My first encounter with the system was disconcerting. I was driving a new Toyota Sequoia SUV one drizzly morning and about to enter a major road near my home. As I turned into the intersection, the rear wheels started to slip on the wet pavement. That's when the stability control system kicked in, cutting the power so that the wheels nearly came to a stop. My first thought was that something was wrong with the SUV, and I got worried as I looked to my left and saw a car bearing down on me. Then I realized that the beep I was hearing was actually an alert, letting me know that the stability system had been activated. A few seconds later, the wheels gripped the road, and the Sequoia took off at a normal speed. I was never in actual danger, but the experience was unsettling.
Despite my momentary fear, electronic stability control is a worthwhile--and potentially life-saving--feature. It can prevent a car from skidding off the road or even rolling over. In 1999, auto supplier Continental Teves, which makes half the stability control systems worldwide, sold about 400,000 units. This year, it will sell nearly 1.5 million. In 2003, the company's unit sales are expected to hit 3.5 million. Carmakers use different terminology--Ford (F
) prefers AdvancedTrac, while Toyota (TM
) uses "vehicle skid control"--but the systems all do basically the same thing.CAUSE FOR ALARM. When the stability control system works best, you don't even know it's there. It applies brake pressure to individual wheels as the tires lose their grip. A wheel that's slipping will move faster than the vehicle, so sensors constantly measure the wheel speed and the position of the auto. When a vehicle starts to slip out of line, the control system can even slow down the engine. Because the system doesn't let the vehicle slip or skid, you find out that the road is slippery only when a light on the dash tells you the system has kicked in or when the alarm beeps. Except in extreme cases where the engine slows sharply, the result is a much safer-feeling ride. "Every vehicle ought to have this technology, especially SUVs," says David Champion, director of the auto-test department for Consumers Union, publisher of Consumer Reports. In the future, new systems might even make small adjustments to the steering to avoid a collision.
Drivers need to understand these new safety systems. Antilock braking systems took a while to catch on because people didn't know how to use them. Many drivers panic when they feel the pulsating sensation of ABS in their leg. Their reaction is to take their foot off the brake, which can lead to more accidents. Meanwhile, some people drive more aggressively when they feel protected by added safety systems, which then cancels out the benefit of the new technology. What's more, carmakers have varying philosophies for stability systems. The system in a Toyota or a Mercedes clamps down hard, allowing no slipping at all. In a Chevy Corvette, more of a performance car, you encounter some sliding so you can get a better feel for the road. "It depends on the kind of feel the auto maker wants," says Mark Sowka, vice-president for electronic brake systems at Continental Teves.
In most cases, you just need to know what sort of system is installed in the car, so you have an idea what to expect. Often, there is no detectable change when the system kicks in. But should your car abruptly lose speed on a corner, it just may be the stability control system telling you to slow down. By Jeff Green