To permit in District "R-1" to "R-3" inclusive, semi-public parking areas for occupants of apartment houses, multiple dwellings, hotels, apartment hotels, fraternity or sorority houses, lodging houses, member of clubs, and visitors to or patrons of hospitals, institutions, or places of public assembly, provided that such parking areas be improved as required in Sections 400.220 — 400.260, and provided that such parking areas are located not more than three hundred (300) feet therefrom.