4. Stretch limousine compliance with Federal safety standards (a) In general Chapter 301 of subtitle VI of title 49, United States Code, is amended by inserting after section 30128 the following new section: 30129. Stretch limousine compliance with Federal safety standards (a) Guidelines, best practices, and recommendations Not later than 2 years after the date of enactment of this section, and not less than every 4 years thereafter, the Secretary shall develop and issue guidelines, best practices, and recommendations to assist a stretch limousine alterer to develop and administer the vehicle modifier plan required under subsection (c). (b) Process and analysis (1) Notice required Not later than 2 years after the date of enactment of this section, and as necessary thereafter, the Secretary shall publish a notice in the Federal Register that describes the process and analysis used for approving or denying a vehicle modifier plan submitted by a stretch limousine alterer. (2) Elements The notice required under paragraph (1) shall include— (A) a description of the safety elements described in subsection (c) in a vehicle modifier plan