16 Pa. Stat. § 8704
When a road or highway runs along the edge of a precipice, along which it may be necessary to erect guards or barriers for the proper protection of the traveling public, and the erecting of such guards or barriers requires more expense than it is reasonable the township should bear, the court having jurisdiction shall, on the representation of the supervisors or on the petition of any of the inhabitants of such township, order a view, in the manner provided for in the case of roads; and if on the report of viewers, it shall appear to the court, grand jury and commissioners of the county, that such guards or barriers are necessary and would be too expensive for such township, the same shall be erected and maintained as county bridges are now erected; and that the provisions of this act shall apply to roads already opened as well as those hereafter opened.
16 P.S. § 8704