AAA tests highlight limitations of some emergency braking systems

Some buyers may be unaware that some systems focus on \'mitigation,\' reducing impact speed but not entirely avoiding collisions.

Tests conducted by AAA highlight the limitations of some automatic emergency braking (AEB) systems.

The organization warns that many drivers may be unaware of the differences between AEB systems offered by different automakers or even between different models of the same make. Some are designed to stop the vehicle and prevent crashes, while others aim to simply slow the vehicle to lessen crash severity.

"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 AAA automotive engineering director John Nielsen. "The reality is that today's systems vary greatly in performance, and many are not designed to stop a moving car."

Adding to the confusion, some systems designed to completely avoid collisions will not completely stop the vehicle from high speeds. In other cases, systems designed to slow the vehicle will bring it to a complete stop if approaching an obstacle at low speeds.

Overall, the AAA tests demonstrated the added value in the best AEB systems available in current vehicles. When pushed beyond the typical design limitations stated in owner's manuals and approaching a stopped vehicle at 45 mph, systems capable of preventing crashes reduced speeds by 74 percent and avoided crashes in 40 percent of the tests. Systems designed to lessen crash severity were only able to reduce vehicle speed by nine percent.

The tests echo the logic behind the Insurance Institute for Highway Safety's rating system for AEB technology. The IIHS approaches obstacles from 12 mph and 25 mph, giving top scores to vehicles that completely avoid collisions in both scenarios. The scores are then factored into the qualification criteria for Top Safety Pick awards.

The technology should become more widespread toward the end of the decade. A group of nearly two dozen automakers has voluntarily committed to making AEB a standard feature on all new cars by 2022.

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