49 CFR §211.31

1. (a)The Administrator may grant or deny, in whole or in part, any petition for reconsideration of a final rule without further proceedings. Each petition shall be decided not later than 4 months after its receipt by the Docket Clerk. In the event he determines to reconsider a rule, the Administrator may amend the rule or initiate a new rulemaking proceeding. An appropriate notice is published in the Federal Register.
2. (b)Whenever the Administrator determines that a petition should be granted or denied, a notice of the grant or denial of a petition for reconsideration is sent to the petitioner. When a petition is granted, a notice is published in the Federal Register.
3. (c)The Administrator may consolidate petitions relating to the same rule.