Trying to learn why I get Phantom Braking (video)

[ElectricIAC]

It's one thing to have a warning that says it's "beta code," and it's another to have a huge warning across the screen saying, "Hey, this software is so bad right now that it's a known bug that it will slam on the brakes when you least expect it, so you're probably going to get rear ended, and we ain't going to pay for no stinking damages or funerals."

I feel this is how the SC’s can get away with saying “Oh, that’s normal. My car does it too”

 

[PianoAl]

We've seen our car slow down at a particular place twice. The freeway goes over a bridge there, and I'm looking forward to seeing if it happens again.

It did not slow down there today.

 

[TLLMRRJ]

It did not slow down there today.

Interesting.

 

[ewoodrick]

It's one thing to have a warning that says it's "beta code," and it's another to have a huge warning across the screen saying, "Hey, this software is so bad right now that it's a known bug that it will slam on the brakes when you least expect it, so you're probably going to get rear ended, and we ain't going to pay for no stinking damages or funerals."

Yes, the car does NOT "slam on the brakes" In an EV with regen, the transition from acceleration to no acceleration is relatively abrupt, because no acceleration really is braking with regen.
I've been through it many times, as a passenger, as you said, it's a "stupid driver" thing, but as a driver, you just ain't used to being a passenger.
Yes, it's not right. And while everyone talks about getting rear ended, I don't think that many, if any actually have been. And honestly, if they had been, the driver behind is way to close.

You can complain about it all you want. At this point is a fact of life and well over a 1/2 million people live with it.

 

[TLLMRRJ]

Yes, the car does NOT "slam on the brakes" In an EV with regen, the transition from acceleration to no acceleration is relatively abrupt, because no acceleration really is braking with regen.
I've been through it many times, as a passenger, as you said, it's a "stupid driver" thing, but as a driver, you just ain't used to being a passenger.
Yes, it's not right. And while everyone talks about getting rear ended, I don't think that many, if any actually have been. And honestly, if they had been, the driver behind is way to close.

You can complain about it all you want. At this point is a fact of life and well over a 1/2 million people live with it.

I think you are wrong. The car is perfectly capable of applying the brakes. It has to for collision avoidance. It's definitely braking harder than I experience with any level of regen braking.

And yes, people do drive too close. Can't stop all tailgaters at all times, but the last thing you want to do is brake check them, and if there's dashcam video, you will be at fault if you do brake check someone in my state.

You need to get past the "fact of life" to see the point of this thread, which is to better understand the situations that cause the code to slam on the brakes and what we can do to help Tesla, if anything. If you don't want to participate, I am very ok with that, but quit trying to silence us.

 

[ulrichw]

I think you are wrong. The car is perfectly capable of applying the brakes. It has to for collision avoidance. It's definitely braking harder than I experience with any level of regen braking.

[...]

I think ewoodrick has a good point, while also at the same time agreeing with you that the car can apply the brakes.

Nonetheless, I think perhaps the explanation of your perception lies in the definition of "jerk" from a physics perspective.

In Physics, jerk is defined as the rate of change in acceleration.

In a car, if you're driving this translates into how abruptly (vs. how hard) you apply the brakes.

Humans tend to perceive jerk more than absolute acceleration - basically if you apply the brakes very gradually and build up to full braking, it won't feel like you're braking as "hard" as it would if you very quickly and abruptly apply 50% braking force.

Your body's reaction is the same - if the force gradually changes, you will brace and adjust your position against the force. A high-jerk change in acceleration, on the other hand, will cause the exact reaction you described in your wife.

I think the issue here is that the autopilot in these situations acts extremely abruptly (i.e., creates a lot of "jerk").

In the cases where my car has behaved this way, I didn't feel like it was applying a large amount of braking, but it certainly was abrupt (and also due to its unexpectedness, somewhat startling).

For a good explanation with graphics see the answer to this stackexchange question: How to brake 'beautifully'?

 

[PianoAl]

>>We've seen our car slow down at a particular place twice. The freeway goes over a bridge there, and I'm looking forward to seeing if it happens again.

It did not slow down there today.

It happened again today at the same spot—wow. Dramatic. It was down to 40 MPH (from 65) when I stepped on the accelerator. No other cars around.

It was right here, and I wonder whether the circled thing scared it:

 

[Vanteer]

I experience this last week. As you can see I the picture, there was a tow truck stopped on the left side of the freeway. Car did an abrupt slow down from 70mph. I had read about this behavior, so I was somewhat prepared to punch the go pedal and override the breaking. Still kinda freaked me out.

Just noticed the “Adjacent Lane Speed” feature. This slows down the car when it detects slower side traffic. Lots of warnings in the manual under “Traffic-Aware Cruise Control”.

 

[Sidetracked]

I'm a new owner (about a month) and really love the car, but this issue does bother me. It's happened to me twice, and has made me hesitant to use my the cruise control unless the freeway is pretty empty.

I agree with the previous poster who wished that there was an option for an old fashioned 'set speed' cruise along with the more advanced version. (I'm pretty sure some cars do offer both adaptive and non adaptive CC).

I have no doubt this issue will ultimately get tweaked down to a rarity, but while that refinement process is ongoing, I don't love that my choices are no cruise control on a long trip, or feeling I have to be worried about any car following me.

 

[mattack4000]

Oh boy, you guys shouldn't even try autopilot

 

[Sophias_dad]

My 3 pretty much brake-checked a propane truck in the empty right lane of a three lane highway on Friday. Happily he was far enough back and Stacy's Mom was happy to re-accelerate to highway speed that he had no trouble not colliding with me. Not sure he even had to hit his brakes. Had I been in a less-speedy car or paying less attention, it could have gotten dicey. Its unlikely I could pay less attention, with the level of braking going on. It was way more than regeneration. I even recorded it, and I might try to edit it up for a show...like this one...

A side trip to Franklin on Christmas Eve would be fun, I guess.... : IdiotsInCars

 

[DaveRZ]

It happened again today at the same spot—wow. Dramatic. It was down to 40 MPH (from 65) when I stepped on the accelerator. No other cars around.

It was right here, and I wonder whether the circled thing scared it:

View attachment 506539

My guess would be that the GPS wasn't totally sure if you were on the highway or the offramp on the right.

I have a similar thing happen to me in the same spot each day on a new road (about 1 year old), where it joins up with where the old road used to be. New road's speed limit is 55, old road was 40. Quick slow down to 40 every time I pass a certain spot. I've learned to not use my TACC there. Someday the map data will be updated, and/or signs will be read and the problem will probably go away.

 

[camalaio]

I feel this is how the SC’s can get away with saying “Oh, that’s normal. My car does it too”

Absolutely. It's the same with my issue (to this day) of mine hugging the left and even crossing lane lines. "Operating within expectations". Pretty easy when the expectation is only that you hopefully stay mostly on the road. Tesla knows this isn't all optimal and is prepared to not have given consumers an expectation that it's any better than it is. They're good at this.

Yes, the car does NOT "slam on the brakes" In an EV with regen, the transition from acceleration to no acceleration is relatively abrupt, because no acceleration really is braking with regen.
I've been through it many times, as a passenger, as you said, it's a "stupid driver" thing, but as a driver, you just ain't used to being a passenger.
Yes, it's not right. And while everyone talks about getting rear ended, I don't think that many, if any actually have been. And honestly, if they had been, the driver behind is way to close.

You can complain about it all you want. At this point is a fact of life and well over a 1/2 million people live with it.

Agreed, but I think the main concern is that a human driver (I know, I know) wouldn't suddenly slow down in the middle of an otherwise clear highway for a second or two. The "fact of life" we have to deal with is something Tesla (and all manufacturers of these systems) should also have to deal with. That is, they should (and are probably trying) account for the fact that aggressive and sudden slowdowns may be a very dangerous thing to do on the highway because someone might hit you.

The only reason I wasn't hit in one especially nasty event was because the driver behind me was very quick to react and had good tires, and I also accelerated to override the slowdown. They still got uncomfortably close. Any small thing could have made that worse (other driver had worse tires, either of us reacted slow because we're tired, etc.).

Being rear-ended with these phantom slowdowns likely wouldn't be catastrophic (most likely bumper cover damage), which means it could have also happened and we just haven't heard of it more because it's mostly an inconvenience rather than a fatally serious issue.

 

[ewoodrick]

Absolutely. It's the same with my issue (to this day) of mine hugging the left and even crossing lane lines. "Operating within expectations". Pretty easy when the expectation is only that you hopefully stay mostly on the road. Tesla knows this isn't all optimal and is prepared to not have given consumers an expectation that it's any better than it is. They're good at this.



Agreed, but I think the main concern is that a human driver (I know, I know) wouldn't suddenly slow down in the middle of an otherwise clear highway for a second or two. The "fact of life" we have to deal with is something Tesla (and all manufacturers of these systems) should also have to deal with. That is, they should (and are probably trying) account for the fact that aggressive and sudden slowdowns may be a very dangerous thing to do on the highway because someone might hit you.

The only reason I wasn't hit in one especially nasty event was because the driver behind me was very quick to react and had good tires, and I also accelerated to override the slowdown. They still got uncomfortably close. Any small thing could have made that worse (other driver had worse tires, either of us reacted slow because we're tired, etc.).

Being rear-ended with these phantom slowdowns likely wouldn't be catastrophic (most likely bumper cover damage), which means it could have also happened and we just haven't heard of it more because it's mostly an inconvenience rather than a fatally serious issue.

Human drivers slow down in the middle of the road for all sorts of reasons.
The classic brake check is a great example of one of these situations. And it generally occurs because the driver in the rear is too close to begin with.
If the cars does slow, then there should be plenty of room for the car behind to brake, if not, then pretty much by definition and law, they are following too closely.

And I see slowdowns for other reasons all the time. "Oh no, I missed my exit"

But generally, the slow downs, only feel worse than they are. Any shift from acceleration to no acceleration in an EV seems to feel like inadvertent braking.

 

[camalaio]

Human drivers slow down in the middle of the road for all sorts of reasons.
The classic brake check is a great example of one of these situations. And it generally occurs because the driver in the rear is too close to begin with.
If the cars does slow, then there should be plenty of room for the car behind to brake, if not, then pretty much by definition and law, they are following too closely.

And I see slowdowns for other reasons all the time. "Oh no, I missed my exit"

But generally, the slow downs, only feel worse than they are. Any shift from acceleration to no acceleration in an EV seems to feel like inadvertent braking.

I think we can agree there's a very large difference between the objectionable practice of intentionally and dangerously brake-checking those behind you versus AutoPilot suddenly reacting to something that isn't there in front of it.

I'm not saying people don't slow down for all sorts of reasons, but why excuse more slowdowns for no reason simply because people act aggressively (with intent) and dangerously (with intent)?

I'll stand by my view that the slowdowns seem bad because they are. Neither passengers nor other drivers on the road seem to be expecting it, and this isn't a feeling somehow only introduced by the fact it's an EV. If a gas-powered vehicle applied brakes to get the same amount of slowdown so suddenly, it would still feel the same.

 

[ewoodrick]

I think we can agree there's a very large difference between the objectionable practice of intentionally and dangerously brake-checking those behind you versus AutoPilot suddenly reacting to something that isn't there in front of it.

I'm not saying people don't slow down for all sorts of reasons, but why excuse more slowdowns for no reason simply because people act aggressively (with intent) and dangerously (with intent)?

I'll stand by my view that the slowdowns seem bad because they are. Neither passengers nor other drivers on the road seem to be expecting it, and this isn't a feeling somehow only introduced by the fact it's an EV. If a gas-powered vehicle applied brakes to get the same amount of slowdown so suddenly, it would still feel the same.

No, I don't agree with your statement, just the opposite.

From a "car behind you" what's the difference? Nada, they just see the car slowing.
For "no reason", I disagree, the car saw a reason. It thought that there was a need. Maybe if you saw the world through the car's eyes, you may think differently.
And I've been riding with my wife in both the Tesla and Leaf over the last few days. Unexpected slow downs happened much more when she was driving than when the car was driving.

 

[camalaio]

No, I don't agree with your statement, just the opposite.

From a "car behind you" what's the difference? Nada, they just see the car slowing.
For "no reason", I disagree, the car saw a reason. It thought that there was a need. Maybe if you saw the world through the car's eyes, you may think differently.
And I've been riding with my wife in both the Tesla and Leaf over the last few days. Unexpected slow downs happened much more when she was driving than when the car was driving.

I don't want to go back and forth too much, however...

• You stated brake checking happens due to people behind following too close (presumably an intentional "get off my arse!" signal). That is, the car/person doing the braking is reacting to something behind it. As far as anyone can tell, Tesla AP does not attempt to participate in such petulant road behaviour and is instead looking at the road ahead and beside for where to go and any risks.
• Perhaps I should have said "no factual reason with a irrefutable grasp of reality and what a reasonable driver would have done". If we don't like the word "reasonable" being used here, we'd need to even rethink how legal trials are done.
• I ain't bringing anyone's wife into this

 

[ewoodrick]

I don't want to go back and forth too much, however...

• You stated brake checking happens due to people behind following too close (presumably an intentional "get off my arse!" signal). That is, the car/person doing the braking is reacting to something behind it. As far as anyone can tell, Tesla AP does not attempt to participate in such petulant road behaviour and is instead looking at the road ahead and beside for where to go and any risks.
• Perhaps I should have said "no factual reason with a irrefutable grasp of reality and what a reasonable driver would have done". If we don't like the word "reasonable" being used here, we'd need to even rethink how legal trials are done.
• I ain't bringing anyone's wife into this

And you are missing my statement.

To the car behind you, what is the difference?

And while a reasonable driver may not have slowed at that exact same point

• There are many other places that reasonable drivers do exhibit unreasonable behavior unexpectedly
• What about the unreasonable drivers?

 

[camalaio]

And you are missing my statement.

To the car behind you, what is the difference?

And while a reasonable driver may not have slowed at that exact same point

• There are many other places that reasonable drivers do exhibit unreasonable behavior unexpectedly
• What about the unreasonable drivers?

Ah OK, I think we've gone off on different tangents.

I was speaking to the fact that unexpected slowdowns are bad from the perspective of the driver, whereas you're talking from both that perspective and the perspective of other drivers. As the intent of this thread is to narrow down on what causes "phantom braking", I was only thinking of the perspective of what the car should be doing and not what other drivers are seeing necessarily. My point about the driver behind almost hitting the Tesla may have implied otherwise, but the problem I was trying to highlight was that there was nothing in front of or beside the Tesla that should have caused it to slow down.

But going back to your perspective, there is actually a difference to the driver behind. The driver in front suddenly slowing is normally met with an internal "WTF" from the driver behind, indeed. This could be any sort of obstacle avoidance (perhaps not a perfect reaction but a valid one) or as you pointed out, reacting too late to something like an exit (which is poor reaction). As humans though, we are generally able to distinguish between these events and someone actively trying to piss us off with brake checking. The communicated aggression is absolutely perceivable even though the "body" in this "body language" is a hunk of steel. This is because the way in which the braking is performed is much different, and usually brake-checkers will do so multiple times in succession unlike someone braking for one of the other above reasons.

Driving is actually a very social activity. This is more obvious in countries where people somehow generally survive despite an absolute lack of generally followed "Western" road laws and traffic control devices. But even in North America, many aspects of driving are social.

Back to the topic though, phantom slowdowns do occur. We both agree it's not ideal even if we don't agree on the specifics. As is shown by the discussion, driving safely is hard even before you add in misidentifying objects (which is just one of many theories on the source of phantom slowdowns) or GPS position (one of the more interesting ones given how AP handles speed limit changes).

Note to @TLLMRRJ : I forgot to mention, I don't think that contrast flash is anything to worry about or triggered the problem. I posted a thread previously here, but some people's cameras do just flash and AP doesn't seem bothered by it:

(the video isn't using AP, just demonstrating the flashing happens, especially in lower light conditions or cloudy days).

 

[p4594spa]

I use traffic aware cruise control about 98% that I am driving. I occassionally see the phantom slow down. I can't tell you whether it is the brakes or just full re-gen since they are so similar. What I have noticed virtually everytime is that I am in the right lane and there is a car exiting road to my right (who is obviously going slower than I am). For some reason the car gets confused by the slower (or stopped car in an exit lane) rather than focusing on the car ahead of me.

It has gotten so that when I see the situation I am now prepared to get on accelerator to override it.