When the National Highway Traffic Safety Administration (NHTSA) finally issues its long-awaited rule shortening the stopping distance requirement for heavy-duty trucks, it'll be a very anti-climactic moment, says Alan Korn, chief engineer for Meritor Wabco. In fact, minor tweaks to current brake technology will enable a driver to stop a fully-loaded tractor trailer well within the 30% shorter distance

When the National Highway Traffic Safety Administration (NHTSA) finally issues its long-awaited rule shortening the stopping distance requirement for heavy-duty trucks, it'll be a very anti-climactic moment, says Alan Korn, chief engineer for Meritor Wabco. In fact, minor tweaks to current brake technology will enable a driver to stop a fully-loaded tractor trailer well within the 30% shorter distance that NHTSA's rule is expected to demand.

“We won't need breakthrough technology to reduce stopping distances,” says Korn. “In our opinion, current components — modified drum brakes combined with existing antilock braking system (ABS) technology — can do the job. It's not going to be an incredible challenge to meet the new regulations.”

Korn says the real issue is where heavy truck safety efforts go from here: Whether ABS and drum brakes remain the foundation upon which future truck safety advances in North America are based, or if electronically controlled braking systems (ECBS) and disc brake technology should become the new focal points.

“The reason for not jumping from one technology to another right now is that many heavy truck safety features, from traction control to rollover prevention, can now be enabled with ABS,” he explains.

Though the high speed of electronic signals clearly gives ECBS an advantage, “the difference between the capabilities of ABS and ECBS is no longer night and day, and that's making the transfer to the new technology difficult.”

Making this debate more volatile is a growing public perception that U.S. heavy trucks are lagging their European counterparts when it comes to safety technology, especially where brakes are concerned.

Statements like the following don't help the situation. “Europe is doing a decidedly better job in truck safety,” proclaimed Brian O'Neill, president of the Insurance Institute for Highway Safety, during a speech at the International Truck & Bus Safety & Security Symposium.

“The U.S. abandoned [its first] effort to mandate ABS in the 1970s at a time when U.S. manufacturers were the leaders in this technology. Instead, Europeans picked it up and they're now the leaders,” he contends. “ECBS is used widely in Europe and its been proven to reduce crashes in passenger cars. It is very, very efficient technology in terms of applying braking forces.”

O'Neill made no bones about the stance safety advocacy groups take when it comes to improving heavy truck safety in the U.S., either. “Clearly, Europeans are more vigilant than the U.S. when it comes to heavy truck safety,” he says. “The trucking lobby in this country pays lip service to safety; it treats safety as a nuisance, as it is far more concerned with economics.”

However, trucking contends that most of the heavy- truck/passenger-car crashes in the U.S. are the result of factors that are either well beyond the truck drivers' control or well beyond what technology could affect.

In a letter to Transportation Secretary Norman Mineta last year, Bill Graves, president and CEO of the American Trucking Assns., said: “Further research into these serious car-truck crashes has clearly indicated that the unintentional but unsafe actions of the passenger vehicle driver either causes or plays a significant contributing role in about 75% of the crashes.”


Direct comparison of U.S. and European truck safety technologies is not a meaningful exercise in the eyes of many experts because we're really comparing apples to oranges. Logic aside, comparisons have been made, leading to controversy on both sides of the Atlantic.

“You could start a real war of words by saying European trucks are better and safer than those in the U.S.,” says Ted Smith, founder and chairman of TSE Brakes. “European trucks are not better; they're just different. They are designed differently, they operate differently, and they are driven differently.”

For example, heavy trucks in Europe don't perform nearly as many longhaul, on-highway runs as tractor-trailers in the U.S., simply due to the limited size and scope of Europe's geography. They also tend to operate along extremely narrow city streets, necessitating a much tighter turning radius and use of curtain-side trailers for easier loading and unloading — operating demands that directly impact how brake systems need to function, Smith points out.

Randy Petresh, vp-technical services for Haldex Brakes, also points out that in Europe, truck design is completely OEM-driven; customers have little say in terms of vehicle specs. “That completely changes the design approach to the vehicle,” he explains. “In Europe, new systems can be added to a vehicle regardless of customer input. In the U.S., you must first convince the customer it is better.”

“Europe started with a more complicated truck platform than the U.S.,” adds Jim McClelland, vp-original equipment sales for Bendix. “That almost necessitated choosing ECBS simply because they started from a very different design point than U.S. commercial trucks.”

TSE's Smith says it's “a little disingenuous” to equate design differences to stopping distances. “European tractors have two axles, while those in the U.S. have three; the reverse is true for trailers.”

With only two axles, European trucks must deliver more power,” Smith points out. “That's one reason air disc brakes are much more critical to European trucks; those axles are loaded far heavier.”

Air-line pressure requirements represent another difference between vehicles in the two continents. In Europe, the braking system uses 147 lb. of pressure, while in the U.S. it's 100 lb. “You can get a whole lot more braking power with more pressure; for starters, you can push a whole lot harder on the brake shoe,” Smith notes.

“But by the time you get down to the actual amount of friction being applied by European and U.S. truck brakes, you really end up with about the same amount of stopping power.”

Another twist in the debate over truck brakes comes out of NHTSA's 1995 decision to mandate the use of ABS on heavy trucks. That decision, says Meritor Wabco's Korn, computerized the control of truck brakes to a major extent, in some ways stealing ECBS's thunder.

“Now we suddenly had a platform where we could offer roll stability control and collision mitigation,” he says. “We also found that ABS was not limiting from a technological standpoint. We could and have evolved the system to offer new capabilities for improved truck safety. Truck safety is not sacrificed by staying with ABS and current brake technology.”

“The end result is that we can add in safety features without blowing up the current ABS architecture,” explains Bendix's McClelland. “It allows the truck OEMs to retain a lot of flexibility in terms of adding safety systems without adding too much extra cost.”

And because ABS requirements were phased in, OEMs had time to improve the technology even further. Tractors were required to have ABS by March 1, 1997; air-braked trailers and single-unit trucks and buses had a deadline of March 1, 1998; and new single-unit trucks and buses with hydraulic brakes were given until March 1, 1999.

As the gap between ABS and ECBS brake activation times began to narrow, it became even more difficult to convince people that a move to ECBS technology was necessary.

“When all is said and done, you're talking the difference between 2/10th and 3/10th of a second in terms of brake activation between these two technologies,” says Haldex's Petresh. “In real-world terms, what's the value of an extra of 1/10th of second? That's why measuring the safety benefits of one system versus the other is almost impossible.”

And with ECBS-based technology priced any where from $1,000 to $2,000 more than its ABS counterparts, it becomes even harder to justify. “If safety isn't being sacrificed, then price sensitivity becomes the determining factor,” says Korn. “It gets harder to show payback when you're talking stopping distance differences of 20 feet in some cases.”

“Cost and reliability have to be factored in,” says Dr. Robert Schumacher, general director for advanced product development and business strategy at Delphi. This is especially true in an industry where the difference between profits and losses is measured in pennies.

“First, the technology must be absolutely mature; it must be bulletproof, fail-safe, and absolutely reliable. There also must be a business case to support it,” he says. “Fleets need to see a payback; the cost savings for the extra investment must be there.”

“Half of all truck-related accidents are in the forward direction, and that's where the bulk of the fatalities, injuries, and property damage occur,” Schumacher says. “So the biggest bang your going to get for your safety buck is going to be spent on forward-looking safety devices, followed by anti-rollover systems.”


That's not to say that ECBS has no future in the U.S. truck arena. Some even see it as an eventual replacement for ABS-controlled systems, simply because as more and more safety systems are added to heavy trucks, ECBS may become the most cost-efficient platform for tying them all together.

“Rollover stability control, traction control, and adaptive cruise control all require active braking to function at peak efficiency — and active braking requires electronic control,” explains Haldex's Petresh.

“Once you get an electronic platform in place, it's much easier to integrate the safety technology into a vehicle. ABS requires a much more piece by piece infrastructure in order to gain those capabilities, including additional solenoids, valves, and connectors,” he says. “ECBS offers a much more efficient platform to add on more safety functions.”

Korn sees ECBS as “higher performing” rather than “better.” He explains: “It gives the braking system more ‘intelligence,’ allowing you to balance brake use axle by axle — even wheel by wheel — so you get more even lining wear. The sensors at all the wheel ends also give you more diagnostic capability, so you can monitor and maintain braking performance better.”

Korn adds that when the performance, diagnostic, and upgrade advantages of ECBS come together, it will become the lower cost option. That's when the industry will switch to ECBS-based platforms.

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.