The rule was originally scheduled to be published two years ago. The original notice of proposed rulemaking was published in December 2005. The rule is waiting for clearance by the White House Office of Management and Budget.
This rulemaking would reduce stopping distance requirements for truck tractors equipped with air brake systems. Advances in heavy vehicle braking systems show that improved stopping performance is attainable for these vehicles, says NHTSA. Such improvements would reduce the stopping distance disparity with light vehicles, and would result in fewer deaths and injuries and reduce property damage due to fewer crashes between truck tractors and light vehicles.
It is widely expected that the new rules will result in disc brakes becoming the typical spec on steer axles, and either disc brakes or wider drum brakes on the drive axles.