36 Pa. Stat. § 655.3
The Pennsylvania Parkway Commission hereinafter created is hereby authorized and empowered to construct, operate and maintain the said parkway in accordance with the survey made by the Department of Highways, together with connecting tunnels and bridges, and to issue parkway revenue bonds of the Commonwealth, payable solely from tolls, to pay the cost of such construction.
Parkway revenue bonds issued under the provisions of this act shall not be deemed to be a debt of the Commonwealth or a pledge of the faith and credit of the Commonwealth, but such bonds shall be payable exclusively from the fund herein provided therefor from tolls. All such bonds shall contain a statement on their face that the Commonwealth is not obligated to pay the same or the interest thereon except from tolls and that the faith and credit of the Commonwealth is not pledged to the payment of the principal or interest of such bonds. The issuance of parkway revenue bonds under the provisions of this act shall not directly or indirectly or contingently obligate the Commonwealth to levy or to pledge any form of taxation whatever therefor or to make any appropriation for their payment.
36 P.S. § 655.3