49 CFR 511.36: Motions to compel discovery.

If a party fails to respond to discovery, in whole or in part, the party seeking discovery may move within twenty (20) days for an order compelling an answer, or compelling inspection or production of documents, or otherwise compelling discovery. For purposes of this subsection, an evasive or incomplete response is to be treated as a failure to respond. If the motion is granted, the Presiding Officer shall issue an order compelling discovery. If the motion is denied in whole or in part, the Presiding Officer may make such protective order as he or she would have been empowered to make on a motion pursuant to § 511.31(d). When making oral examinations, the discovering party shall continue the examination to the extent possible with respect to other areas of inquiry before moving to compel discovery.