36 Pa. Stat. § 670-206
The secretary shall have power, with the approval of the Governor, to establish the ultimate width and lines of any State highway for future construction before or after the construction, reconstruction, or improvement of the same, not, however, exceeding the maximum width fixed by law for public roads. The establishment of such ultimate width and lines for future construction shall be by a plan, showing the center line of said highway and the established ultimate width thereof for future construction, bearing the acknowledgment of the secretary. Such plan and acknowledgment shall be recorded in the office of the recorder of deeds of the proper county, in a separate book kept for such purpose, which shall be furnished to the recorder of deeds by the county commissioners at the expense of the county. All costs of the recording shall be paid by the county.
36 P.S. § 670-206