California Code, Public Utilities Code - PUC § 29142

(a) Revenues derived from the transactions and use taxes, not to exceed an aggregate principal amount of one hundred fifty million dollars ($150,000,000), plus the costs payable by the district to the State Board of Equalization for preparatory costs and for its services in connection with such taxes and plus the costs of issuance of, and interest payments on, bonds or notes secured by such revenues, shall be used for the planning, acquiring, and constructing of the district's approximately 75-mile system, including the San Francisco-Oakland Rapid Transit Tube and any and all works, structures, property, rolling stock, or other facilities of any kind which the district is authorized to acquire, construct, or complete.

(b) Revenues in excess of the amount specified in subdivision (a) shall be used for purposes specified in Section 29142.2, operational purposes, the liquidation of operational deficits, and the payment of principal and interest on negotiable bonds issued pursuant to subdivision (c).

(c) To finance the operation of its rapid transit system during the 1974-75 fiscal year, the district may issue negotiable bonds in an amount not to exceed sixteen million dollars ($16,000,000) in anticipation of the revenues specified in subdivision (b).  However, upon a determination by the board that the issuance of sixteen million dollars ($16,000,000) in negotiable bonds, together with other funds available to the district, provide insufficient funds for the operation of the district during the 1975-76 fiscal year, the district may issue additional negotiable bonds in an amount not exceeding eight million dollars ($8,000,000).  The district may also issue additional negotiable bonds in an amount not exceeding one million three hundred thousand dollars ($1,300,000) if the board determines that otherwise insufficient funds are available to the district for its operation during the 1976-77 fiscal year.  The district shall pay the principal and interest on such bonds only from such revenues.  Interest on such bonds may be funded, and paid from the proceeds of such bonds, for period of not to exceed two years from the date of such bonds.  The board, by resolution shall determine the form, denomination, maturities, interest rates, and all other terms and conditions relative to the issuance of such negotiable bonds.