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Stability mandate on the way, officials claim

TAMPA, Fla. – Panelists discussing truck and trailer stability systems at this year’s Technology & Maintenance Council meetings agreed it’s just a matter of time before the systems are mandated in North America, but the...


TAMPA, Fla. – Panelists discussing truck and trailer stability systems at this year’s Technology & Maintenance Council meetings agreed it’s just a matter of time before the systems are mandated in North America, but the type of stability system required and the timing of a mandate have “yet to be determined.”

Tom Weed, engineering supervisor, ABS, with Bendix said there’s plenty of reason to expect a stability system mandate from the National Highway Traffic Safety Administration: there are 200,000 systems on North American roads today and they work well; Europe has mandated stability systems; and NHTSA already has mandated stability systems on passenger vehicles.

What’s still unclear, however, is what type of stability system will be mandated and when. There are two types of systems available on the market today: electronic stability control (ESC) and roll stability systems (RSS).

Weed said roll stability systems can protect against vehicle rollovers, but they do not prevent loss-of-control events, where a tractor-trailer jackknifes. ESC not only prevents rollovers, but also uses additional sensors to detect when a vehicle is about to lose control, dethrottles the engine and applies the appropriate brakes to bring the unit back in line. Roll stability systems take the same corrective measures to prevent rollovers.

Weed noted rollovers tend to occur on dry road surfaces as a vehicle is turning; the tires typically have a good grip on the road surface and they resist the lateral acceleration resulting in a rollover. On the other hand, loss-of-control-type accidents tend to occur on wet and slippery road surfaces.

Rollovers, Weed noted, are more predictive in nature and as a result, a stability system will typically intervene more often to prevent rollovers than loss-of-control events.

Weed pointed out all stability systems can “only be effective within the limits of physics.”

He added “They can’t make a bad driver safe, but they can help a good driver return home,” noting even good drivers make the occasional mistake.

One believer in the technology is Todd Cotier of Hartt Transportation Systems. After suffering four costly rollovers in the past eight years (with losses ranging from $195,000-$250,000 per incident, plus the loss of a new account), Hartt began spec’ing stability systems on its new vehicles. While it’s early – the new trucks have only been in service for about six months – Cotier said the fleet hasn’t yet suffered a rollover since putting the stability system-equipped vehicles into service.

Cotier said he’s now working with providers to deliver notifications of intervention events to management in real-time, so it can quickly engage the driver and offer remedial training if necessary.

That is not an unusual request, Weed noted.

“Some managers want an instant e-mail when an event occurs,” he said. “It doesn’t give the driver time to build up a story.”
Still, with stability systems becoming increasingly prevalent, there are some maintenance-related issues that have arisen.
For one, technicians need to be trained on the systems and will have to be comfortable with PC diagnostic software programs, pointed out Matt Williams, manager sales, service and training with Meritor Wabco Vehicle Control Systems.
He said diagnosing stability systems is more complicated than analyzing blink codes.

“Technicians will need PC diagnostics to go in and get this onboard data,” he warned. “Technician training is paramount.”
Fleets will also have to determine exactly how much data they wish to receive and how they wish to receive it, as well as develop a plan for what they intend to do with that data.

When certain components are replaced or serviced (a suspension or steering column, for instance), the systems have to be recalibrated. This can be done with the help of PC diagnostic software.

One fleet manager in attendance wondered if it was acceptable to change tire types, and was assured tires are completely interchangeable as long as the size remains consistent.

Williams stressed tractor stability system retrofits are not permitted, due to the high level of communication between the system and the vehicle’s electronic control unit (ECU). Trailer retrofits, however, are possible.

Weed advised technicians to contact the OE before modifying a vehicle and to avoid moving the yaw rate sensor and lateral acceleration sensor.

Lastly, Weed warned fleets implementing stability systems into their fleet to train drivers and to avoid the temptation to “road test” the system by intentionally triggering interventions on the highway.

“It’s not a good idea,” he stressed, adding demonstrations in controlled environments are available through the suppliers.


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