The lot requirements for planned unit development approval by the Commission may vary from requirements prevailing for the district as follows:
(a) Lot width and setback and yard requirements may be varied to accommodate a variety of structural patterns, clustering designs, and housing types.
(b) Lot area per dwelling unit requirements of the R-1 Single-family Detached District may be reduced by not more than twenty (20) percent.
(c) Lot areas and dwelling unit densities shall not provide for developments which exceed four (4) dwelling units per acre when applied to the gross area of district.
(d) Each property in the RPUD district shall abut common open space or similar areas, provided however, that any property not abutting such uses shall have well designed access to, and shall be no more than 500 feet from, such uses.