49 CFR § 386.37 - Discovery.
(a) Parties may obtain discovery by one or more of the following methods: Depositions upon oral examination or written questions; written interrogatories; request for production of documents or other evidence for inspection and other purposes; physical and mental examinations; and requests for admission.
(b) Discovery may not commence until the matter is pending before the Assistant Administrator or referred to the Office of Hearings.
(c) Except as otherwise provided in these rules, in the Administrative Procedure Act, 5 U.S.C. 551 et seq., or by the Assistant Administrator or Administrative Law Judge, in the absence of specific Agency provisions or regulations, the Federal Rules of Civil Procedure may serve as guidance in administrative adjudications.