Va. Code Ann. § 15.2-948

The governing body of any locality may, within the limits permitted by the Constitution, designate any of its continuing sources of revenue, or portions thereof, as a stable and reliable source of revenue to pay its mass transit operating and debt service expenses to the extent that such designation is required by the United States as a prerequisite pursuant to Public Law 96-184 to the provision of funds for mass transit construction and debt service which benefits any such locality.