; or (B) the alternative compliance approach demonstrated by the waiver. (3) Timing (A) Notifications Not later than 60 days after receiving a request under paragraph (1), the Secretary shall provide written notification to the petitioner that describes whether the relevant terms of the waiver will be incorporated into regulation as an alternative compliance approach. (B) Notice of proposed rulemaking If the relevant terms of the waiver will be incorporated into regulation as an alternative compliance approach, not later than 270 days after the date of the written notification under subparagraph (A), the Secretary shall issue a notice of proposed rulemaking that incorporates the waiver with the least burdensome terms necessary to ensure flexibility among various operations while meeting the regulatory safety objective. (C) Final rule Not later than 2 years after the date the notice of proposed rulemaking is issued under subparagraph (B), the Secretary shall issue the final rule under this subsection. (i) Nonapplicability This section does not apply to any petition that, if approved, would result in a reduction in the number of route miles that are required under section 20157 to have operations governed by a positive train control system. (j) Rules of construction (1) In general Nothing in this section may be construed— (A) to limit the authority of the Secretary— (i) to grant a waiver under other law, including the authority to grant any waiver that is not a regulatory improvement waiver; or (ii) to promulgate, rescind, or revise such regulations as are necessary to carry out the functions of the Secretary under this subtitle; (B) to prohibit a person from requesting a waiver under other law, including any waiver that is not a regulatory improvement waiver