The National Highway Traffic Safety Administration – the arm of DOT that writes equipment regulations – wants three-axle tractors to be able to stop much faster in order to reduce accidents.

So far, the proposal is in the information gathering stage. NHTSA is asking for feedback from truckers, truck manufacturers and brake suppliers. Nobody seems to care much for the 30 percent reduction, which likely would require expensive air disc brakes, at least on front axles. And at 20 percent, I'm told it would take bigger S-cam front brakes as a minimum.

Doing the math, today's loaded air-braked rig with trailer must stop in 355 feet from 60 mph. A 20 percent reduction would drop this to 285 feet; 30 percent would take it to 250 feet. That's darn short – about three-quarters the length of a football field.

NHTSA wants to adopt the shorter stopping distance in 2008 or '09. This would sandwich another expensive equipment change in between EPA's exhaust emissions regulations, which begin next year and in 2010. These are already taxing the technical and financial resources of manufacturers. Engineering time and costs to accomplish major brake changes in the middle of all this would hurt all segments of the industry.

The American Trucking Associations says it's okay with a 20 percent stopping reduction, claiming the shorter stopping distance shouldn't cause any operational or tractor-trailer compatibility issues for most tractors.

It's the so-called safety advocates who are pushing for the 30 percent reduction, saying a changeover to air disc brakes is justified – damn the costs – for improved highway safety.

Members of the Heavy Duty Brake Manufacturers Council (HDBMC), the trade group representing many of the brake suppliers, are concerned about 30 percent shorter stops. Representatives from ArvinMeritor, Bendix and Haldex, the principal foundation brake suppliers, worry about the impact of significant weight transfer to front axles under such severe braking. Today's popular 151/2- by 4- inch S-cam front brakes would have to be upsized to 151/2- by 5- inch, or a changeover to much more expensive air discs.

HDBMC members believe a stopping distance reduction of 20 percent – even 25 percent – is achievable with today's brake systems and some upgrades. The group's other major concern continues to be the lack of standards or regulations for aftermarket replacement brake linings. Fleets and other big-truck users can inadvertently cause significant changes in brake performance and balance – and actually increase stopping distances – by relining brakes with materials that have different frictional coefficient values than what's on the vehicle.

What would major front brake changes cost? Depending on who you talk to, upgraded front S-cam brakes would likely cost $200-$250 per vehicle. A change to air disc fronts could be in the $1,600 to $2,000 range. However, the Truck Manufacturers Association says that NHTSA's cost estimates (about $170 million) are way too low because they don't include realistic costs for truck and brake manufacturers' engineering time or additional manufacturing resources needed to produce the products.