49 CFR §7.21

1. (a)Except as otherwise provided in paragraph (b) of this section, this subpart applies to reasonably described records that are made available in response to written requests under FOIA.
2. (b)This subpart does not apply to:
   1. (1)Records published in the Federal Register.
   2. (2)Records published and offered for sale.
   3. (3)Records (other than frequently requested records) made available in a reading room.
   4. (4)Records or information compiled for law enforcement purposes and covered by the disclosure exemption described in § 7.23(c)(7)(A) if—
      1. (i)The investigation or proceeding involves a possible violation of criminal law; and
      2. (ii)There is reason to believe that—
         1. (A)The subject of the investigation or proceeding is not aware of its pendency; and
         2. (B)Disclosure of the existence of the records could reasonably be expected to interfere with enforcement proceedings.
   5. (5)Informant records maintained by any criminal law enforcement component of DOT under an informant's name or personal identifier, if requested by a third party according to the informant's name or personal identifier, unless the informant's status as an informant has been officially confirmed.