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The challenge of ABS

By: staff

Date: 1994-06-05

This article originally appeared in Volume 4, Number 2 of Driver/Education, in June 1994.

Some automobile advertisements seem to present the antilock braking system (ABS) as a sort of magic solution to the average driver's poor braking skills. The drivers in the ads stop short of children who dash into the roadway, and neatly steer around obstacles to avoid collisions. Engineers hail ABS as perhaps the greatest safety advance in decades. But a recent report by the U.S. Highway Loss Data Institute , which represents insurance companies, stated that antilock systems aren't reducing either the frequency or the cost of crashes that result in insurance claims for vehicle damage.

Getting the best from ABS Antilock braking systems don't offer shorter stopping distances. In fact on loose surfaces, where gravel or loose snow can form a wedge in front of the tire, ABS is a disadvantage. Drivers skilled at threshold braking can equal, or even outdo, ABS at stopping short. What ABS really excels at is allowing maximum braking while maintaining steering control.

For drivers unused to ABS, the important thing is to experience how it feels and how the car reacts in a controlled environment. Some drivers have reported that they were scared by the sound the brakes make when ABS was in action, and instinctively released the pedal. And drivers tend to react with old habits when faced with an emergency-for example by pumping the brake pedal while stopping on slippery surfaces.

"Don't wait to discover how your car will respond when faced with an emergency situation," says Sgt. Graham Austin, head of Police Vehicle Operations in Metro Toronto. "Find various surfaces in safe areas and experience the handling capabilities of ABS."

Insurance Institute for Highway Safety president Brian O'Neill advises drivers to use firm, continuous brake pressure. Others, such as Petro Canada Skid Control School manager Doug Annett, say "slam" the pedal and keep it down, letting ABS do the rest. Most importantly, don't pump the pedal while doing emergency braking. This is the ABS's job. And it does it very well.

Can it be that one of the best developments in auto safety engineering in decades has produced no benefits in terms of reduced deaths, injuries and repair bills from crashes?

By all accounts this seems to be the case. In January this year the Virginia-based Highway Loss Data Institute (HLDI) released the results of a study on ABS effectiveness in reducing collisions. The study found no significant payoff in terms of deaths, injuries or lower repair bills for cars equipped with ABS.

Some states have been offering insurance discounts for cars with ABS, but many in the insurance business didn't seem to be surprised by the HLDI results. "We never felt there was any strong evidence ABS reduces the number of accidents," State Farm Mutual Auto Insurance spokesman David Hurst told the New York Times recently. "We offer discounts only because we're supposed to, not because we feel they're justified," he added.

There appears to be a number of reasons why ABS hasn't produced the promised safety payoff. One is that many drivers don't understand them or know how to use them properly. Another reason, and one that's received a great deal of attention in research circles, is that ABS seems to produce a behaviour change in some drivers. They drive faster, more recklessly, take more chances.

The classic study of this phenomenon was carried out in Germany in the early '80s. The German Ministry of Transport commissioned a multi-year study of taxi drivers using vehicles with and without ABS. In one phase of the study, without the drivers knowledge, accelerometers were placed in the vehicles to record the abruptness of changes in speed and direction. It was found that drivers with ABS made more abrupt changes. In another phase, observers were sent out to ride with the drivers and note their style and other driving characteristics. The observers had been trained until they were in close agreement in their judgments of driver behaviours, and told to ride with the drivers from one point to another, a distance of about 20 km.

"It was a beautiful case of a double blind study; a textbook example of how it should be done," says Queen's University psychologist Gerald Wilde, one of the consultants on the study.

"The observers didn't know whether or not the vehicles had ABS, and the drivers didn't know they were being observed." Driver behaviours on about 20 different scales (for example, merging behaviour, speed, following distance, lane tracking, whether they created traffic conflicts) were recorded by the observers. "On some 13 of those scales, or at least the large majority, there were some significant differences. ABS cars were driven more recklessly," says Wilde. "We offer discounts only because we're supposed to, not because we feel they're justified."

Wilde cites the study in support of his theory of Risk Homeostasis, a concept that is widely known in traffic safety circles and often hotly disputed. The theory asserts that every society has a kind of danger thermostat, that there's a level of risk people will accept in exchange for the benefits of their way of life. A new device that makes an activity safer, Wilde postulates, will result in a collective increase in risky behaviour. In other words, people know the level of risk they'll accept in their lives, and if given a device such as ABS, they'll use up its benefits by changing behaviour in such a way as to return to their "target level" of risk. (Wilde's book Target Risk 2 was released in 2001.)

Certainly the research seems to confirm that ABS produces some kind of risk compensation effect in drivers. A more recent study of ABS by Transport Canada had similar findings to the German one, and a French study involving 100 Renault employees is of particular significance for driver trainers. This study found that drivers trained in the use of ABS performed better in a simulated collision avoidance task.

There are about 10 million ABS-equipped cars on North American roads today, according to the Insurance Institute for Highway Safety (IIHS). The device is popular with the public but this, says the IIHS, may be because of misleading car commercials that imply better stopping power under all conditions. And in some cases even the owner's manuals that come with the cars can be misleading. Some manuals give no special instructions at all while one offers the misleading statement that its ABS functions with normal pedal operation. Some auto makers are also considering special training programs for their customers on the proper use of ABS.

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