Anti-lock brakes can provide more stable braking in wet or slippery conditions.

Saturn

But the Michigan woman didn't always feel this way. In fact, when she bought her Saturn she didn't care that it had ABS. The system was new to Heard and she wasn't sure how it worked.

However, a few months later Heard learned firsthand how ABS can help drivers maintain control while braking on the road. She was driving in the dark on a six-lane Michigan expressway.

"I happened to be in the middle, between two semis," she said, when a big, metal-banded wood crate fell onto the road ahead. Traveling at 70 miles per hour and with no place to maneuver, she slammed on the brake pedal, and then feared she would collide with one of the burly semis beside her.

To her amazement, "I maintained control of the car; I was able to keep the steering wheel straight," Heard said. The metal-bound crate smacked into her driver door with force, leaving shards of wood embedded in the Saturn's polymer body panels. But Heard's car never touched either semi.

Uninjured, Heard became a driving testimonial for ABS.

Started in the Late 1970s

ABS has been available on U.S. vehicles since 1978. Mercedes-Benz was the first to install anti-lock brakes on production cars. By 1986, Cadillac began adding it to its high-end luxury cars.

The system uses onboard computers linked to individual wheel sensors to automatically "pump the brakes" at a rate faster and more precise than human reflexes can duplicate. Anti-lock brakes also apply pressure selectively, by sensing which wheels are close to lockup at any instant and then lowering braking pressure to those wheels until they rotate properly. ABS works only in hard panic stops and does not engage in normal braking situations.

Like power brakes, which merely boost force in otherwise conventional drum- or disc-braking mechanisms, anti-lock brakes add another layer of control; they are not a new friction-creating technology for slowing a vehicle's wheels.

Issues

ABS does not necessarily provide a shorter stopping distance. It won't stop you on a dime, either. Its primary advantage: It allows a driver to continue to maintain steering control and avoid skidding while stopping.

Still, there have been issues with ABS. Safety officials expected to see immediate results in real-world crash data as ABS became more prevalent on new vehicles.

But at least two studies in the 1990s—one performed by the National Highway Traffic Safety Administration (NHTSA) and another by the Insurance Institute for Highway Safety—showed little overall difference in crash rates between cars with ABS and those without them.

A later NHTSA study, which included a wider sample of vehicles and was released in 2000, stated ABS "appears to be beneficial in preventing pedestrian crashes, rollovers, run-off-road crashes and frontal crashes with another moving vehicle."

And in 2002, General Motors Corp. officials said they'd no longer put ABS as a standard feature on most of its 58 vehicles, starting in the 2003 model year. ABS would be offered as an option, instead. The company said the move was intended to keep it competitive in price with other automakers' vehicles. GM added that its Cadillac, Saab and Corvette vehicles would continue with standard ABS and would not be part of the change.

Must Use ABS Correctly

Safety advocates remind that it's important that drivers know how to use ABS properly. Otherwise, they won't get the benefit from the technology. "Anti-lock brakes are an unfamiliar technology to many people," NHTSA spokesman Tim Hurd said.

Drivers who have been trained to brake gently on slippery roads and to pump brakes to avoid a skid must unlearn these techniques, which are often ingrained, safety officials said.

How to Use ABS

  • "Stomp and steer," Hurd said. Don't treat ABS gingerly as you would ordinary brakes. Instead of pumping, press hard on the pedal without letting up. Any pulsing you feel or noise you hear is the ABS doing its job.
  • Remember that anti-lock brakes are chiefly designed to provide steerability. So don't wrench the wheel and freeze up. Focus on where you want your car to go and steer there as the ABS does its job to keep the car stable, just as Heard did in Michigan. "If you look at the obstacle you're wanting to avoid, chances are you're going to hit it; it's how the brain works," said Jim Gill, spokesman for Continental Teves, a manufacturer of ABS.
  • Make sure to practice how to use your ABS before you get into an emergency. Fred Heiler, Mercedes spokesman, encouraged drivers to "find an empty parking lot" to rehearse panic stopping. This also could help the driver get used to any pulsing or noise that might be associated with ABS.

What to Look for When Buying a New Vehicle

  • Check to see if ABS is standard equipment or an optional feature. Many manufacturers, including Volvo and Mercedes-Benz, have made ABS standard equipment.
  • If ABS is optional, you might want to weigh the extra cost against your probable use of ABS. Remember, ABS works to prevent skids, which generally occur at high speeds and on wet or icy roads. They do not activate during normal, everyday stopping. However, if used correctly in an emergency they can stop your car more safely than conventional brakes can.
  • On cars, ABS is connected to all four wheels. On trucks and vans, ABS may only involve the rear wheels.
  • Changing tire sizes may affect ABS performance because a different size tire will rotate at a different speed. This will affect the operation of the wheel sensors. For more information, consult the owner's manual for the vehicle or find out from the manufacturer's customer service department.

What to Look for When Buying a Used Vehicle

  • Remember that the function of ABS is to help a driver with panic braking in certain situations; the brakes themselves are the same as on a conventional vehicle. Whether or not you are shopping for a vehicle with anti-lock brakes, look for brakes in good condition, ones that have been recently serviced or replaced, depending on the model's maintenance requirements and individual history.
  • Disc brakes—which are less prone to fade—on all four wheels are best, although many vehicles feature disc brakes only on the front wheels and rely on older-style drum brakes in the rear.
  • Avoid aftermarket "add-on" anti-lock brakes—there aren't any that are effective and some are outright consumer rip-offs. Only electronic anti-lock brake systems are effective at stopping vehicles in the way the systems are designed. Such systems are only available through factory installation.

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