36 Pa. Stat. § 668.15
The Commission is hereby authorized to fix, and to revise from time to time, tolls for the use of the turnpike and the different parts or sections thereof, and to charge and collect the same, and to contract with any person, partnership, association or corporation desiring the use of any part thereof, including the right-of-way adjoining the paved portion, for placing thereon telephone, telegraph, electric light or power lines, gas stations, garages, stores, hotels, restaurants, and advertising signs, or for any other purpose, except for tracks for railroad or railway use, and to fix the terms, conditions, rents and rates of charges for such use. Such tolls shall be so fixed and adjusted as to provide a fund at least sufficient with other revenues of the turnpike, if any, to pay (a) the cost of maintaining, repairing and operating the turnpike, and (b) the bonds, notes or other obligations and the interest thereon, and all sinking fund requirements, and other requirements provided by the resolution authorizing the issuance of the bonds, notes or other obligations, or by the trust indenture, as the same shall become due. Such tolls shall not be subject to supervision or regulation by any other State commission, board, bureau or agency. The tolls and all other revenues derived from the turnpike, except such part thereof as may be required to pay the cost of maintaining, repairing and operating the turnpike and to provide such reserves therefor as may be provided for in the resolution authorizing the issuance of the bonds, notes or other obligations, or in the trust indenture, shall be set aside, at such regular intervals as may be provided in such resolution or such trust indenture, in a sinking fund, which is hereby pledged to and charged with the payment of (1) the interest upon such bonds, notes or other obligations, as such interest shall fall due, (2) the principal of the bonds, notes or other obligations, as the same shall fall due, (3) the necessary fiscal agency charges for paying principal and interest, and (4) any premium upon bonds retired by call or purchase, as herein provided. The use and disposition of such sinking fund shall be subject to such regulations as may be provided in the resolution authorizing the issuance of bonds, notes or other obligations, or in the trust indenture, but, except as may otherwise be provided in such resolution or trust indenture, such sinking fund shall be a fund for the benefit of all bonds, notes or other obligations issued hereunder, without distinction or priority of one over another. Subject to the provisions of the resolutions authorizing the issuance of bonds, notes or other obligations, or of the trust indenture, any moneys in such sinking fund in excess of an amount equal to one year's interest on all bonds, notes or other obligations then outstanding may be applied to the purchase or redemption of bonds, notes or other obligations. All bonds, notes or other obligations so purchased or redeemed shall forthwith be cancelled and shall not again be issued.
36 P.S. § 668.15