The following regulations apply to planned residential developments:
(a) The lot area per family may be reduced, but such reduction shall not exceed thirty percent.
(b) Not less than ten percent of the total project area shall be devoted to open space and recreational facilities for the residents of the area being developed. The open space shall be disposed of as required in Section 1199.04. Every property subdivider under the planned unit development shall be designed to abut upon open space or similar areas. A clustering of dwellings is encouraged. In areas where townhouses are used, there shall be not more than five townhouse units in any contiguous group. A variety of building setbacks, colors and building materials for contiguous townhouse units is encouraged.
(c) The lot widths may be reduced by not more than twenty percent of the requirement of the Subdivision Regulations or this Zoning Code. The lots width may be varied due to the variety of structural designs, and it is recommended that setbacks be varied. If lot widths for residential lots are varied by the subdivider, he shall enter into an agreement with the City that the property owners within a planned unit development of this nature shall be assessed equally for any improvement which may be by assessment rather than on a front footage basis.