Truck News


The Rolling Stop?

TORONTO, Ont. - It appears that everything old can be new again - even when you're updating manufacturing standards for commercial vehicles.

TORONTO, Ont. – It appears that everything old can be new again – even when you’re updating manufacturing standards for commercial vehicles.

When the U.S. National Highway Traffic Safety Administration (NHTSA) unveils plans to shorten allowable stopping distances for trucks, the proposed numbers will approach the limits that were originally suggested in 1970.

About 35 years ago, regulators south of the border had wanted buses, empty straight trucks and bobtailing tractors to stop from speeds of 60 mph within 216 feet, mimicking light vehicle stopping distances.

But industry lobbyists, arguing that equipment of the day wasn’t up to the challenge, managed to convince NHTSA to alter the requirements to stop empty buses within 280 feet and bring empty trucks to a rest within 335 feet.

Those requirements are still in place today. The distances to be proposed under a pending Advanced Notice of Proposed Rule Making (ANPRM), one of the first steps in the U.S. regulatory process, are largely expected to be 30 per cent shorter than those allowed under current guidelines. And that could require the use of larger S-cam brakes or disc brakes on steer axles.

“That’s a goal – if you don’t set a goal, you don’t reach it,” says Jim Britell of NHTSA’s Office of Vehicle Safety.

The latest NHTSA proposal has hardly been a snap decision. Discussions about shortening the allowable stopping distances began several years ago, related tests were conducted last year at the agency’s Vehicle Research and Test Center in East Liberty Ohio, and the ANPRM – usually pronounced “an-pram” – was originally scheduled to be unveiled in 2003. Britell noted during TMC’s spring meeting that he expected a final document by the end of May, but it’s now looking more like the end of July.

Even when it is introduced, the industry will have 90 days to comment on the proposal before regulators begin to draft their final rule. And it generally takes about two years for an ANPRM to work its way through the agency before becoming an actual requirement, while the rules themselves can be introduced over a staggered period of time.

Transport Canada, meanwhile, tends to mimic U.S. manufacturing standards once they’re in place. Still, the issue isn’t likely to be forever bogged down in bureaucratic red tape. Last year, NHTSA listed tractor-trailer stopping distances as one of its top highway safety priorities leading up to 2006.

The agency contended that truck brake performance is a “major factor contributing to crashes involving large trucks,” and suggested that a final ruling could come as early as next year.

Research is also scheduled to begin on straight trucks and buses, with a plan to address that equipment by 2006.

While NHTSA has already noted that such shorter stopping distances can be achieved using disc brakes or more powerful drum designs on steer axles, it will be up to manufacturers and the trucking industry to offer the specific tools for the task.

The regulator doesn’t plan to specify the type of required equipment changes, Britell says.

That stance is noticeably different from the one taken in the mid-1990s, when NHTSA introduced plans for mandated anti-lock braking systems along with a requirement for a second electrical connector between tractors and trailers. After an outcry led by manufacturers and groups such as the Technology and Maintenance Council (TMC) of the American Trucking Associations, the industry convinced the regulator to allow for another solution.

That came in the form of today’s “multiplexed” J560 pigtails, which use a traditional connector’s seven pins to power such things as in-cab warning lights, ABS systems and other auxiliary equipment.

“We had a little flap in there with the other connector,” Britell admits.

But equipment will undoubtedly need to be updated. About 98 per cent of drum brakes are S-cam designs, Paul Johnson, senior director of ArvinMeritor’s North American brake business, explained during a spring TMC session concerning the issue. But the brakes come in different sizes.

Sixty per cent of steer axles incorporate 15-inch cams, compared to 37 per cent that use 16.5-inch designs, he said. And that offers an important difference in stopping power.

Tractor-trailers with a Gross Vehicle Weight Rating (GVWR) of 52,000 lb. currently need to stop from speeds of 60 mph within a distance of 355 feet – a requirement easily met by either size of brakes. But problems emerge if the allowable distances are shortened to 248 feet, since trucks equipped with 15×4 brakes on steer axles will only come to a rest within 244 feet. A 16.5×5 brake on a steer axle will bring the truck to a stop within 206 feet.

The use of disc brakes will shed about 10 feet from the minimum stopping distances enjoyed by trucks equipped with one of the larger S-cam designs.

Whatever solutions are found, manufacturers will want to ensure a comfortable compliance level, Dana Corp.’s Jim Clark suggested during the same session. “Manufacturers want a 10 per cent margin.”

But perhaps one of the biggest changes could come with the ANPRM’s anticipated references to maintenance practices and vehicle speeds. While NHTSA generally limits discussions like these to equipment, agency officials are being encouraged behind the scenes to work closer with their counterparts in the Federal Motor Carrier Safety Administration (FMCSA), a senior government official has told Truck News.

Maintenance-related issues have long been at the root of out-of-service defects affecting brakes.

More than 16 per cent of the brakes inspected during last September’s Operation Air Brake were found to be out of service, with 11 per cent of the 14,665 inspected units found to be out of adjustment.

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