49 C.F.R. § 106.120

(a) Appeal of a final rule or withdrawal of a notice of proposed rulemaking. If you appeal PHMSA's issuance of a final rule or PHMSA's withdrawal of a proposed rulemaking, your appeal document must reach us no later than 30 days after the date PHMSA published the regulation or the withdrawal notice in the Federal Register. After that time, PHMSA will consider your appeal to be a petition for rulemaking under § 106.100.

(b) Appeal of a decision. If you appeal PHMSA's decision on a petition for rulemaking, your appeal document must reach us no later than 30 days from the date PHMSA served you with written notice of PHMSA's decision.