Safety Technology: Rollover Control


November 2008, - Feature


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Not a lot of truck buyers are choosing electronic stability enhancement devices, but maybe they should - because they could be saving big bucks. One supplier estimates that about 14 percent of those purchasing heavy trucks and tractors specify the option. The rest pass on it, probably because they don't know anything about it. And even if they do, they don't like the $2,000 to $3,000 upcharge. In troubled times like these, anyone who's buying new trucks tries to keep purchase prices as low as possible.

That might be false economy. Some of the most financially hard-nosed fleets are spending the extra money on this safety equipment and are seeing a healthy return on their investments. The money comes back via crash prevention and, in at least one case, by reduction in driveline maintenance. Sometimes the savings are difficult to quantify - how do you put dollar numbers on accidents you don't have? - but savings can be inferred and valued based on experience.

Electronic stability and anti-rollover products from three suppliers were developed in Europe and adapted for use here. Among other things, units sold here run on 12 volts instead of 24, and their software is designed for North American vehicles, which have different axle configurations and centers of gravity than those of European rigs. Writing the software is time-consuming and must be verified by testing actual vehicles.


The devices piggyback on electronic controls and sensors already used by anti-lock braking systems now standard on air-braked trucks, tractors and semitrailers. A roll-control type concentrates on center of gravity and g-forces caused by hard braking and sudden lateral movements. Stability control products have additional sensors to measure steering input and yaw, or side-to-side rotation.

When the electronic controls sense an impending slide or roll-over, the devices cut the engine's throttle and apply brakes to slow a vehicle and get it back under control. The systems react in milliseconds and it's all over in a second or two, usually before drivers realize what's happening. Drivers are often reluctant to report any stability or roll-control intervention because they don't want to get into trouble ("Ha ha, I almost rolled 'er, but that gizmo got me outta it!").

However, the devices will usually record such events and have the data ready for downloading, if managers want to bother with it. If they do, they can counsel drivers; if not, they're getting less than full value out of the equipment, though it's still probably preventing accidents.

The products go by various names:

Electronic Stability Program (ESP), also called Electronic Stability Control (ESC), from Bendix Commercial Vehicle Systems. This is an option on various models from Kenworth and Peterbilt, and it's standard on highway tractors and mixer chassis from Volvo and Mack. Those two builders hang on their own names - Volvo Enhanced Stability Technology (VEST) and Mack Road Stability Advantage (RSA).

Roll Stability Control (RSC) for trucks and tractors, from Meritor Wabco. This is optional from Freightliner, Sterling, Western Star and other builders who use Meritor Wabco ABS. It also makes Roll Stability Support (RSS), which can be spec'd on many new trailers. RSS monitors lateral movements and forces in the braking system and air-bag suspension, and applies a trailer's brakes during dangerous maneuvers to keep it from rolling over and pulling the tractor with it.

Trailer Roll Stability (TRS) from Haldex Commercial Vehicle Systems. TRS is available from some trailer builders. TRS watches what the Haldex anti-lock braking system does and observes pressures in the air bags, then quickly reacts when it sees an impending rollover by applying the trailer's brakes. Trailer-only systems are valuable because drivers cannot feel what their trailers are doing, Haldex says. Oversteering by a driver can send a trailer into a rollover, and by the time he or she sees it in the mirrors, it's way too late to do anything but hang on.

That's true of tractor rollovers and jackknifes, too, says Jeff Hall, president, J&R Hall Transport, Ayr, Ontario. While ABS is thought of as an anti-jackknife device, sometimes it alone can't stop jackknifing on very slick and uneven road surfaces. In winter of 2005, the 70-tractor fleet, whose rigs run regularly to western Canada, had three weather-related jackknifes, so Hall decided to go with Bendix ESC on his Kenworth T600 tractors. He had seen it demonstrated and was so impressed that "we couldn't get our hands on it fast enough."

Jackknifes have been all but eliminated, and so have a lot of insurance claims. Hall continued ordering ESC and it now comes on new T660s. About 45 of his tractors now have it, and all will in the near future. Drivers were at first miffed because they consider themselves professionals, he said, but they accepted it after supervisors explained how ESC works.

Schneider National Carriers generally doesn't spend a dollar unless it can get back at least $1.15, says Don Osterberg, vice president of safety and driver training at the giant fleet's headquarters in Green Bay, Wis. And it's getting back far more than that with the Meritor Wabco Roll Stability Control systems it began buying on its Freightliner Century S/T tractors in 2004. Now nearly all of its 15,000 tractors have RSC.

"We constantly track our safety performance in several categories and sub-categories," Osterberg explains. "And in 2003, our rollover rates were somewhere in the neighborhood of five rollovers per 100 million miles. Now that doesn't sound like a lot" - until you think about the fact that the fleet runs 1.5 billion miles a year - "but we decided to go with Roll Stability Control. There are a number of different types of rollovers; exit ramps and highway curves were the two most typical caused by speed being too fast. By 2008, we've seen a 40 percent reduction in the rollover rate."

The mean cost of Schneider's rollover accidents - half cost more and half cost less - is $20,725, Osterberg said. For jackknife accidents it's $1,362; he credits RSC with reducing those and certain other loss-of-control crashes by 35 to 40 percent. "So we've been delighted with the performance of those systems, and I wouldn't spec a truck today without it."

There are maintenance benefits, as well. "Beyond the safety aspects - and this is one of the unexpected functionalities - we've reduced our drivetrain damage by 50 percent," Osterberg adds. "This is because drive wheels would spin on ice and then come in contact with pavement," damaging U-joints and differential gears. RSC reduces engine power and applies brakes if necessary when drive wheels begin spinning, so they're back to rolling at vehicle speed when they hit dry pavement, and diff gears also continue rolling without being shocked. This saves about $150,000 per year.

As to the return on any investment, "In many cases you want to get as much as you can, and you want to get it back as quick as you can," Osterberg says. "It's different for safety, and if it's that alone, you default to safety. We have a core value of safety, but let's face it, we're in business to make money and we have an obligation to." Careful analysis predicted ROI would be about 70 percent with Roll Stability Control, and Schneider executives have not been disappointed.

That not everyone wants the electronic stability enhancement systems is evident to Terry Garsey, sales manager at Indiana Truck Sales & Service, the Mack and Volvo dealer in Indianapolis. "Volvo is all about safety," he says, "and so it's standard on all highway tractors, and it's non-deleteable. That's good in a way, but when you're trying to sell trucks to a fleet guy who isn't interested in it, and it's built into the price and he doesn't want to pay for it, it makes it kind of hard to bid on the deal."

Yet he has sold tractors with the Bendix stability control, he said, including a group of Macks to a food-grade tanker fleet last June. "And I haven't heard much back about it, except a story about one driver who complained that the system was applying the brakes in a tight curve that he liked to take kind of fast. So I guess the thing is working like it should, even if the driver didn't like it."

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