PA Planned Apartment Districts are designed to make special provision for low lot coverage, low-density apartment development in designated portions of residence districts in the City where apartment development is considered appropriate by virtue of such criteria as direct access to major highways, availability of public sewer and water facilities, adequacy of or provision for school, recreation and other community facilities, environmental amenity and safety and economic viability. In those portions of residence districts which have also been classified as PA Planned Apartment Districts, the following regulations shall apply.