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  • The final cut of TMC Podcast #27 is available now with topics time-stamped. We discussed: Consolidation in LiDAR manufacturers; Volvo EX90 shipping with LiDAR; FSD Beta Full Release in N.A.; FSD detecting autopilot cheats, Gwen Shotwell directly overseeing SpaceX Starship; and more. You can watch it now on YouTube. We should have it published to podcast networks shortly.

FSD and Phantom Braking on the Highway. It is Insane.

I have a 2022 with basic Autopilot. On the out of the factory software version I had one mild phantom braking incident, but after an update, and through many more, I have had zero. This is on SoCal freeways in clear weather.

Maybe going into FSD beta downgrades the highway stack as well?
Depends on what you mean by "downgrades." For a while, my wife's 2019 M3 wasn't on the FSD Beta stack while my 2018 M3 was. I would regularly drive to work, 20+ miles mostly on highway, in both cars, so I can say for certain there are differences in how FSDBeta drives on the highway vs the non-FSDb stack. I personally find the FSDb stack better at highway driving than the non-FSDb, but your mileage may vary.

My understanding these differences are mostly due to the FSDb stack being Vision-Only, while the other stack as of recently was not, but it seems like they're finally moving the old stack onto Vision-Only too, so likely the differences I noticed will go away. (I personally can no longer test this, as my wife's M3 was finally moved onto FSDb.)
 
I have version 2022.24.5 and still experience significant PB. What is unusual is that it occurred 2:30 am on a deserted 3 lane highway; specifically on Garden State Parkway often times near mile marker 61. The only thing I can say that might trigger the PB, is the lights on the overhead signs. It could result in an appearance of a crosswalk in the system otherwise there is no practical reason to set off the braking event.
 
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I think this may be something. I drove from NJ to Albany last Saturday night on 287/87. I experienced several mild phantom braking events near illuminated overhead signs. Otherwise flawless on 2022.24.6 - this autopilot not FSD for me. I also experienced what I first thought was pb when the car slowed briefly but it was displaying a message that it was slowing for emergency vehicle lights - police with flashers on other side of divided highway.
 
I have version 2022.24.5 and still experience significant PB. What is unusual is that it occurred 2:30 am on a deserted 3 lane highway; specifically on Garden State Parkway often times near mile marker 61. The only thing I can say that might trigger the PB, is the lights on the overhead signs. It could result in an appearance of a crosswalk in the system otherwise there is no practical reason to set off the braking event.
In the Seattle area we have toll cameras over HOV lanes and often times the car thinks it is a traffic light, as they momentarily appear, and the car starts to slow down, then the traffic rendering disappears. Sometimes it only shows for a brief second, but is enough to cause PB. This is definitely once of the sources of PB for me, but not the only one.
 
Since I got FSD beta and Tesla switched to a "vision only" system I have been having several random braking whether driving on interstate or state highways (2018 Model S). This happens noticeably when driving with no one in front of me. It has made highway travel an annoyance while having AP engaged as it randomly happens and speed can go from 70 MPH to 64 or even 50.

If there is a vehicle behind me and FSD/AP does phantom braking they wonder what's going on with me. If it happens more than once they get annoyed as they think I am brake checking them. I tried to clean the cameras and do a camera calibration. Nothing worked. I disabled FSD and it did not help. I disabled NoA and it did not help. I disabled Autosteer just to get tack working as even with tacc the car will randomly brake.

I sent an email to Tesla FSD beta requesting the removal of the software but honestly I don't know if I will get the software that uses radar and not a vision only system. Haven't heard back from Tesla yet. The current system is inferior on highway driving not to mention it is dangerous, consumes the tires and brakes, and makes driving less comfortable.

What would you suggest I do?
Try setting the following distance to the max of 7 when autopilot is engaged. Worked for me so far.
 
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I think this may be something. I drove from NJ to Albany last Saturday night on 287/87. I experienced several mild phantom braking events near illuminated overhead signs. Otherwise flawless on 2022.24.6 - this autopilot not FSD for me. I also experienced what I first thought was pb when the car slowed briefly but it was displaying a message that it was slowing for emergency vehicle lights - police with flashers on other side of divided highway.
The attached image is the event that causes phantom braking for my vehicle. This is almost reproducible every time I drive near this overhead sign.
The image shows a very mild curve behind the sign but nothing to indicate an approaching danger. I believe the illumination prior to the sign might washes out the road surface behind the sign. This may cause the TACC to be momentarily become confused and slows down until it is able to go beyond the overhead highway lights. The sign itself is not illuminated.
 

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The attached image is the event that causes phantom braking for my vehicle. This is almost reproducible every time I drive near this overhead sign.
The image shows a very mild curve behind the sign but nothing to indicate an approaching danger. I believe the illumination prior to the sign might washes out the road surface behind the sign. This may cause the TACC to be momentarily become confused and slows down until it is able to go beyond the overhead highway lights. The sign itself is not illuminated.
It's because it can't extend the lane lines well enough in it's pea brain that it's confident of the road being empty ahead---as in hypothetically it thinks there's a dropoff and there might be a stationary obstruction lying in wait so it slows to a speed where it thinks it can brake enough to stop before it.

I think it's not the sign but the shadow from the bridge and change in illumination.

I've seen lots of failure pictures with empty roads and undulations---this is a fake undulation from shadow. If there were cars ahead of you driving on it, there wouldn't be a problem, as it would see them and follow them knowing they were moving forward. Driving with light traffic is the best case it seems.

Maybe try setting 'following distance' to max on empty roads, and try again in this location? Maybe it uses that distance in its calculation? I never experience empty roads so I can't test this.
 
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It's because it can't extend the lane lines well enough in it's pea brain that it's confident of the road being empty ahead---as in hypothetically it thinks there's a dropoff and there might be a stationary obstruction lying in wait so it slows to a speed where it thinks it can brake enough to stop before it.

I think it's not the sign but the shadow from the bridge and change in illumination.

I've seen lots of failure pictures with empty roads and undulations---this is a fake undulation from shadow. If there were cars ahead of you driving on it, there wouldn't be a problem, as it would see them and follow them knowing they were moving forward. Driving with light traffic is the best case it seems.

Maybe try setting 'following distance' to max on empty roads, and try again in this location? Maybe it uses that distance in its calculation? I never experience empty roads so I can't test this.
There are still cars with radar that is not disabled yet. Some people say they can still set following distance to 1 and AP to 90MPH. If this car still has radar enabled, this was a common source of PBs for cars - overpasses and large freeway signs.
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
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San Diego
It's because it can't extend the lane lines well enough in it's pea brain that it's confident of the road being empty ahead---as in hypothetically it thinks there's a dropoff and there might be a stationary obstruction lying in wait so it slows to a speed where it thinks it can brake enough to stop before it.

I think it's not the sign but the shadow from the bridge and change in illumination.

I've seen lots of failure pictures with empty roads and undulations---this is a fake undulation from shadow. If there were cars ahead of you driving on it, there wouldn't be a problem, as it would see them and follow them knowing they were moving forward. Driving with light traffic is the best case it seems.

Maybe try setting 'following distance' to max on empty roads, and try again in this location? Maybe it uses that distance in its calculation? I never experience empty roads so I can't test this.
Could be, but could also be connecting the lights and the yellow sign.

Maybe it decided lights were flashing.

Yellow signs with flashing lights usually lead to slowing (I have a test case where this happens prior to a traffic light around a bend in a downhill - flashing lights turn on/off synced with downhill light and car will jam on regen for them (unnecessary of course) only when they flash).

Not saying that is the case here; could be what has been suggested by you.

Also anything that looks orange next to freeway can lead to braking. (Not the case here.)

Lots of tiny stimuli can lead to these things, I discovered on recent hundreds of miles of freeway driving. I review the video, and then I usually see the problem object.
 
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