15 U.S.C. § 1006

(a) The use of the San Francisco-Oakland Bay Bridge free of toll, provided for in section 1005 of this title , shall be granted upon the presentation and surrender at the toll lanes of an authorization certifying that the traffic or person in question is entitled to such right. Such authorization shall be issued and signed by any officer or official designated for such purpose in accordance with regulations which shall be prescribed by the Secretary of the Department having control of the personnel exempted by section 1005 of this title . The names and signatures of officers so designated shall be furnished to the California Toll Bridge Authority and thereafter authorizations signed by them shall be accepted by such authority as prima facie evidence of the facts stated therein. (b) Notwithstanding the provisions of subsection (a), such right to use the San Francisco-Oakland Bay Bridge free of toll may be established by any other device or means which may be acceptable to the California Toll Bridge Authority; and the Secretary of the appropriate Department and the California Toll Bridge Authority may enter into any appropriate agreements to secure the effective, convenient, and just exercise of such right.