Driver Assistance Systems Defeated By Rain

Technology / Comments

The AAA says rain has a negative effect on automatic braking and lane-keep assist.

The American Automobile Association (AAA) recently conducted a new study to see how advanced safety features perform in bad weather. To test their performance, the AAA used a closed course and simulated moderate to heavy rainfall. It also simulated other real-world conditions, like dirt and bugs.

The results are shocking considering that a new generation of drivers has more confidence in these systems, not knowing anything else but Level 2 autonomous vehicles. These new safety systems can actually have the opposite effect, creating dangerous distracted drivers.

Vehicles equipped with automatic emergency braking were driven down a road at 35 mph in the aforementioned conditions, colliding with an inflatable Fiesta 33% of the time. Lane-keep assist has an even more challenging time, with vehicles departing their lanes 69% of the time.

The AAA states that these safety features are usually tested in ideal operating conditions and that it believes real-world situations need to be incorporated as well. Considering the result of this study, we're inclined to agree. We also can't help but be reminded of the AAA's studies conducted in 2019 and 2014.

American Automobile Association / Brion Lee
American Automobile Association / Brion Lee
American Automobile Association / Brion Lee

"Vehicle safety systems rely on sensors and cameras to see road markings, other cars, pedestrians, and roadway obstacles. So naturally, they are more vulnerable to environmental factors like rain," said Greg Brannon, AAA's director of automotive engineering and industry relations. "The reality is people aren't always driving around in perfect, sunny weather, so we must expand testing and take into consideration things people actually contend with in their day-to-day driving."

A look at the aggregate results gives even more insight. The automatic emergency braking was tested at 17 mph, in which case the cars only crashed in 17% of test runs. At 35 mph, the figure essentially doubled to 33%.

"AAA recognizes these systems have the ability to lessen the chance of a crash and improve the overall safety of driving," continued Brannon. "Fine-tuning their performance and providing drivers with a more consistent experience will go a long way in unlocking their true potential."

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The AAA's findings don't correlate with a study conducted by the Insurance Institute for Highway Safety (IIHS) and Cadillac, claiming that automatic braking could cut crashes in half. Those tests were not completed in the rain, showing how much of a difference it can have.

The AAA also simulated a dirty windscreen with squashed bugs, dirt, and rain. The performance of the safety systems was not affected. Still, the AAA recommends keeping your windshield clear to ensure the safety system's cameras are not obstructed.

In case you were wondering how you simulate rainfall, the solution is quite simple and elegant. The AAA engineers used a reservoir, a high-pressure pump, and a precision injector nozzle. The larger components were stored in the trunk, and the nozzle was placed in the correct position to spray the entire windscreen.

The AAA did not name specific models, but the image attached to the press release shows a Hyundai Santa Fe. We're sure more cars were tested, but that information is not available. It would be interesting to see how a Level 3 car copes with these conditions.

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