By on October 15, 2021

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.

From AAA:

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.

[Image: AAA]

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27 Comments on “Rain or Shine: AAA Finds Out Advanced Driving Aids Still Suck...”

  • avatar

    I know that the camera for the automatic braking in my cars gets easily dazzled if I’m driving toward the sun and the sun is at a shallow angle. An example currently would be driving westward at about 16:45 in Minnesota. In that case the car provides a warning the system is off.

    I also get the warning that radar cruise doesn’t work under 20 mph. I wish there were an easier way to put regular cruise on in the cases where radar cruise is inactive. In my other Mazda, I could long-press the switch and change the mode of cruise control (standard or radar).

    • 0 avatar

      “ I wish there were an easier way to put regular cruise on in the cases where radar cruise is inactive.”

      Jeep does that.

      You have dedicated buttons for activating the regular cruise and radar cruise. You choose what system you want and then you use the same “resume, cancel, set+ and set-“ to adjust.

      • 0 avatar

        Usually you can’t activate cruise control of any sort until 25mph or above. Although some makes, such as Honda, let you set a minimum 25mph speed into the cruise control as long as your foot is off the brake pedal, even if the car is stationary, and in “brake hold” mode.

        Oddly, I had what I think was the first “false alarm” of one of the systems on my 2019 Accord Touring, but it was just a large leaf that happened to land on the left-front parking prox sensor as I was starting-off from a stop sign, which scared the bejeebers out of me! My last car falsed on a steel plate put on top of a street repair, but thankfully that was only an audible and visual warning, without auto-brake!

        As for the lane-keep assist in my Accord, it’s pretty good even with wet pavement and/or direct sunlight! The thing I wouldn’t trust is adaptive cruise linked solely to a camera, as in the case of the Subaru EyeSight system, or the HondaSensing suite found in the new Civic — the radar should back-up the camera for anything high-speed.

        • 0 avatar

          To be clear, I’m not generally trying to activate it at low speeds, but I get the idiot light. I’m sure there’s a way to turn the adaptive function off in the circumstances I do use it, but it’s buried in a menu somewhere. Tonight I was driving back from Duluth to St. Paul and had adaptive cruise control on – I paid for it and I’m darn well going to use it – and was irritated more by the left squatters when the car in front was varying wildly in speed.

          I have had the traffic stop-n-go function on a few times (it’s built in to the adaptive cruise), but am usually too unnerved to really use it much.

        • 0 avatar

          In my Subaru, cruise control goes down to 0 mph, and it’s great because then it handles stop and go traffic. You really don’t have to do anything — turn on the smart cruise and the auto steering and other than twitching the wheel every 30 seconds to shut up the nanny, the car does it all.

      • 0 avatar

        So do Toyota and Subaru (the brands we have right now). Getting to the regular cruise is not completely obvious in either one though.

  • avatar
    Arthur Dailey

    Auto lane keeping, auto braking I do not trust/like. I also dislike adaptive cruise but realize that others do. But then I also dislike back-up cameras. And I still ‘pump the brakes’ when stopping on loose snow, etc. And I detest the ‘automatic engine red light stop/start’ function.

    However traction control, stability control and blind spot monitoring are ‘nannies’ that I know consider to be ‘must haves’. And yes I use ‘cruise control’ on relatively empty highways, in good weather, on a regular basis.

  • avatar

    ?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.”

    Well, unlike Tesla, most manufacturers unambiguously market them as assistance aids, and *not* something you should “entrust our lives on.”

    I have adaptive cruise, lane-keeping, etc., on my CR-V, and I use them for most highway driving. They are useful in taking over the fine-tuning tasks of precise lane-keeping and following-distance maintenance, leaving me to pay more attention to the driving tasks it doesn’t even pretend to attempt (like spotting an 18-wheeler merging into my lane a 1/4-mile down the road.)

    With the exception of Teslas, anybody that’s ever driven with any of these systems even once would be nuts to even attempt to use them like some sort of auto-driving. They aren’t meant to take over driving entirely, aren’t sold that way, and don’t even vaguely approach that level of performance in a way that would lull anybody with a half-dozen cells to rub together into a false sense of security.

  • avatar

    So, I was right all this time that these nannies !will! kill you. In Russia they even had a saying for this – 9 nannies and a child with a poked eye

    • 0 avatar

      I’ve seen dash cam compilations from Russia. Y’all need actual driving lessons, every electronic nanny available, and a mandatory top speed of 20.

      • 0 avatar

        The only difference to US is that in US not many have dash cams. Hey, if I did not work in the building that sits 20 feet below and next to the curve of the highway exit ramp, I wouldn’t know how many cars and trucks fly off that ramp. And it is always the same. First you hear crazy sounds, braking, grinding. Then tumbling. At that moment you know that you need to come out and see, if you can pull a person out of the vehicle that tumbled down into the fence. And call the 911

  • avatar
    Tele Vision

    This Just In: Driving Requires Driving.

    I haven’t used cruise control since 1989. Fact. I don’t even know how to activate it on any of my current vehicles.

    Actually driving a car or truck provides many instances of seeing people looking at their devices at speed, though – which is what we’re headed for if we don’t stop optioning radar-cruise and auto-braking and auto-lane-keeping and similar dross in new cars.

    You won’t do so, though, so I’m still buying older, better cars with none of that expensive and falsely-insulating tech on them. I may even go further back and install carburetors on my fun cars.

  • avatar

    My Venza’s radar cruise control is useless except in gridlocked crawl and go traffic where it is brilliant. I have always picked a speed while driving on the highway. If I close in on a car, then its time for the left lane and a pass. Radar cruise backs off and without me realizing, then I’m going five to ten less than my select speed. It also has failed me when I move to pass a truck on a left hand curve, the radar cruise sees the semi directly ahead (in his lane of course) and backs off. The “cornering asisst” is off. The lane tracker literally makes the steering wheel fight me, it is turned off. I forget the whole list but less than half of all that automated assistant crapis turned off. No thanks. Some of the features are good, but most are worthless.

  • avatar

    The “AAA B Roll video” above demonstrates another potential problem with Automatic Emergency Braking.

    View the first ‘successful’ stop (shown twice from different angles). In the real world, if you (computer or otherwise) stop the vehicle like that (fairly last-minute, fairly aggressive braking, stopping short of the vehicle ahead, full ‘hard’ stop with no brake let-off), you will very likely have a third vehicle (purely human-driven or otherwise) plowing into the back of the second vehicle (Hyundai? in the video). And potentially the same thing happening farther back in a (small or large) chain of collisions.

    Because typical following distances (fairly aggressive human, or adaptive cruise set at minimum following distance) and reaction times (distractions for a human, processing time for a computer) aren’t going to allow for close-to-maximum braking events in a line of closely-spaced vehicles without some vehicles making contact. Assume a line of ~6 vehicles closely following each other for illustration (or simulation) purposes.

    My understanding is that at least some vehicles with Automatic Emergency Braking are able to look two vehicles ahead (for example). Which should help (some). The other thing that would help is the occasional driver maintaining a larger gap to the vehicles ahead (call her a ‘moderator’ if you’ve been watching fission videos like I have), with accelerator let-off and smoother braking when approaching the 6 stopped (with some maybe crashed now) vehicles.

    (‘Contact’ is likely to result in property damage and possibly injuries.)

    A) In the real world there are more than two vehicles on the roadway. For the foreseeable future, it will be a mix of automated, augmented and ‘human-only’ vehicles. The interactions matter, and should be factored into testing.
    B) Experienced/proficient drivers behave differently than inexperienced/inept drivers. Model the safety systems on the better drivers.

  • avatar


    AI was recognized to be a dead end by the 60s. Among literates, it died with Flash Gordon and flying cars.

  • avatar

    All these driver aids do is make up for a lack of driving skills. They are not “safety” devices. They are like the bumpers at a bowling alley. You can still miss the pins despite their use.

    That being said in 100k miles, I’ve never had an issue with the radar cruse in my vehicle. Rain, sun, fog, snow it works great. I’m not a Tesla mouth breather and will read a book or sleep when it is activated but for long hauls or stop and go traffic it’s great.

    • 0 avatar
      C5 is Alive

      The “bumpers” analogy is a good one. I just got home from a 17-hour round trip and I found adaptive cruise, active lane keeping, et al to be rather useful tools to ASSIST with driving, but of course none of them can REPLACE the driver at any step in the process.

      • 0 avatar

        The auto stop-‘n-go on my Accord’s adaptive cruise is a Godsend indeed!

        As Arthur mentioned, the auto start-stop for the engine is an entirely different thing! I drove a 2021 Accord 1.5T with it, and while it wasn’t as intrusive as some other makes seem to be just by all the racket they make when grinding back to life at intersections I pass on my walk from my parking lot to the office, it still wasn’t as smooth as the same system found on hybrid vehicles! The vehicle owner should be able to deactivate the system and have the status retained between ignition cycles without a warning light or nag message in the information center or infotainment!

  • avatar

    Really? Who’d have thought!

    First, let’s get the language clear – if you cannot shut it off for good, those are not “aids”.
    I’m driving my manual Volvo v70 ’98 until it dies or I do.

  • avatar

    The issue is that 40,000 people die every year in the US from car crashes. Do these systems help reduce that, can they be improved? I think the answer to both are yes.

    My experience with my KIA e-Niro, is that the systems help reduce fatigue and allow my to focus on driving without the concerns of slowing/speeding, minor decreases in speed of traffic ahead etc.. After hours at the wheel, I am relaxed and , if not ready for more, very much capable of more.

  • avatar

    So these systems don’t necessarily work all the time. Well, color me shocked – SHOCKED!

    My new car has automated emergency braking, which has never kicked in but did warn me once. I’d be foolish to rely on it, though.

  • avatar
    Gabe Ets-Hokin

    Hey! Here’s a wacky idea: let’s all drive our own f-ing cars and then focus billions of dollars and the minds of the greatest engineers and programers in the world to solving actual problems.

    • 0 avatar

      “and then focus billions of dollars and the minds of the greatest engineers and programers in the world to solving actual problems.”

      The technology that is being developed for autonomous vehicles does have applications beyond the automotive world. I’m developing a new generation of AI that is being simultaneously targeted towards autonomous vehicle navigation and medical uses. In fact, any of the other AI technologies, hardware and software, have multiple applications in automotive, medical, and security applications. You could probably rip auto-pilot hardware from a Tesla, and with retraining and replacement of the cameras with a medical image stream, perform tumor search or something similar. It’s all related and basically the same.

      One direct beneficiary of the autonomous vehicle tech is the military. That’s where we got our start. In DARPA challenges. The military definitely has their uses for AV technology.

    • 0 avatar
      Matt Posky

      This is a good idea.

  • avatar

    I drive our freeway in winter, in my RWD car, and the ditch is full of S/CUVs with ABS and skid control and steering assist etc. My wife’s friends think I’m a monster for not buying her an SUV, neither of us has been in the ditch in winter with our car.

  • avatar

    Let us not forget the most advanced driving aid of all, Android Auto, which disables half of its functions at the precise moment when you need them most (ie: while driving a car) thus compelling you to yank the USB cord out of your phone in a fit of rage, pounding away furiously at the screen while balancing it on your knee.

    If Hell has an engineering department, it is surely located at Google headquarters.

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