Phantom Braking

[Tronguy]

Just to add to the clamor. We experienced three closely spaced incidents of phantom braking with our Model Y while using cruise control without lane assist on highway 395 between Lone Pine and Bishop, California on Saturday 25 June. We've had the car since January 2022, and this was a (shocking) first. Haven't dared to use cruise control since. We have since updated to software version 2022.16.2. I guess we'll have to see if this took care of it. This is my first big disappointment with Tesla. My second is that it is impossible to find a way to report the issue to Tesla itself (other than the bug report which should be done on the spot). I have filed a report with NHTSA. Until the issue is fixed -- and from what I can tell, Tesla never really does fix phantom braking -- I wonder if it can be prevented by turning off emergency braking when using cruise control...?

And there's different flavors of "phantom braking". Let's give them classes: Class A is a full-on emergency stop. Somehow, the car has the idea that there's an elephant straight ahead. In this Class, the car's wheels aren't screeching, but that's only because Tesla's have anti-lock brakes.

Class B is a bit of a slow-down, say, from 65 mph to 60 mph. It's noticeable, not wonderful, but, unless one is being tailgated, not dangerous. At least in the sense that one does have the time to react and hit the gas without other traffic getting seriously freaked out.

The car over here is a 2018 M3 LR. Never have had a Class A. Class B's were a lot more common in 2018 and, over time and software updates, have become a lot less common. The trigger is usually a shadow across the highway, and that includes from trees and overpasses. The Class B events seem not to have been affected one way or the other by the use or lack thereof of the car's RADAR system.

So, was they near-screech, high-G halt attempts? Or a less dramatic but unnerving slow-down?

 

[GtiMart]

I can add other types which I do NOT consider phantom braking but some people call as such:
- the car is going up a hill and reaching the crest, it slows down because it temporarily cannot see far enough ahead to feel safe. It will accelerate back after the crest.
- The road changes speed limit so the car slows instead of keeping the "cruise control set speed".
- The car thinks it's on a service road instead of the main highway, possibly because of gps inaccuracy / bad internal maps. Speed limit is lower there so the car slows down.

You might call these variations of the Class B indicated higher up but they are not "phantom" brakings, they all have a good explanation and they are "by design". They are frustrating, but not "phantom"

Another case is when the car sees a car/truck in the opposite direction that brushes the center line (not on a highway, on a road that "crosses") and the car panic brakes because it thinks it's not safe.
Another variation of this is following a car that we know will have time to make a turn before we reach it, yet the car slows down hard just in case the other car in front doesn't turn.
Note: some of these are pretty high Gs, accompanied by screeching beeps inside the car. My wife has a heart attach each time, and I let out a swear word every time... Now, since Autopilot is really only suited for highways, I have no grounds to complain here.

There are many like this which I explain as "the car is driving like a panicked grandpa" but they have no choice but to program it that way. Even then, some people complain sometimes that the car drives like a cowboy... We all have our tolerances and preferences....

 

[Tam]

Can you explain what exactly happened in a bit more detail? I've seen people attribute all sorts of braking situations to "phantom braking" and not all of them are.

Tesla calls, in its release notes, this kind of behavior as "false slowdowns".

It's academic to deny that it's not true phantom brakes.

Whatever people call it, it's just not desirable, not normal and it needs to be fixed.

That means if this a DMV test, the driver would be flunked and if there’s a police behind, that's a brake checking ticket.

 

[msfeather]

That's a little difficult to describe, but I would say it was more of the near-screech variety. I say this because the car was breaking very hard, certainly harder than a 65 to 60 mph slow down, though not screeching or fishtailing, and only stopped braking when I got out of cruise control. I was so flustered that I don't remember whether I hit the brake, the accelerator or flicked up the drive stalk, or all of the above. So my impression was that the car was trying to come to a complete stop, though I can't know this for sure. I can tell you that we were all thrown forward somewhat by the force of the braking.

 

[msfeather]

There was no change in zoning or speed limit. Just miles of fairly straight, well-maintained highway at a constant speed limit with dry, hot sunny conditions. Not too much traffic. As stated above, one of the incidents took place with absolutely no one around me. For the other two, there was a car in the lane to the right of me, and that car was well under control and not drifting into my lane. Very little by way of shadows on the road given the desert-like conditions of that part of the state.

 

[GtiMart]

ok, thanks. One other slowdown reason is if you're passing people that are slower in the adjacent line. Sometimes the car will preventatively slow down so as to not pass those other cars too fast. I believe there's a graphic on screen when that happens (carets). Not a harsh slowdown, just thought I'd mention as we're listing various explanations for slowing down.

 

[chan_man]

I have experienced a certain location on the highway I travel everyday. the slowdown will happen at the same spot and when it happens I can see the speed limit change from 55 to 40 and right back to 55 in a second, Looks like a leftover when the road was being worked on a couple of years ago

 

[msfeather]

Thanks to all for these responses. These are interesting possibilities that I will try to monitor when and if it happens again.

 

[pontelaspilas]

anyone ever setup an autopilot caravan to see if the phantom braking is consistent?

 

[GtiMart]

You wouldn't know if your car is braking because the car is front is braking or if you have the same issue

 

[nate704]

 

[Tronguy]

There was no change in zoning or speed limit. Just miles of fairly straight, well-maintained highway at a constant speed limit with dry, hot sunny conditions. Not too much traffic. As stated above, one of the incidents took place with absolutely no one around me. For the other two, there was a car in the lane to the right of me, and that car was well under control and not drifting into my lane. Very little by way of shadows on the road given the desert-like conditions of that part of the state.

OK. So, if you had what we'll term for the moment a "Class A", that sounds like, "PANIC!" on the car's part. This isn't normal. A little bell is going off in the back of my head saying that there was some discussion/news articles about this kind of thing roughly a year ago and, if memory serves, I think the answer was, "Call Tesla".

Figure out in the "Schedule Service" area this would come up, put in a description of the problem (they leave lots of room for a description), and see what they say. Saying this carefully, you may be looking at some kind of hardware fault. IF this is the problem, then a new car is where it would happen. There's a term in hardware reliability called, "Infant Mortality", which describes the early part of the bathtub curve, where new stuff was tested, passed, escaped the factory, and then failed later. It's why there's warranties.

Finally: With a new car you get the cam.

1. If the car thinks there'll be an accident, it saves the clip. So, check the list of videos and see if it's in there. They're marked by time and date, so that shouldn't be hard.
2. You can save clips on demand so they don't go away.
   1. Hit the cam symbol and it'll save.
   2. Set the options so it'll save cam data on honk. Do that now, so, when this happens again, after recovering from the heart attack, you can honk and save the clip.
      

Sending the clip off to Tesla on a service request will likely (a guess) get you more attention then describing the action without the clip.

 

[Dewg]

OK. So, if you had what we'll term for the moment a "Class A", that sounds like, "PANIC!" on the car's part. This isn't normal. A little bell is going off in the back of my head saying that there was some discussion/news articles about this kind of thing roughly a year ago and, if memory serves, I think the answer was, "Call Tesla".

Figure out in the "Schedule Service" area this would come up, put in a description of the problem (they leave lots of room for a description), and see what they say. Saying this carefully, you may be looking at some kind of hardware fault. IF this is the problem, then a new car is where it would happen. There's a term in hardware reliability called, "Infant Mortality", which describes the early part of the bathtub curve, where new stuff was tested, passed, escaped the factory, and then failed later. It's why there's warranties.

Finally: With a new car you get the cam.

1. If the car thinks there'll be an accident, it saves the clip. So, check the list of videos and see if it's in there. They're marked by time and date, so that shouldn't be hard.
2. You can save clips on demand so they don't go away.
   1. Hit the cam symbol and it'll save.
   2. Set the options so it'll save cam data on honk. Do that now, so, when this happens again, after recovering from the heart attack, you can honk and save the clip.

Sending the clip off to Tesla on a service request will likely (a guess) get you more attention then describing the action without the clip.

You can also press the voice button and say "bug report" and it will save a special file that includes cam and telemetry on all systems in the car. Only service can access those reports.

 

[chyuan]

I have experienced a certain location on the highway I travel everyday. the slowdown will happen at the same spot and when it happens I can see the speed limit change from 55 to 40 and right back to 55 in a second, Looks like a leftover when the road was being worked on a couple of years ago

I had similar experience on a particular part of freeway I travel somewhat frequently, it suddenly thinks the speed limit is 55 instead of 65, and it will attempt to hard brake it down from whatever speed (usually ~75 without traffic) to 55 when there is no speed limit sign in sight, I’m guess it suddenly thinks it’s no longer on the freeway and imposes a lower max speed and thus the hard brake, but whatever the cause there no excuse this is a bug…

 

[sleepydoc]

I had similar experience on a particular part of freeway I travel somewhat frequently, it suddenly thinks the speed limit is 55 instead of 65, and it will attempt to hard brake it down from whatever speed (usually ~75 without traffic) to 55 when there is no speed limit sign in sight, I’m guess it suddenly thinks it’s no longer on the freeway and imposes a lower max speed and thus the hard brake, but whatever the cause there no excuse this is a bug…

This isn’t a bug but a case of the system behaving as expected but having incorrect data. The end result is the same, but the cause is different.

Having the car automatically adjust the speed to the speed limit seems like a simple task but is more difficult than it would initially seem. If you turn onto a road and there’s no sign, what do you use for a speed limit? The system needs to have some sort of database to fall back on. Now, once you have that database, how do you decide which data to use, the signs or the database? It’s easy to say ‘use the signs,’ but how does the car know whether the database is wrong and the speed limit is really 65 or if it missed the sign because it was obscured, driving next to a truck, etc, and it’s supposed to slow down?

 

[Dewg]

It can also be a challenge based on location - for example, California has a few rules:

1) Unless otherwise posted, the maximum speed limit is 55 mph on a two-lane undivided highway and for vehicles towing trailers.

2) The speed limit for a blind intersection is 15 mph. An intersection is considered “blind” if there are no stop signs at any corner and you cannot see for 100 feet in either direction during the last 100 feet before crossing. If your view is blocked, move slowly forward until you can see.

3) Residential, the speed limit is 25 mph, unless otherwise posted. Also, in school zones, when children are present.

Tesla cannot currently read signs beyond standard speed limit signs, so school zones are a problem for now. I manually lower the speed using the wheel when near a school. I've also noticed that blind intersections are not taken at 15MPH, usually posted limit (or 25). You may need to lower the speed yourself in these situations.

 

[GoPowerup]

Has anyone insured acceleration boost with Geico insurance on your model 3 LR?

If so, how did you do it and how much was the premium increase?

I am unable to see software upgrade under the performance modification.

Thank you

 

[mjnicho1]

Does anyone know if Tesla will return to using Lidar radar to solve the phantom braking problems while in auto pilot mode, now that the cost of Lidar radar has come way down to like a $1000.00?

 

[CKwik240]

I doubt there is any mechanism for Geico to find out...

 

[Tam]

Does anyone know if Tesla will return to using Lidar radar to solve the phantom braking problems while in auto pilot mode, now that the cost of Lidar radar has come way down to like a $1000.00?

Unless you hear from íniders but publicly, Tesla has repeatedly confirmed the position of anti-LIDAR.

In addition, Tesla does cite anti-sensor-fusion as a reason to delete the radar and go for pure vision only.

LIDAR is currently active in most cars that are not sold to consumers like Waymo, Cruise...