74 Pa. Stat. § 120.17
Exclusive jurisdiction in and over the aforesaid lands is hereby ceded to the United States of America by the Commonwealth of Pennsylvania, for the erection of forts, magazines, arsenals, dock yards and other needful buildings, with the exception of roads abutting on said lands to be used by the United States for military and other public purposes, which are not already under the jurisdiction of the United States, and: Provided further, That the above cession is hereby made contingent upon the United States of America making provision acceptable to the Department of Highways of the Commonwealth of Pennsylvania for a substitute road outside the limits of the said depot to replace that portion of State Highway Route No. 340 within the said depot, which has been rendered inaccessible to the traveling public.
74 P.S. § 120.17