NHTSA Proposes Tougher Brake Standards
Oliver B.Patton
Washington Editor
The National Highway Traffic Safety Administration is proposing to toughen tractor brake standards by requiring shorter stopping distances.
The agency is targeting a 20 percent to 30 percent improvement in stopping distance for both service and emergency brakes, and said it has tentatively concluded that this can be achieved with existing technology – specifically, with larger drum brakes.
In keeping with its standard practice, the agency does not intend to specify how to make a tractor stop more quickly.
"The agency will not mandate a technology, it will mandate a performance," said Robert Braswell, technical director of the Technology and Maintenance Council of the American Trucking Associations.
But the idea of setting a performance range, rather than a specific distance, is new – and welcome, according to Jim Tipka, vice president of engineering at ATA. Historically, the federal standard has been a fixed number, depending on speed and type of vehicle. For example, the current rule requires a loaded tractor moving at 60 mph to stop within 355 feet.
"The range makes sense," Tipka said.
NHTSA tested a variety of technologies, including standard S-cam drum brakes, larger capacity drum brakes and air disc brakes. It found that disc brakes at all wheels, or discs on some axles and drums on others, performed best by a significant margin.
Disc brakes on all wheels improved stopping distance by well over 30 percent, and the hybrid approach met the 20 percent to 30 percent target, for example. But larger drum brakes also can stop tractors within the 20 percent to 30 percent range, the agency found.
Tipka characterized the proposal as a conservative approach to improving braking performance. "The equipment is available," he said.
Relatively few trucks are equipped with the larger drum brakes right now. Citing a 2004 report by the Heavy Duty Brake Manufacturers Council, the agency said that approximately 10 percent of new tractors have the larger S-cam drum brakes (16.5-inch by 5-inch and 16.5-inch by 6-inch) on their steer axles. Just 3 percent of tractors are equipped with wider, extended-life brakes (16.5-inch by 8-inch and 16.5-inch by 8.625-inch).
But the transition to large drum brakes would be easier than a transition to disc brakes. The industry would have significant difficulty making that move, for two sets of reasons. Braswell noted that disc brakes have problems with durability, and both Braswell and Tipka stressed that the key issue in truck braking is compatibility between tractor and trailer.
"If the tractor and trailer have the same (brake) system and are married, it's OK," Braswell said. "But it becomes a problem if they are mixed." Given current operating practices in the industry, it is impossible to know which tractor will be pulling which trailer at any given moment.
Tipka said the industry has been waiting for this proposal for a couple of years, and it is not a surprise. "We don't have any concerns about what we've seen so far," he said. "Right now it's pretty much what we expected." He said ATA will confer with its members before preparing comments.
The proposal was published in the Dec. 15 Federal Register (http://dms.dot.gov). Go to docket number 21462. NHTSA is asking for comments by April 14. Tipka was unwilling to guess when the final rule might be published. In any event, the agency said it will grant a two-year lead time before the requirement is effective.
Washington Report continued...
