Phantom Braking theory...need help to test this out

[haroldo]

I typically get phantom braking, once a week, or so. These are not associated with a dark shadow from an overpass (half the time I drive at dark, so shadows don't come into play)

Today the car started to slow/brake, The closest vehicle was ~1/2 mile behind me, so I let the car figure it out. Cruise control is set to speed limit +10%. The road has a 65 MPH limit, so the car was driving at 72. The braking event ended when it hit 65 (coincidentally, the speed limit) and then accelerated back to 72.

My theory ... maybe the glitch is related to the software in the "speed limit +XX%" system (for want of a better name). Is it possible that the system momentarily turned off, so the car thought it was supposed to be driving at actual speed limit (not plus XX%), thus it slowed/braked? Today, it didn't feel like the car was braking (with friction brakes), but rather the feeling you get with normal driving when you take foot off the accelerator at highway speed. Maybe it's really not phantom braking (implying brakes were applied to slow the car), but lack of acceleration (regen slowing). I didn't notice if the "maximum speed" display on screen changed, I don't think it did, but couldn't say for sure.

I have two things I'd like to ask of the community.
First, IF you are on an empty highway, with plenty of room behind you, and your car starts to slow/brake, ... paying attention to the traffic behind you...don't override... let the car continue braking until it's no longer safe to do so. Does the car eventually recover from the braking? If so, at what speed? Maybe we will find out what we believe is random braking, is the computer erroneously setting cruise control to the speed limit. I'm only interested in random slowing/braking, we all know in some instances it can be tricked (shadows. etc.).

Second, there's no shortage of phantom braking threads, most get overrun with hundreds of extraneous subtopic discussions, filled with complaints and anger directed towards Tesla. I get it. No one wants to spend $60-80 thousand on a car that doesn't work properly. My request is that we try to keep the thread on point, which is...if the car eventually figures out the braking and starts accelerating again, at what speed did the car recover?

This might be a useful piece of information for engineering.

Thanks!

 

[TAfirehawk]

Once a week.....geesh I was getting 400 a week before camera calibration on empty highways that has gotten it down to 100 a week. I would give my left arm for once a week............

The vehicle behind is not the issue but what it sees ahead of you. The PB can happen on a totally empty road and it see glare off the road going over a small hill/rise or simply see a vehicle 1/4 mile away and it think it is 100 feet away.

It recovers to proper speed once the system realizes how stupid it was in detecting a phantom object/vehicle.....

 

[DblOSmith]

I typically get phantom braking, once a week, or so. These are not associated with a dark shadow from an overpass (half the time I drive at dark, so shadows don't come into play)

Today the car started to slow/brake, The closest vehicle was ~1/2 mile behind me, so I let the car figure it out. Cruise control is set to speed limit +10%. The road has a 65 MPH limit, so the car was driving at 72. The braking event ended when it hit 65 (coincidentally, the speed limit) and then accelerated back to 72.

My theory ... maybe the glitch is related to the software in the "speed limit +XX%" system (for want of a better name). Is it possible that the system momentarily turned off, so the car thought it was supposed to be driving at actual speed limit (not plus XX%), thus it slowed/braked? Today, it didn't feel like the car was braking (with friction brakes), but rather the feeling you get with normal driving when you take foot off the accelerator at highway speed. Maybe it's really not phantom braking (implying brakes were applied to slow the car), but lack of acceleration (regen slowing). I didn't notice if the "maximum speed" display on screen changed, I don't think it did, but couldn't say for sure.

I have two things I'd like to ask of the community.
First, IF you are on an empty highway, with plenty of room behind you, and your car starts to slow/brake, ... paying attention to the traffic behind you...don't override... let the car continue braking until it's no longer safe to do so. Does the car eventually recover from the braking? If so, at what speed? Maybe we will find out what we believe is random braking, is the computer erroneously setting cruise control to the speed limit. I'm only interested in random slowing/braking, we all know in some instances it can be tricked (shadows. etc.).

Second, there's no shortage of phantom braking threads, most get overrun with hundreds of extraneous subtopic discussions, filled with complaints and anger directed towards Tesla. I get it. No one wants to spend $60-80 thousand on a car that doesn't work properly. My request is that we try to keep the thread on point, which is...if the car eventually figures out the braking and starts accelerating again, at what speed did the car recover?

This might be a useful piece of information for engineering.

Thanks!

It happened to me yesterday. Open country road. Very hilly with trees. Near dusk. AP engaged. 55mph. Phantomed down to 51. before recovering.

 

[vanjwilson]

Once I got over the initial shock of phantom breaking, I've also been trying to let the car recover on it's own. I've noticed the same thing the OP did. It slows down usually less than 5mph or so, and then quickly recovers. In my mind, that's no worse than following a driver who isn't using cruise control and unconsciously varies their speed.

Phantom breaking usually happens to me if I'm driving in early morning or late afternoon, and there's glare from the sun. Moreover, there are a couple of spots on a route I regular drive on the way back from hiking in the mountains, but only on my way back--not on the way there.

For what it's worth, I've seen one spot where I get "phantom acceleration", where the cruise control setting will increase from ~70mph to 79mph right after I merge onto I-85 northbound from US-74 eastbound in Gaston County, NC. That may be worse, but it always happens at the same spot so now I just expect it, bump it back down, and go on with my life.

 

[haroldo]

There’s two different things, phantom braking, and unexpected slowing (regen).
The former, more severe and aggressive , as the car is tricked into thinking there’s danger ahead.
The latter, might be a software bug, alternatively what Tesla describes as “the collective experience”. If 100 Teslas pass a specific spot and all slow from 70 to 60, the groupthink assumes there’s a reason, and will have your car slow (at least that’s what service rep told me).
In any event, I wondered if it would recover at speed limit, but a few posts here seem to say otherwise.

 

[Snerruc]

My car rarely phantom brakes, but with the last build, it now will light up saying brake with the alarm sounding not braking with nothing around. Also lately the navigate software is nuts. It will refuse to plan a course to a destination it has in the past.

 

[DarthStar]

My theory ... maybe the glitch is related to the software in the "speed limit +XX%" system (for want of a better name). Is it possible that the system momentarily turned off, so the car thought it was supposed to be driving at actual speed limit (not plus XX%), thus it slowed/braked?

I'm getting the phantom braking on the 5 freeway frequently in San Diego. I am not using "speed limit +xx." So far seems pretty random, but I will pay closer attention to help assess if it's part of your Tesla groupthink idea.

There is an intersection of a surface street near my house (speed limit 55) where despite the light being green, the car always brakes for it. It's a section of road that was just opened after years of construction. The Tesla Nav map still shows it as closed, so I assume that factors in to that specific instance. I just disable AP now as I approach that section on my way home.

Current SW 2021.11.102

 

[haroldo]

intersection of a surface street near my house (speed limit 55) where despite the light being green, the car always brakes for it

If you're using Red Light and Stop Sign, it's supposed to slow/brake, it is asking your permission to make sure the intersection is okay...except if you're following another vehicle, then it will continue through

 

[DarthStar]

If you're using Red Light and Stop Sign, it's supposed to slow/brake, it is asking your permission to make sure the intersection is okay...except if you're following another vehicle, then it will continue through

No, it's not that type of behavior which I'm familiar with at other intersections. At this particular intersection (with light green) it makes a hard deceleration/stop unless I intervene.

 

[Saxgod]

I have phantom breaking pretty consistently on any highway trip. Was on a straight and clear divided highway with no traffic today. Sun was high in the sky and visibility was unlimited. Cruising at 78mph (speed limit was 75). The car slammed on the brakes and slowed down to 45 mph( I allowed it to self resolve after making sure there was no one behind me). It then slowly rebuilt speed up to the speed limit. Before and after the incident it consistently break checks from 78 down to 74 and then recovers. Not a very relaxing ride. I captured the dash cam in case I needed it. There were heat mirages in the horizon. I wonder if these were the cause this time?

 

[haroldo]

Could an overpass have created dark shadow that tricked the car?

 

[Saxgod]

Could an overpass have created dark shadow that tricked the car?

There was no overpass. Just straight road no shadows.

 

[haroldo]

Not a great answer, but record the time, press the voice button and say "bug report phantom braking", press the dash cam button to record, go to app and set up a service call. Most likely nothing will get fixed initially, but it's possible that if engineering amasses enough of these incidents (the only way they'll get the info is if we report it), they might figure out the problem. Again, most likely a waste of your time, but that's the best solution (albeit not a very good one).

 

[SalisburySam]

Not a great answer, but record the time, press the voice button and say "bug report phantom braking", press the dash cam button to record, go to app and set up a service call. Most likely nothing will get fixed initially, but it's possible that if engineering amasses enough of these incidents (the only way they'll get the info is if we report it), they might figure out the problem. Again, most likely a waste of your time, but that's the best solution (albeit not a very good one).

Yeah, I understand the grasping at straws here. I’ve had PB since the car’s acquisition and still do on v32.22. Service call reported “operation of your vehicle is normal.” I’m guessing normal for Tesla, certainly not for me.

 

[clydeiii]

Probably best to revisit this topic after the FSD NN merges with the current NoA one.

 

[brianman]

Today the car started to slow/brake, The closest vehicle was ~1/2 mile behind me, so I let the car figure it out. Cruise control is set to speed limit +10%. The road has a 65 MPH limit, so the car was driving at 72. The braking event ended when it hit 65 (coincidentally, the speed limit) and then accelerated back to 72.

Maybe try setting your offset to 0 for a few weeks to see if the problem goes away? A pretty direct way to test your theory, no?

 

[haroldo]

Maybe try setting your offset to 0 for a few weeks to see if the problem goes away? A pretty direct way to test your theory, no?

If it occurred regularly, maybe, but the incidents are rare (none in three weeks)

 

[SylvainG]

I typically get phantom braking, once a week, or so. These are not associated with a dark shadow from an overpass (half the time I drive at dark, so shadows don't come into play)

Today the car started to slow/brake, The closest vehicle was ~1/2 mile behind me, so I let the car figure it out. Cruise control is set to speed limit +10%. The road has a 65 MPH limit, so the car was driving at 72. The braking event ended when it hit 65 (coincidentally, the speed limit) and then accelerated back to 72.

My theory ... maybe the glitch is related to the software in the "speed limit +XX%" system (for want of a better name). Is it possible that the system momentarily turned off, so the car thought it was supposed to be driving at actual speed limit (not plus XX%), thus it slowed/braked? Today, it didn't feel like the car was braking (with friction brakes), but rather the feeling you get with normal driving when you take foot off the accelerator at highway speed. Maybe it's really not phantom braking (implying brakes were applied to slow the car), but lack of acceleration (regen slowing). I didn't notice if the "maximum speed" display on screen changed, I don't think it did, but couldn't say for sure.

I have two things I'd like to ask of the community.
First, IF you are on an empty highway, with plenty of room behind you, and your car starts to slow/brake, ... paying attention to the traffic behind you...don't override... let the car continue braking until it's no longer safe to do so. Does the car eventually recover from the braking? If so, at what speed? Maybe we will find out what we believe is random braking, is the computer erroneously setting cruise control to the speed limit. I'm only interested in random slowing/braking, we all know in some instances it can be tricked (shadows. etc.).

Second, there's no shortage of phantom braking threads, most get overrun with hundreds of extraneous subtopic discussions, filled with complaints and anger directed towards Tesla. I get it. No one wants to spend $60-80 thousand on a car that doesn't work properly. My request is that we try to keep the thread on point, which is...if the car eventually figures out the braking and starts accelerating again, at what speed did the car recover?

This might be a useful piece of information for engineering.

Thanks!

How about setting the speed limit +0% ? Would it happen then?

 

[MyWhiteY]

I started on a trip to Florida yesterday. I love driving my MY. Had one incident of PB approaching an overpass on the highway yesterday. I'm going to try setting the speed limit to +0 and see what happens. I won't use autopilot on a two lane road due to too many PB. I do like auto pilot though. I was wondering if I subscribed to FSD for one month whether that would update the auto pilot software?? (I really don't have a need for beta FSD)

 

[Sporty]

I have phantom breaking pretty consistently on any highway trip. Was on a straight and clear divided highway with no traffic today. Sun was high in the sky and visibility was unlimited. Cruising at 78mph (speed limit was 75). The car slammed on the brakes and slowed down to 45 mph( I allowed it to self resolve after making sure there was no one behind me). It then slowly rebuilt speed up to the speed limit. Before and after the incident it consistently break checks from 78 down to 74 and then recovers. Not a very relaxing ride. I captured the dash cam in case I needed it. There were heat mirages in the horizon. I wonder if these were the cause this time?

Phantom brake. My wife: “shut that thing off”.