SUMMARY: This document amends the Federal motor vehicle safety standard on air brake systems to improve the stopping distance performance of truck tractors. The rule requires the vast majority of new heavy truck tractors to achieve a 30 percent reduction in stopping distance compared to currently required levels. For these heavy truck tractors (approximately 99 percent of the fleet)@ the amended standard requires those vehicles to stop in not more than 250 feet when loaded to their gross vehicle weight rating (GVWR) and tested at a speed of 60 miles per hour (mph). For a small number of very heavy severe service tractors@ the stopping distance requirement will be 310 feet under these same conditions. In addition@ this final rule requires that all heavy truck tractors must stop within 235 feet when loaded to their ????lightly loaded vehicle weight'' (LLVW). The purpose of these amendments is to reduce the number of fatalities and injuries associated with crashes involving tractor-trailer combinations and other vehicles. In addition@ we anticipate that this rule will prevent a substantial amount of property damage through averting or lessening the severity of crashes involving these vehicles. Once all subject heavy truck tractors on the road are equipped with enhanced braking systems@ we estimate that annually@ approximately 227 lives will be saved and 300 serious injuries will be prevented. In addition@ this final rule is expected to prevent over $169 million in property damage annually@ an amount which alone is expected to exceed the total cost of the rule. There are a number of simple and effective manufacturing solutions that vehicle manufacturers can use to meet the requirements of this final rule. These solutions include installation of enhanced drum brakes@ air disc brakes@ or hybrid disc/drum systems. We note that currently a number of vehicles in the commercial fleet already utilize these improved braking systems and already realize performance that would meet the requirements of the amended standard.