36 Pa. Stat. § 670-423
When any State highway shall be closed, it shall be the duty of the department to immediately designate or lay out a detour, on which it shall erect or cause to be created and maintained, while such detour is in use, legible signs at each public road intersection throughout its entire length, indicating the direction to the main highway. During the period when such detour is in use, it shall be the duty of the department to maintain such detour in safe and passable condition. It shall also be the duty of the department to remove all detour signs immediately upon the opening for traffic of the highway originally closed. The department shall, as soon as possible, repair the road designated as a detour, and place same in a condition at least equal to its condition when designated as a detour. Whenever necessary in the creation of a detour, the department may enter into agreement with the owners of private lands, covering the acquisition of right of way privileges over private property for the period when the main highway shall be closed to traffic. In case no agreement satisfactory to the parties can be reached, the department may proceed with the construction of the same, and either the department or the owner of the property occupied may petition the court for the appointment of viewers to ascertain the damages, if any, in the same manner as provided by Article III of this act.
36 P.S. § 670-423