36 Pa. Stat. § 652m
The commission is hereby authorized to provide by resolution for the issuance of turnpike revenue refunding bonds of the Commonwealth for the purpose of refunding any turnpike revenue bonds issued under the provisions of this act and then outstanding, either by voluntary exchange with the holders of such outstanding bonds, or to provide funds to redeem and retire such outstanding bonds with accrued interest, and any premium payable thereon at maturity, or at any call date. The issuance of such turnpike revenue refunding bonds, the maturities and other details thereof, the rights of the holders thereof, and the duties of the Commonwealth and of the commission in respect to the same, shall be governed by the foregoing provisions of this act in so far as the same may be applicable: Provided, however, That no turnpike revenue refunding bonds shall be issued and delivered under the provisions of this section, unless the bonds to be refunded thereby shall mature within three months or unless the interest rate of the turnpike revenue refunding bonds shall be at least one-fourth of one per centum less than the interest rate borne by the turnpike revenue bonds to be refunded.
36 P.S. § 652m