, all developments or enlargements on 34th Avenue shall provide a sidewalk widening of no less than 13 feet in width. No obstructions shall be permitted from the lowest level to the sky except for those permitted pursuant to Section 37-53 (Design Standards for Pedestrian Circulation Spaces), paragraph (f)(3). When one end of the sidewalk widening abuts an existing building, the special design treatment specified in Section 37-53, paragraph (f)(5), shall be required.