49 CFR §211.53

Applications for approval of discontinuance or material modification of a signal system authorized by part 235 or waiver of a requirement of part 236 of this chapter must be submitted in accordance with § 211.7, handled in accordance with procedures set forth in part 235 or 236, respectively, and decided not later than 9 months after receipt. When a decision is issued, the applicant and other interested parties are notified or a notice is published in the Federal Register.