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Pre-Collision Braking System

9K views 42 replies 17 participants last post by  Dannieboixdd 
#1 ·
I've driven ~43500 miles in my Ascent over the last 3+ years and haven't had many quirks with EyeSight. However, over this past weekend the same new behavior happened to me twice.

The first instance was Saturday while driving about 40mph down a road which I travel often, single lane in each direction, no oncoming traffic, I received the red flashing LED Pre-Collision warning on the HUD as I approached a curve to the left. The only obstacle in view was a yellow left arrow sign and a mailbox. The only factors I can assume contributed to the warning were the road being slightly wet from a light rain and few markings on the road in that location. The emergency braking did not activate.

The second instance was an offramp from the interstate that splits into 2 lanes then curves to the right. I was in the left lane and there was a guardrail in front of me with those same yellow turn signs. Again it had recently rained, traveling about 40mph, and I received the warning but no emergency braking.

Here’s a link to the videos from my dashcam
 
#2 ·
That's interesting. I think I remember only one or two false positives in ours. Both times, I did not get the emergency braking, but did get the flashing red LEDs. As I recall, those were also on roads with sharp curves and that behavior hasn't recurred. It must think it sees something in these types of scenarios, but I haven't been able to figure out what it is.
 
#6 ·
^ I've experienced both what @xydadx3 / @hokiefyd and @justmatt reported.

I believe that the latter is what is mentioned in pages 47-49 of the MY21 EyeSight Owner's Manual - https://cdn.subarunet.com/stis/doc/ownerManual/MSA5M2126A_STIS.pdf , where EyeSight doesn't "see" that second vehicle (either the one that's cut-in/out or the one that remains).

With the former, I think it has to do with how fast the vehicle thinks you're coming to/towards that seeming obstruction: that it's a perceived-stoppage vs. rate-of-change kind of deal.

There's definitely some interesting ghosts in the machine. My daughter and I have gotten to the point that we can almost always predict what the system will do, based on my driving inputs.

And it's that last that's why the cautionary statement @justmatt ended with in his last post above is so important.

No doubt about it, there's definitely times in my 3 years with the Ascent that EyeSight as well as the other safety systems have saved me from "pucker moments," but there's definitely also been more than a few times where the same systems have made some rather questionable calls that, had it not been for having RTMFM, there might have been some interesting outcomes, too (i.e. the vehicle following mine rear-ending me).
 
#7 ·
First, I'd try cleaning the inside of your windshield. It sometimes does things like that when signs or lights reflect back and create glare spots on the windshield.

Failing that, on turns, if one waits a little bit to initiate the turn, Eyesight tends to think you're going to drive into something. Could it have been that?
 
#8 ·
Judging by the replay it looks like I hadn’t yet gotten to the point in the road where I would’ve started turning. Maybe that contributed if it hadn’t locked onto the lane markings to see the road curving?
I do need to clean my windshield inside and out. While doing so I’m curious how the eyesight cameras are holding up or if they’re getting dirty. Since the manual tells us not to clean the lens covers and to cover them when cleaning, is there a way for them to be properly cleaned at some point?
 
#13 ·
^ I'm tempted to say (empirically, as I have no objective data to speak of) that EyeSight is more robust than we give it credit for.

I honestly can't imagine every EyeSight-equipped Subaru owner out there being nearly as fastidious as many of us who are on the Forums or in FB Groups are - we are by-definition a self-selecting dataset of, well, at least hobbyists, if not outright enthusiasts.

I mean, for all the folks who never take the time to RTMFM, we've also gotta take into account the entry-level-job interior cleaners at the typical wash-and-go..... 😅
 
#15 ·
Yep. I've gotten the warning on a number of roads with sharp bends that have large arrow signs at the bend. To Eyesight, it looks like I'm heading straight for an obstacle, until I start to turn. Another case is where I'm following a car and it slows and turns off the road. I know it'll be clear by time I get there but Eyesight doesn't register that it's leaving the path in front of me. Yet another is when I'm stopped at a 4 way stop, a vehicle is crossing in front of me, and I start to accelerate before it's totally past. And there's pulling too quickly into a parking spot or garage with a barrier, bush or wall at the end.
 
#17 ·
This is the part that gets me - the steering wheel is connected to the headlights, and the headlights will "bend" to illuminate the direction of travel. Why didn't this user story make it over to the Eyesight engineers, meaning, when the car is travelling around a moderate bend, "look" in the direction of travel, i.e. if the front wheels are pointed 5 degrees left, look 5 degrees left for obstacles.
 
#21 ·
I'm pretty sure Eyesight understands turns and lane markers when following a vehicle. I've had it successfully follow vehicles around the curves on our parkways on Long Island pretty regularly.
 
#22 ·
The second instance was an offramp from the interstate that splits into 2 lanes then curves to the right. I was in the left lane and there was a guardrail in front of me with those same yellow turn signs. Again it had recently rained, traveling about 40mph, and I received the warning but no emergency braking.
I've had exactly the same experience. Mountain road, in a curve, at night with light rain. I'm assuming that EyeSight picked up the refection from the series of yellow caution curve arrow signs. Definitely caught me off guard but like you, the auto braking system did not activate. However, the pre-collision braking system has given me a serious scare a few times while using ACC and a few times in normal traffic. I've had it over react and brake hard when the target car changed lanes and the new target is slowing down on the brakes. EyeSight immediately picked up the brake lights and the speed difference and "AGGRESSIVELY" applied the brakes taking both me and the driver of the car behind me by surprise. I'm concerned that this could actually cause an accident rather than prevent one.
The other much more annoying times the pre-collision braking activates is heavy traffic on surface streets at 45 mph or less. The car in front of you brakes abruptly to turn right so as not to slow traffic and you can clearly see that the car will complete the turn and clear the way without risk of a collision and the system activates. Can be interesting if you are already on the gas to accelerate back to the posted speed limit. The brakes came on so hard once the front tires actually chirped.
Don't get me wrong, the system absolutely works as advertised albeit almost too good at times.
 
#23 ·
I've driven ~43500 miles in my Ascent over the last 3+ years and haven't had many quirks with EyeSight. However, over this past weekend the same new behavior happened to me twice.

The first instance was Saturday while driving about 40mph down a road which I travel often, single lane in each direction, no oncoming traffic, I received the red flashing LED Pre-Collision warning on the HUD as I approached a curve to the left. The only obstacle in view was a yellow left arrow sign and a mailbox. The only factors I can assume contributed to the warning were the road being slightly wet from a light rain and few markings on the road in that location. The emergency braking did not activate.

The second instance was an offramp from the interstate that splits into 2 lanes then curves to the right. I was in the left lane and there was a guardrail in front of me with those same yellow turn signs. Again it had recently rained, traveling about 40mph, and I received the warning but no emergency braking.

Here’s a link to the videos from my dashcam
It happens to me on a 130° turn on my way to work every day. I have a 2021 Ascent Touring. Eyesight system is intrusive.
 
#32 ·
So I traveled the same road as the first instance, but no rain this time. It was twilight so my headlights were more visible but those were the only differences I can think of.
I even waited until the last moment to turn the wheel at the curve but I never got the warning this time 🤔
 
#33 ·
So I traveled the same road as the first instance, but no rain this time. It was twilight so my headlights were more visible but those were the only differences I can think of.
I even waited until the last moment to turn the wheel at the curve but I never got the warning this time 🤔
It would be good to know what the possible EyeSight triggers are so we can determine a non-issue versus a potential system problem that should be reported. I doubt I'll get a good answer from my dealer but I'll at least ask about this when I take it in for the next service.
 
#35 ·
I have the pre-collision warning lights/beeps come on about once or twice a week on this one sharp curve I drive a few times daily. Most of the times it's fine, but about 1 or 2 out of 10 times it will go off like it thinks I'm going to keep going straight. I assume that different lighting at different times of day, or cloudy/rainy vs sunny must factor into it getting fooled occasionally but not the majority of the time. (either that or it's just a moody little beast :))
 
#40 ·
I've found that a slight depress of the brake pedal (not braking) makes eyesight more forgiving. For this curve also adjusting my approach angle and not being at 0degree steering angle result in almost never warning any more.
Now I’m curious. I’ll have to remember to bring up the menu to see the steering angle on that curve. First I want to try to replicate the warning, then try to defeat it with steering/brake input.
 
#39 ·
^ That's in large part why I posed my question to @TheRaven , above.

I have noticed that slight inputs in throttle/braking and/or steering sometimes affects the EyeSight decision on whether or not to shout at me that my passenger and I are all doomed.... :p :ROFLMAO:
 
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#41 ·
I have one of these "curves", part of a freeway offramp.

I've found that a slight depress of the brake pedal (not braking) makes eyesight more forgiving. For this curve also adjusting my approach angle and not being at 0degree steering angle result in almost never warning any more.
^ That's in large part why I posed my question to @TheRaven , above.

I have noticed that slight inputs in throttle/braking and/or steering sometimes affects the EyeSight decision on whether or not to shout at me that my passenger and I are all doomed.... :p :ROFLMAO:
Wanted to add....

I think there are certain inputs which cause the corresponding part of the safety suite to understand that "driver is attentive and has control," and allows for more leeway before intervention.

For example, in reverse, the RAB will sound impending doom all day long, but as long as you're under 1 or 2 MPH (I've found that there's a variance, which I believe to be a lag in instrumentation, rather than actual speed difference) you can literally run over/through that obstacle. The same when going forward - tromp the throttle to indicate that you've seen the vehicle in front of you has indeed already cleared your lane, and forward collision mitigation will release the hounds.

I've come to think of these actions that I as the driver must take to be akin to a "Hang on, Chwie!" or "Better tense up, Legolas," friendly heads-up to the safety systems, to let them know that you've got it, and that it's on you...............

Boat Water Watercraft Cloud Vehicle
 
#43 ·
My eyesight paid for itself (before it became standard in 2016) while taking wife in labor to the hospital. NYC traffic sucks even on highways... turned my head for 3sec to check on her which in traffic (slow slow crawl). I didn't notice cars in front had slammed on their brakes. Needless to say, eyesight saved me $$$ and having to deliver on the highway... It was my fault either way for turning my head, but the experience with eyesight has been phenomenal.
 
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