A new study from the American Automobile Association (AAA) has found that rain can severely impair advanced driver-assistance systems (ADAS). Similar to how highway traffic slows to a crawl when there’s a sudden deluge, modern safety equipment can have real trouble performing when a drizzle becomes a downpour.
On Thursday, the motor club organization released findings from closed-course testing that appeared to indicate some assistance suites had real trouble seeing through bad weather. AAA reported that 33 percent of test vehicles equipped with automatic emergency braking traveling collided with a stopped car when exposed to simulated rainfall at 35 mph. The numbers for automatic lane-keeping was worse, with 69 percent drifting outside the lines. Considering the number of times the people writing for this website have anecdotally criticized ADAS for misbehaving in snow, sleet, rain, fog, or just from an automobile being a little too dirty, it’s hard not to feel a little vindicated.
But AAA never seems to be looking for validation. It’s been taking a sober look at advanced driving systems for years, often coming to the conclusion that the industry has released subpar technology onto the streets. This time was no different, with the outlet suggesting evaluating ADAS under pristine conditions ignores the realities of having to live with these systems 24/7.
“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.”
However, we’ve seen enough testing conducted beneath sunny skies where driving aids still allowed vehicles to repeatedly smack into simulated pedestrians to know that’s only part of the problem. AAA even conducted a few of those, with the results falling short of something we’d be willing to entrust our lives on. It’s actually kind of amazing that we’ve even allowed them to be installed into over 90 percent of modern automobiles (making them more expensive) when there’s really no regulatory framework for quality assurance and most objective testing has shown them to be somewhat unreliable even under the bluest skies.
Things just get sadder when you expose them to a low-light environment or moderate levels of precipitation. Meanwhile, there’s mounting evidence that relying on ADAS dulls the senses of the driver and can encourage dangerous levels of complacency behind the wheel. But you don’t even get anything out of that because current systems technically force you to interact as if you’re totally engaged even though the car is supposedly doing all the work.
The AAA study, which was conducted in cooperation with the Automobile Club of Southern California’s Automotive Research Center (ARC), simulated rain using a mount that sprayed vehicle sensing equipment and the windshield. Cars tended to have more trouble contending with more rain and/or higher speeds. At 25 mph, 17 percent of the test runs examining automatic emergency braking ended in a crash. At 35 mph, that number rose to 33 percent. However, things were reportedly better when the window was smeared with bug guts and grime.
During testing with a simulated dirty windshield (stamped with a concentration of bugs, dirt and water), minor differences were noted, however, performance was not negatively impacted. While AAA’s testing found that overall system performance was not affected, ADAS cameras can still be influenced by a dirty windshield. It is important drivers keep their windshields clean for their own visibility and to ensure their ADAS system camera is not obstructed.
Also, some systems may provide an alert or deactivate in extreme situations, however, the conditions AAA tested under provided no such alert or warning.
To simulate rainfall, AAA engineers designed a system using a reservoir to hold water, a high-pressure pump for a consistent flow of water and a precision injector nozzle to spray the windshield. This system was secured in the cargo area of the test vehicle and was connected to a nozzle positioned above the windshield so that the spray pattern covered the entire windshield. It should be noted that water sprayed by this system did not reach the pavement or interact with the test vehicle’s tires.
The outlet suggested that the best way to mitigate risk is not to trust these systems and follow the practices that make for an engaged, defensive driver. Knowing how the systems work on your own vehicle is also advisable and could help in making those unpredictable scenarios where ADAS goes blind or attempts to steer you off the road a little less mysterious.
“AAA recognizes these systems have the ability to lessen the chance of a crash and improve the overall safety of driving,” stated Brannon. “Fine-tuning their performance and providing drivers with a more consistent experience will go a long way in unlocking their true potential.”
While AAA’s emphasis on consumer advocacy makes me biased toward supporting them, I do have to point out a few shortcomings in the study. Testing was only limited to a handful of vehicles due to the researchers’ logistical limitations. But AAA and ARC attempted to mitigate this by sampling a variety of mainstream models from around the globe in the most popular body style. Vehicles included a 2020 Buick Enclave Avenir (with Automatic Emergency Braking and Lane Keep Assist), 2020 Hyundai Santa Fe (with Forward Collision-Avoidance Assist and Lane-Keeping Assist), 2020 Toyota RAV4 (with Pre-Collision System and Lane-Tracing Assist), and 2020 Volkswagen Tiguan (with Front-Assist and Lane-Assist).
If you’re interested in dodging the aggregate data and want to learn how each vehicle performed individually, we recommend you check out the complete study. The same goes if you have questions about how the testing was conducted or what hardware was used to tabulate the data because it’s quite comprehensive. AAA also has related studies focusing specifically on lane-keeping features, driving aids failing to see pedestrians, and the ways these systems can actually make it harder to drive safely.
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