by Tony Whitney

I’ve often emphasized the benefits of electronic stability control systems and pointed out just how much safer today’s vehicles are with this kind of technology. These systems are usually standard on upscale vehicles, optional on mid-priced products and sometimes available even on fairly inexpensive models.

Most of the benefits of stability control are obvious – if a vehicle can be “automatically” brought back under control when a skid or rollover is anticipated by the electronics, then accidents will be prevented. Until recently, though, no automaker or federal safety body has actually quantified the effects of widespread stability control use. But details have now been released of a study which actually proves that traffic safety is enhanced by stability control systems.

Before wading into the details of this study, a recap on stability control might be worthwhile.

In recent years, stability control systems have appeared under a variety of names, according to the automaker’s branding policies. Basically, ESP (Mercedes-Benz), DSC (BMW), and StabilTrak (Cadillac) achieve similar aims, as do comparable systems offered by many other automakers. It’s an alphabetical minefield for car buyers, but well-informed sales people will always be able to explain how each version functions.

Electronic Stability Program
ESP holds cars on a steady course: During understeering (left) the front wheels turn outward; ESP automatically applies the brake to the left rear wheel. When the rear end breaks away during oversteering (right), ESP brakes the right front wheel. Source: Mercedes-Benz. Click image to enlarge

A typical stability control system uses sensors to constantly monitor individual wheel speed, steering angle and lateral acceleration. Also monitored on many systems is yaw, an aspect of aerospace technology automakers have learned from. All this information is gathered in by the computer, which determines whether or not the vehicle is headed in the direction the driver intends. If the car becomes unstable and begins to skid or spin, the computer applies brake pressure at one or more wheels – something no driver could ever do. The system also comes into play if a rollover is sensed as being imminent.

Mercedes-Benz has been tracking the effects of its ESP system on accident levels in Germany and has come up with some interesting figures. ESP has been standard on Mercedes-Benz products for five years or so and recent studies have indicated that there’s been a significant decrease in driver-related accidents in which control is lost after a skid and as a result, the vehicle leaves the road.

Experts at Mercedes say that if all automobiles were equipped with a stability system like ESP, 20,000 serious accidents a year could be prevented in Germany – accidents that result in injury or even death to 27,000 people. Multiply this to include the rest of Europe and then North America and Asia and the figures would be astonishing.

According to Mercedes-Benz, accidents involving its various models have been cut by 42 per cent between 1998/99 and 2002/03. Other brands using stability control systems have also seen accident rates drop, but Mercedes claims that its ESP has been responsible for the most dramatic improvements. It’s worth bearing in mind that the motoring scenario in Germany involves many roads with no speed restrictions where vehicles travelling at 200 km/h and more are commonplace. I would guess that a stability control system would have a lot more work to do bringing a vehicle under control at 220 km/h than it would at the 100 km/h speeds that are more common here.

According to Mercedes, driver-related accidents (the ones that are more effectively dealt with by stability control) are usually the most severe and in 2003, were responsible for some 43 per cent of all traffic fatalities and 20 percent of all injuries in Germany. Mercedes believes, and other automakers probably agree, that stability control programs are the key safety systems in today’s vehicles, along with seat belts and air bags.

One interesting aspect of electronic stability control that’s not usually considered is its ability to reduce the extent of injuries to vehicle occupants in an accident. Since systems like ESP stabilize the vehicle in a skid, the risk of side-on collisions with trees, hydro poles or other such objects is very much reduced. The vehicle is brought under control and stopped in a straight line, aided by the anti-lock brakes and brake force distribution, which is usually part of any stability control system. The German study also showed that passenger cars equipped with stability control roll over less frequently than vehicles without the system. Mercedes-Benz says that since stability control was standardized, vehicle rollovers involving its products have decreased by around 12 per cent.

Stability control has also had a positive effect in the US and Sweden, according to other research. The American Insurance Institute for Highway Safety has concluded that ESP and systems like it can reduce the number of fatal traffic accidents by some 34 per cent.

The best news of all about stability control programs is that they are “creeping downmarket” and becoming available on even lower-priced vehicles. As any observer of the consumer electronics industry knows, the more products sold, the cheaper the price and the same will apply to these highly sophisticated and complex stability control systems. They are certainly among the electronic miracles of our time, but in the years ahead, they are likely to become as commonplace as air bags and seatbelts. In the meantime, it’s an option worth buying if it’s available on any new vehicle that doesn’t have it as standard.

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