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Faulty ABS warning systems common problem, study reveals

TORONTO, Ont. - One in every three trailers and one in 10 tractors are operating without working ABS warning systems, a recent study by the U.S. Federal Motor Carrier Safety Administration (FMCSA) has...

TORONTO, Ont. – One in every three trailers and one in 10 tractors are operating without working ABS warning systems, a recent study by the U.S. Federal Motor Carrier Safety Administration (FMCSA) has discovered, and the biggest problem tends to be missing or inoperative warning lamps.

The findings presented during a recent meeting of the Commercial Vehicle Safety Alliance (CVSA), which sets vehicle inspection standards across North America, were based on a random sample of 1,000 commercial vehicles studied in Pennsylvania, Washington, California and Ohio.

“That’s pretty stunning,” said Rolf Vanderzwaag of the Ontario Trucking Association, who was one of the officials who heard the results for the first time.

The research initiative had been launched in response to anecdotal reports of problem warning systems – and the reports appear to be well founded.

“About one in four ABS lamps were inoperative, while 23 per cent of post-2001 power units were missing trailer-related warning lamps, or (had) lamps that were inoperable,” the study concluded, referring to some of the specific problems. Researchers also found an increasing trend of active faults in power units built within the past four years. “This indicates that the enhanced driver interface may not be utilized as intended by the regulations.”

In-dash warning lights have needed to indicate trailer-related ABS faults since March 1, 2001, as a way to warn drivers about the potential of locking wheels.

As simple as it sounds, it took a massive engineering effort to find a way to light the little bulb in the first place. When the U.S. government first announced plans to mandate the warning lights, the trucking industry already had uses for each of the seven pins in the connectors that feed electricity between tractors and trailers. There was no space for the signal to power the warning light, and many industry officials wondered whether there would be a need for a second power cord.

In the end, the solution involved developing a communications standard (PLC4TRUCKS) that allows signals to hitch a ride on one of the wires fed with a constant source of power. The resulting “multiplexing” systems allow the cab to communicate with a litany of trailer-based systems, ranging from ABS to onboard scales and reefer units.

The recent study found that problem sensors, controllers or ABS computers were blamed for lamps that glowed regardless of whether a problem existed on four per cent of tractors and eight per cent of trailers. Such problems could be caused by wiring problems on the circuit that powers the lamp. In addition to that, 12 per cent of tractors and 29 per cent of trailers could be oblivious to an actual fault because of missing or inoperable lamps.

“Now they have to decide what to do about this,” Vanderzwaag said.

Authors of the study have asked for the warning systems to be added to the checklists during CVSA Level 1 inspections, and want a DOT policy statement to encourage enforcement.

“In the current inspection procedure, (the warning system) is sort of an afterthought,” admitted Luke Loy of the FMCSA’s Vehicle and Roadside Operations Division, who presented the findings. “It’s not emphasized too much and I don’t believe it’s really checked…We’re thinking some additional attention needs to be there.”

Still, Loy said it’s unlikely that the problem warning systems would ever be added to the out-of-service criteria that can actually ground defective equipment. “The backup systems are there,” he said, noting that equipment without ABS still has functioning brakes.

But with an inactive system, drivers may not be aware of the potential jackknife situation that can come if wheels lock up during a panic stop.

The report also indicates a need for more education about where lamps should be located. “It was not uncommon for the parking brake icon, ABS icon, and automatic traction control (ATC) icon to be located adjacent to one another on the dashboard and of the same amber color, with only the characteristics in the middle of the circle different, and thus sometimes hard to distinguish.”

The location of the warning lights can be found in a number of locations. In Peterbilts, for example, the lamps are in the centre of the dash, above the steering wheel, International shows it in the vertical light bar in the right instrument cluster, with the trailer icon in the left cluster, while Freightliner puts the icon in the far right of the light panel above the speedometer.

Loy, meanwhile, leaves little doubt that the study is large enough to be taken seriously.

At 1,000 vehicles, he said, “it seems like a pretty good sample size.”

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1 Comment » for Faulty ABS warning systems common problem, study reveals
  1. Val Weist says:

    This study does not represent findings from the actual driver based and field service findings because it is common knowledge to all levels of operations that; as soon as a unit leaves the factory and sees the first winter and rain seasons you will see random and prolonged warnings from the system and after a couple years the dam lights get disconnected. This system overburdens the maintainence time on units and it sure be nice if we could just practice better operating instead of relying on ABS. I have found a couple of other common problems that do represent some merrit to this study. Poorly mounted/broken sensor wiring, intermittant signal connections to traillers(especialy super bs) at power cords and issues encounters from rough roads and poor traction in winter when chains have been used. 14 yrs experience on mountain winter driving, British Columbia, CA

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