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SUMMARY: On July 27, 2009, NHTSA published a final rule that amended the Federal motor vehicle safety standard for air brake systems by requiring substantial improvements in stopping distance performance on new truck tractors. This final rule responds to petitions for reconsideration of a July 27, 2011 final rule that slightly relaxed the stopping distance requirement for typical loaded tractors tested from an initial speed of 20 mph. NHTSA is granting the request to remove the stopping distance requirements for speeds of 20 mph and 25 mph and denying the request to relax the stopping distance requirements for speeds between 30 mph and 55 mph.