36 Pa. Stat. § 670-762
Whenever it shall appear to the secretary that any part or portion of a State highway route or routes in a city of the first class which constitutes or constitute a part of the approaches to an interstate bridge are dangerous or inconvenient to the traveling public in their then location, either by reason of width, grade, lines, curves or other conditions, or that the expense to the Commonwealth in the construction or maintenance thereof could be materially lessened by a change of location, the secretary may, with the consent of the Governor and of the city expressed by ordinance or resolution, change the location of such State highway route, including the terminal points thereof, to pass over existing streets or new streets laid out and opened by the city in such manner, as in his discretion, may seem best in order to correct such danger or inconvenience or lessen the cost to the Commonwealth. A plan showing the new location, approved by the Governor and the mayor of the city, shall be recorded in the office of the recorder of deeds in the county in which such city shall be located.
After the relocation has been opened to traffic, the secretary by notice to the local authorities, may abandon, as a State highway route, all or any part of the section of highway between the termini of the relocation.
36 P.S. § 670-762