It is the policy of the National Highway Traffic Safety Administration to issue notice of the action taken on a petition for reconsideration within 90 days after the closing date for receipt of such petitions, unless it is found impracticable to take action within that time. In cases where it is so found and the delay beyond that period is expected to be substantial, notice of that fact, and the date by which it is expected that action will be taken, will be published in the Federal Register.