53 Pa. Stat. § 22766
In the preparation of such plan the commission shall make careful and comprehensive surveys and studies of present conditions and probable future growth of the city and with due regard to its relation to neighboring territory. The plan shall be made with the general purpose of guiding and accomplishing a coordinated, adjusted, and harmonious development of the city and its environs which will, in accordance with present and future needs, best promote health, safety, morals, order, convenience, prosperity, and general welfare as well as efficiency and economy in the process of development, including, among other things, adequate provision for traffic, the promotion of safety from fire and other dangers, adequate provision for light and air, the promotion of the distribution of population, the promotion of good civic design and arrangement, wise and efficient expenditure of public funds and the adequate provision of public utilities and other public requirements.
53 P.S. § 22766