49 C.F.R. § 211.75 – Evidence.

(a) The Federal Rules of Evidence for United States Courts and Magistrates shall be employed as general guidelines for the introduction of evidence in proceedings under this subpart. However, except as provided in paragraph (b) of this section, all relevant and probative evidence offered by a party shall be received in evidence.
(b) The presiding officer may deny the admission of evidence which is determined to be—
1. (1) Unduly repetitive; or
2. (2) So extensive and lacking in relevance or probative effect that its admission would impair the prompt, orderly, and fair resolution of the proceeding.