49 C.F.R. § 5.3 – General.

(a) This subpart governs all DOT employees and contractors involved with all phases of rulemaking at DOT.
(b) Unless otherwise required by statute, this subpart applies to all DOT regulations, which shall include all rules of general applicability promulgated by any components of the Department that affect the rights or obligations of persons outside the Department, including substantive rules, rules of interpretation, and rules prescribing agency procedures and practice requirements applicable to outside parties.
(c) Except as provided in paragraph (d) of this section, this subpart applies to all regulatory actions intended to lead to the promulgation of a rule and any other generally applicable agency directives, circulars, or pronouncements concerning matters within the jurisdiction of an OA or component of OST that are intended to have the force or effect of law or that are required by statute to satisfy the rulemaking procedures specified in 5 U.S.C. 553 or 5 U.S.C. 556.
(d) This subpart does not apply to:
1. (1) Any rulemaking in which a notice of proposed rulemaking was issued before December 20, 2018, and which was still in progress on that date;
2. (2) Regulations issued with respect to a military or foreign affairs function of the United States;
3. (3) Rules addressed solely to internal agency management or personnel matters;
4. (4) Regulations related to Federal Government procurement; or
5. (5) Guidance documents, which are not intended to, and do not in fact, have the force or effect of law for parties outside of the Department, and which are governed by part 5, subpart C of this chapter.