Va. Code § 33.2-1720
The tolls and all other revenues derived from the project for which a single issue of bonds is issued, except such part thereof as may be required to pay the cost of maintaining, repairing, and operating such project and to provide such reserves therefor as may be provided for in the resolution authorizing the issuance of such bonds 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 that is hereby pledged to and charged with the payment of (i) the interest upon such bonds as such interest shall fall due, (ii) the principal of the bonds as the same shall fall due, (iii) the necessary charges of paying agents for paying principal and interest, and (iv) any premium upon bonds retired by call or purchase as provided in this section.
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 the bonds 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 all such bonds without distinction or priority of one over another. Subject to the provisions of the resolution authorizing the issuance of the bonds 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 then outstanding may be applied to the purchase or redemption of bonds. All bonds so purchased or redeemed shall forthwith be cancelled and shall not again be issued.
Va. Code § 33.2-1720