AAA tests: Not all self-braking cars designed to stop

WASHINGTON — New test results from AAA reveal that automatic emergency braking systems vary widely in their ability to stop a moving car.

The tests reveal automatic emergency braking systems capable of preventing crashes reduced vehicle speeds by twice that of those designed to lessen severity. All the systems tested by AAA are designed to apply the brakes when a driver fails to engage.

Although a reduction in speed might be a benefit to drivers, AAA said that automatic braking systems are not all designed to prevent collisions.

Rear-end collisions, which automatic emergency braking systems are designed to mitigate, result in nearly 2,000 fatalities and more than 500,000 injuries annually, according to the National Highway Traffic Safety Administration.

Ten percent of new vehicles have automatic emergency braking as standard equipment, and more than half of new vehicles offer the feature as an option.

“In an emergency situation, the technology has the potential to prevent a crash or reduce the impact speed of a crash. While it is designed to mitigate the severity of an impact, the driver remains responsible for the vehicle at all times,” said John Townsend, AAA Mid-Atlantic’s manager of public and government affairs. “Some systems are designed to mitigate crash severity by reducing vehicle speed, while others are designed to avoid a crash altogether when possible. While automatic emergency braking systems are designed to reduce vehicle crashes, the technology is not fail-safe.”

AAA also evaluated five, 2016 model-year vehicles equipped with automatic emergency braking systems to gauge performance during real-world conditions drivers that were likely to face.

“AAA found that two-thirds of Americans familiar with the technology believe that automatic emergency braking systems are designed to avoid crashes without driver intervention,” said John Nielsen, AAA’s managing director of automotive engineering and repair. “The reality is that today’s systems vary greatly in performance, and many are not designed to stop a moving car.”

After more than 70 trials, tests revealed:

  • In overall speed reduction, the systems designed to prevent crashes reduced vehicle speeds by twice that of systems that are designed to only lessen crash severity (79 percent speed reduction vs. 40 percent speed reduction).
  • With speed differentials of under 30 mph, systems designed to prevent crashes successfully avoided collisions in 60 percent of test scenarios.
  • Surprisingly, the systems designed to only lessen crash severity were able to completely avoid crashes in nearly one-third (33 percent) of test scenarios.
  • When pushed beyond stated system limitations and proposed federal requirements, the variation among systems became more pronounced.
  • When traveling at 45 mph and approaching a static vehicle, the systems designed to prevent crashes reduced speeds by 74 percent overall and avoided crashes in 40 percent of scenarios.

“Automatic emergency braking systems have the potential to drastically reduce the risk of injury from a crash,” said Megan McKernan, manager of the Automobile Club of Southern California’s Automotive Research Center. “When traveling at 30 mph, a speed reduction of just 10 mph can reduce the energy of crash impact by more than 50 percent.”

In addition to the independent testing, AAA surveyed U.S. drivers to understand consumer purchase habits and trust of automatic emergency braking systems. Results reveal:

  • 9 percent of U.S. drivers currently have automatic emergency braking on their vehicle.
  • Nearly 40 percent of U.S. drivers want automatic emergency braking on their next vehicle.
  • Men are more likely to want an automatic emergency braking system in their next vehicle (42 percent) than female drivers (35 percent).
  • Two out of five U.S. drivers trust automatic emergency braking to work.
  • Drivers who currently own a vehicle equipped with automatic emergency braking system are more likely to trust it to work (71 percent) compared to drivers that have not experienced the technology (41 percent).

“If I were shopping for a vehicle, I would definitely consider looking for one that in the owner’s manual says that it will strive to avoid a collision,” said Greg Brannon, director of automotive engineering and industry relations for AAA.

AAA tested a Volvo XC 90, Subaru Legacy, Lincoln MKX, Honda Civic and Volkswagen Passat from the 2016 model year to get a “cross section of the technology available today,” according to Brannon.

He said the Volvo, the Subaru, and the Lincoln all had owner’s manuals clearly stating the vehicle would try to avoid or mitigate a collision, while the Honda and VW owner’s manuals claimed only mitigation capabilities.

Ratings for an individual vehicle’s crash avoidance system are also available from the Insurance Institute for Highway Safety. Vehicles that are able to reduce speeds with automatic braking get an “advanced” rating for front crash prevention. Vehicles that can avoid crashes or substantially reduce speeds get a “superior” rating.

“We’ve got a lot of vehicles now that we’re giving ‘superior’ ratings to,” said Adrian Lund, president of the IIHS. He said although there are differences in how the systems perform, “we’ve seen big benefits from even just the basic system — the forward collision warning.”

The forward collision warning only alerts the driver about an impending crash and does not automatically apply the brakes.

The IIHS said forward collision warning systems are reducing front-into-rear crashes reported to police by 27 percent. However more advanced systems that can automatically brake are cutting rear-end crashes by 50 percent.

For its potential to reduce crash severity, 22 automakers representing 99 percent of vehicle sales have committed to making automatic emergency braking systems standard on all new vehicles by 2022. The U.S. Department of Transportation said this voluntary agreement will make the safety feature available on new cars up to three years sooner than could be achieved through the formal regulatory process.

WTOP’s John Aaron contributed to this report. 

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