Stomping on ABS

Industry engineers have expounded the virtues of skid-free antilock braking systems (ABS) since their mid-'80s U.S. production-car debut. High-performance driving instructors and other vehicle-dynamics experts admit that ABS can make what is perhaps the most difficult of vehicle-control maneuvers -- achieving maximum braking at the threshold of wheel lockup -- a no-brainer for even average drivers.

Trouble is, ABS and average drivers don't appear to be fully compatible.

A January 1994 study from the Highway Loss Data Institute (HLDI) comparing accident statistics for a variety of General Motors Corp. vehicles equipped with ABS found them to be statistically no "safer" than the same vehicles not fitted with AB S.

An even-ternpered read on the situation was provided at the time by Arvin F. Mueller, GM vice president and general manager -- NAO Technical Center: "Anyone who has evaluated the (ABS) system knows it works exceedingly well," he explains, while offering that many drivers of ABS-equipped vehicles really don't understand how to exploit the technology to its fullest.

An Insurance Institute for Highway Safety (IIHS) report on ABS effectiveness supports Mr. Mueller's analysis, citing a French ABS experiment with 100 drivers who had received varying levels of ABS training. In that experiment, knowledge of and experience with proper ABS driving techniques yielded small but tangible accident-reducing results. More important, the French researchers noted a curious behavior: not a single one of the 100 drivers, on the first training opportunity to try straightforward emergency braking, hit the pedal hard enough to engage the ABS system. The IIHS report says, "Researchers speculate this was because of `a high level of conditioning to normal braking and the fear of locking the wheels.'"

Uh-huh. Now we have it, concrete proof that drivers: a) aren't sure of how ABS works, and b) are too instinctually "conditioned" by years of caressing the brake pedal to give it the damn-the-torpedoes stomp that allows maximumabs-directed emergency braking.

But that's not quite all of it.

The insurance industry says automakers have "oversold" the benefits of ABS, causing drivers to expect stop-on-a-dime, physics-defying miracles. Predictably, these same oversold customers are now blaming ABS for the accidents in which they're involved. Currently, the National Highway Traffic Safety Admin. is entertaining a combined 10,000-plus consumer complaints alleging faulty ABS systems on a variety of GM and Chrysler Corp. vehicles.

Privately, product-development engineers grouse that the AB S brouhaha would vanish if vehicle owners took the time to study and understand the features of their new vehicle. And automakers concede it would be beneficial -- though difficult -- to perhaps devise a method of "demonstrating" ABS to each new owner.

But in reality, neither is likely to happen. So engineers are scheming new ideas that may make ABS even more user-friendly.

First, one braking system supplier tells WAW that engineers are working to "factor out" the sometimes distracting pulsation of the brake pedal when ABS engages. ABS applications vary widely in this area: some provide a light, highly refined tick-tick-tick brake pedal pulsation, while others buck and spit like an oil-starved chainsaw; drivers unaccustomed to ABS often reduce brake pedal pressure when they feel the pedal kicking back -- hardly an ideal emergency braking habit.

Further extensions of ABS enhancement, such as the various vehicle-stability systems now coming to market (see WAW -- April, '95, p.53), may make loss-of-control accidents less frequent. These systems selectively brake individual wheels to introduce more dynamic stability in certain situations. Although ABS has proven to reduce several types of accidents -- particularly wet-road and vehicle/pedestrian incidents -- researchers have noted that San increase in ABS-equipped vehicles that run off the road. It is these single-vehicle accidents that AB S enhancements like stabilitys-control systems may help to reduce.

And several automakers and suppliers are working on high-tech brake-proportioning setups that would supplement ABS by introducing even more "stability" to hard braking maneuvers. The more sophisticated designs incorporate a radar sensor that measures the distance and closing rate from once vehicle to the next; if the distance between the vehicles becomes dangerously thin, or closes too rapidly, the system will initiate braking, eliminating the critical few microseconds that it takes an inattentive driver to realize trouble's brewing.

Radar-initiated braking may be well into the future for the real world, but ongoing development of brake-proportioning systems that sense the pressure and rate of depression on the brake pedal have a more immediate appeal. By sensing how hard and how quickly the driver stabs the brake pedal, the system can be programmed to "take over" the braking if the algorithms decide it's an emergency situation. Since it's already well-documented that most drivers don't hit the pedal bard enough in true emergencies, this type of system would intervene -- assuring not only maximum braking effort but also that ABS is likewise engaged.

Whether new technology will help or only serve to further hinder the effectiveness of ABS is anybody's guess. As one development engineer says, "The driver/ vehicle interface is delicate. We don't know nearly enough about how much sophistication in that relationship is too much."