WASHINGTON, (Nov. 22, 2004) — All the talk about the U.S. government requiring shorter stopping distances for big rigs will remain talk for quite a while, according to Jim Britel, a research engineer at the National Highway Transportation Safety Administration, which is pondering new requirements.

Heavy Duty Trucking recently reported that Britel says NHTSA rule makers are taking longer than anyone anticipated to come up with a proposed revision.

The final rule would have to provide lead time for truck builders and brake makers to prepare for changes, which could add another year or more to an effective date. So the likely date would push past Jan. 1, 2007.

January of ’07 is also the time that stricter diesel exhaust-emissions regulations take effect, and brake people thought that the government might consider that a convenient time for new brake rules. But Britel — who emphasizes that he’s an engineer, not a rule writer — said that NHTSA people realize that truck engineers will be preoccupied with engines and have little time for brakes. So it’s likely that the effective date will be many months later.

The regulation that NHTSA is working on is Federal Motor Vehicle Safety Standard 121, which governs how truck air brakes must work. Among anticipated changes is a 30 per cent reduction in stopping distances for heavy trucks. For example, a tractor-trailer weighing 56,600 pounds and going 60 mph must now stop within 355 feet. Thirty percent less is 248.5 feet, and engineers would likely shoot for a 10 per cent margin of error, which would be as quick as 224 feet — close to what’s required for cars.

High-performance drum brakes might meet that requirement, but discs on a tractor’s steer axle — where much stopping work is done under emergency conditions — would be better. And discs would probably be necessary if NHTSA establishes new limits for stopping from 70 or 75 mph, which are not now required.

Two earlier revisions to “121,” in the 1970s and ’90s, mandated anti-lock braking systems for air-braked trucks. ABS of the ’70s was a fiasco, but modern versions generally work well. Industry observers hope the next rewrite of 121 will make both safety and business sense.

— from Heavy Duty Trucking