California Code, Streets and Highways Code - SHC § 31152

The authority may provide in the proceedings authorizing the issuance of bonds for the setting up of one or more reserve funds out of the proceeds of the bonds or out of the tolls and other revenues not needed for the payment of interest on the bonds and the principal of the bonds as they currently mature, and for the preservation and continuance thereof in a manner to be provided therein, and may also require the immediate application of all surplus money in any such toll revenue fund to the retirement, by call or purchase, of the bonds prior to maturity in such manner and upon such terms and the payment of such premiums as the authority deems advisable.