ELYRIA, Ohio –Not all stability systems are created equal. That’s the message contained in a comprehensive white paper on the subject, recently published by Bendix. The parts and component manufacturer has long been a vocal proponent of ‘full-stability’ or Electronic Stability Control (ESC) systems which protect against more out-of-control situations than just rollovers.

However, the company became alarmed when its own surveys suggested that while 81% of its dealer sales reps claimed to be familiar with stability systems, only 28% knew the difference between ‘full-stability’ and what Bendix calls ‘roll-only’ stability systems. Fred Andersky, director of marketing for controls with Bendix, said the same seemed to ring true with government officials and regulators, which prompted the company to publish the white paper.

“We’re really trying to take this information and help educate the market to understand first of all, that there are a couple systems out there, and that there are significant differences in those systems,” Andersky said during a conference call with media.

Roll Stability Control (RSC) systems utilize a lateral acceleration sensor to determine if a vehicle is travelling too fast to safely negotiate a corner. When a rollover is imminent, the system takes action to de-throttle the engine and apply the necessary brakes to prevent the truck from tipping over.

However, Andersky said roll-only systems have limited effectiveness, pointing to a study commissioned for the National Tank Truck Carriers that showed 53.2% of rollovers occurred on a straight road.

“Rollovers aren’t just rollovers,” explained Andersky. “It’s not the situation of a truck going around a turn too fast and flipping over. A lot of rollovers actually start with a loss-of-control type event.”

ESC systems include additional sensors to measure factors such as yaw rate and steer angle, so they not only read what the truck is doing, but also what the driver is attempting to make the truck do, Andersky explained.

“ESC includes a lateral acceleration sensor plus a vehicle yaw sensor and also adds sensors to measure driver input, specifically his steering input,” explained Rick Conklin, product manager for Bendix ESC. “It’s very important that full-stability systems understand what the driver wants the vehicle to do.”

In testing both ESC and RSC, Bendix engineers have used the term ‘Stability Margin’ (basically a driver’s margin of error) to measure the effectiveness of each type of stability system.

Since ESC can detect more than just potential rollovers, Bendix claims it can react more quickly and precisely, thus increasing a driver’s margin for error. In fact, Andersky said ESC provides a stability margin 2.5 times greater than RSC.

“If you only have the lateral acceleration sensor, braking is limited, they cannot achieve the same level of deceleration and the end result is they’re not as effective,” insisted Conklin.

To back its claim, Bendix examined the results of the US Federal Motor Carrier Safety Administration’s Large Truck Crash Causation Study. The study provided details of nearly 1,000 truck accidents.

While Bendix found about 130 of the 275 accidents where the trucker was at fault could have been mitigated or avoided by a stability system, 68% of those could only have been mitigated by ESC while RSC would only have changed the outcome in just 29% of the accidents.

By extension, Andersky reasoned that ESC has the potential to save nearly twice as many lives as RSC.

However, there’s still a significant price point differential between the two types of systems. While OEMs ultimately set the price, Andersky admitted ESC generally runs about US$1,600-$1,900 per truck while RSC can cost about half that.

“There are always going to be fleets out there that are going to be taking a look at the bottom line,” he admitted. “It really shouldn’t be a price decision, it should be a performance decision.”

He noted the price of ESC is less than 1% of the cost of a new truck and similar to the cost of a chrome bumper. Bendix has developed a value calculator fleets can use to measure a payback period.

Bendix engineers also acknowledged that even ESC has its limits, and won’t completely eliminate heavy truck accidents.

“(ESC) isn’t the end-all in and of itself,” said Conklin. “It’s not going to prevent every incident -the laws of physics still apply. We’re not going to make a bad driver a good driver, our intent is to make a good driver avoid a bad situation.”

Andersky added the system is designed to bail out the decent driver who makes a mistake. When an intervention occurs, it will “let him know he almost screwed up big-time, but he’s keeping the shiny side up and he’s going home for dinner that night.”

The timing of Bendix’s latest push for full-stability coincides with discussions that stability systems may be mandated on commercial vehicles. In the US, all passenger vehicles must be equipped with stability systems as of 2009.

National Highway Traffic Safety Administration administrator Nicole Nason has noted that only seatbelts have greater potential than stability systems in terms of saving lives and reducing injuries on the roads.

Andersky pointed out it stands to reason stability systems will be forced upon the commercial vehicle sector, where “large trucks are heavier, less stable and more prone to these types of situations.” NHTSA is currently evaluating both RSC and ESC to determine which, if any, type of system will be mandated.

Here in Canada, the Canadian Trucking Alliance is pushing for regulators to mandate the use of stability systems on all new trucks.

While Bendix has said it would prefer to see the industry adopt stability systems without government mandates, Andersky added “If we are going to mandate, let’s mandate the technology that’s going to help us today as well as tomorrow.”

The white paper, entitled Road Map for the Future: Making the Case for Full-Stability is now available at www. •