The secretary may, upon compliance with the foregoing sections of this article, enter into a contract with any person, firm, or corporation, or the authorities of any city, borough or incorporated town, or the commissioners of any county, or the supervisors or commissioners of any township, to repair and maintain any State highway, or any portion thereof, including the construction or reconstruction or bridges thereon. The secretary may also contract with any person, firm or corporation for engineering services to lay out, design, and estimate the cost of constructing, altering or repairing highways and bridges.
36 P.S. § 670-408