36 Pa. Stat. § 670-422
Except in the case of emergencies wherein the safety of the public would be endangered, no State highway shall be closed to vehicular traffic, except upon order of the department nor for a longer period than is necessary for the purpose for which such order is issued. No public road or highway shall be closed to vehicular traffic when the same has been designated as a detour by the department, unless the written consent of the department has first been obtained, or unless the authorities having jurisdiction over said road or highway shall, by resolution duly recorded on their minutes, declare such closing necessary for the protection of the public safety.
When any borough, town or city street, which forms a part or section of a State highway, is closed to vehicular traffic, the borough, town or city shall at once notify the department of the creation of a detour, as hereinafter provided, and when such detour is removed, the department shall also be notified at once of the removal.
36 P.S. § 670-422