49 CFR § 663.43
Certification that Federal motor vehicle standards do not apply
November 18, 2020
(a) Except for rolling stock subject to paragraph (b) of this section, if a vehicle purchased under this part is not subject to the Federal Motor Vehicle Safety Standards issued by the National Highway Traffic Safety Administration in part 571 of this title, the recipient shall keep on file its certification that it received a statement to that effect from the manufacturer.
(b) This subpart shall not apply to rolling stock that is not a motor vehicle.