36 Pa. Stat. § 670-401
The department shall construct or improve, and thereafter maintain and repair, at the cost and expense of the Commonwealth, the highways forming the plan or system of the State highways, in the several counties and townships. Such improvement and maintenance shall be made according to specifications to be prepared by the department, as regards the character, construction, and material to be used. The work of construction and maintenance of said State highways shall be done under the direction and supervision of the secretary. The secretary, in addition to the powers conferred upon him in this act, shall enjoy and possess, in the construction and maintenance of State highways, all the rights and powers conferred by existing laws on supervisors or commissioners in townships in the construction or maintenance of township roads.
36 P.S. § 670-401