36 Pa. Stat. § 670-209
When the terminal point of one or more State highway routes is described as being at the boundary line of a county, township, municipality or adjoining state and the highway continues beyond such point, the secretary shall have authority to relocate such State highway route or routes, without limitation on account of such terminal point, except that the new point of crossing of such line shall be properly referenced and shown on the plan by which the relocation is made. When the terminal point of a State highway route is described as being on another highway, the secretary shall have authority to relocate such highway route, without limitation on account of such terminal point, except that the new terminal point shall be on such other highway. When two separate State Highway routes with one common terminal point form a continuous highway, the secretary shall have authority to relocate such State highway routes, without limitation on account of such terminal point, except that both the old and the new terminal points shall be shown on the plan by which the relocation is made.
36 P.S. § 670-209