New technologies raise the bar on highway safety

Stability control, air curtains are more available

By Christopher Jensen, Globe Correspondent  |  February 18, 2007

It's not uncommon for car shoppers to dither over color, options, or price. But safety specialists recommend two new safety technologies as must buys: electronic stability control and air curtains.

Electronic stability control applies brakes to individual wheels if the system senses the car is veering out of control. Air curtains are air bags -- sometimes called side curtain air bags -- that drop from the car ceiling to provide crucial head protection in deadly side-impact crashes.

Studies have concluded that wider deployment of each can dramatically reduce accidents and/or fatalities. Both are standards in some models, but cost as much as $800 each when available as an option.

Electronic stability control, according to the National Highway Traffic Safety Administration, is the biggest lifesaver since seat belts. It's so effective that the NHTSA estimates 4,200 to 5,400 of the 10,000 deaths caused each year in rollover accidents could be prevented if it were on all vehicles.

The system uses sensors and a computer to tell if the front or rear of the vehicle is sliding in a direction other than where the driver is steering. Then working with the anti lock brake system, the computer applies brakes on individual wheels to arrest the skid or correct the direction of the car. That's different than just using the antilock brakes alone, where all four brakes would be pumped at the same time.

Studies in Japan, Europe, and the United States determined that electronic stability control saves lives, especially in single-vehicle accidents where the driver loses control. One 2006 analysis by the Insurance Institute for Highway Safety found that electronic stability control reduced single-vehicle fatal crashes, which are often caused by the driver losing control, by 56 percent.

The NHTSA is considering requiring automakers to install electronic stability control on all vehicles no later than Sept. 2011 for the 2012 model year. A decision is expected before spring.

Electronic stability control is thought to be particularly important for tall vehicles, such as SUVs, pickups, and minivans, because their higher center of gravity makes them more vulnerable to a rollover. The danger is that when such vehicles begin to slide sideways it is easy for them to be "tripped" by a curb or soft ground and roll over.

Electronic stability control can help the driver regain control of the vehicle before it can be tripped, said David S. Zuby, the senior vice president for vehicle research at the Insurance Institute. A University of Michigan study last year found electronic stability control reduced the chance of an SUV being in a fatal rollover by 73 percent.

Electronic stability control is not foolproof. It may not help, for example, if a road is so icy tires have no grip. Moreover, safety researchers are analyzing whether some stability systems work better than others.

Less a third of 2006 model year vehicles had electronic stability control, but that figure is expected to jump to 71 percent by 2011 model year -- even without a federal mandate, according to the NHTSA.

Mercedes-Benz introduced electronic stability control in 1995 and it has since gone mass market. For example, it is standard on the 2007 Hyundai Sonata, which has a starting price around $18,000. As an option, electronic stability control is often $400 to $800, although a few automakers make it more expensive by bundling it in packages that include non safety items.

Automakers also have their own brand names for electronic stability control: StabiliTrak at General Motors; Advance Trac at Ford; and Vehicle Stability Assist at Honda.

The numbers for side curtains are also compelling. The head protection from the bag can reduce the chance of being killed in a side-impact crash by about 45 percent, the insurance institute found in a 2003 study. Similarly, the federal highway safety agency estimated that if all vehicles had side air bags as many as 1,000 lives a year would be saved from side-impact crashes.

"One of the major reasons people get hurt and killed in side-impact crashes is that they have severe head injuries," said Zuby.

One danger is being hit broadside by an SUV or pickup, which have high-riding fronts that strike a car higher and closer to the heads of its occupants.

Air curtains are low-pressure air bags that are mounted inside the roof. In a side-impact crash they deploy downward to cover the front and rear side windows, helping to shield the head.

An alternative is a seat-mounted air bag, but in most cases these are only for the front seats. In addition, not all seat-mounted bags provide head protection. Some provide only chest protection. Some side-impact safety packages combine air curtains and the front, seat-mounted chest bags.

Air curtains are increasingly a standard offering -- even the Honda Fit, priced around $14,000, has them. As an option automakers tend to price them between $600 and $800.

Zuby recommends car buyers who want to do a "thorough job" of shopping for a safe car should consult crash-test ratings.