TACC random slowing down

[connectjunkie]

Having some weird behaviour from TACC since updating to 2023.44.30.5.1 - TACC will randomly start slowing down for no reason. Happened 3 times in a recent 20 mile drive, including on a straight road with no cars in sight.

Anyone else seeing this? I wouldn’t call this phantom braking - this is more like the slowing you get from regen.

 

[Pink Duck]

I’ve experienced that on a few rare occasions related to locations that repeat. Sometimes at nights, some in daylight, always dry. There’s no warning at all, the car just starts progressively slowing to a ridiculous speed around 50% of speed limit then stays there for a considerably long time. Usually with no other vehicles or people/animals around. Cameras unobscured. Is puzzling, like a false positive from neural net training. Has the same feeling of what it might do if driver stopped responding, without the messages/light flashes.

 

[hgmichna]

Not random and not for no reason. In my observation it always has a trigger, always something that does not look quite kosher to the computer.

But it is probably over-sensitive. An oncoming car, wobbling in its lane; a pedestrian moving closer to the street's edge; something in front that might want to cross the road; something that looks like it could be an obstacle; etc. Most of the times I believe I can make out why it slowed.

I like it when the car slows down ever so slightly to alert me to a possible danger, but when it slows down too much, it becomes a nuisance.

 

[DoricJim]

They’ve really messed up TACC recently and am having the same issue at times. Wet weather (even very minor rain or drizzle) is causing real issues with TACC now. Posted about this in the Holiday update thread.

 

[ATPMSD]

Me too, really annoying.

 

[Fursty Ferret]

Yes, I can understand it in situations with reduced visibility but sometimes it does it on quiet random roads with clear markings.

 

[ajmorr.is]

They’ve really messed up TACC recently and am having the same issue at times. Wet weather (even very minor rain or drizzle) is causing real issues with TACC now. Posted about this in the Holiday update thread.

Funny really because I drove from Manchester to Liverpool last night in the dark and almost biblical rain and TACC didn’t miss a beat, even when the screen was overwhelmed with sudden spray and took the time it took for the wipers to do another swipe to clear it was still fine.

 

[DoricJim]

Funny really because I drove from Manchester to Liverpool last night in the dark and almost biblical rain and TACC didn’t miss a beat, even when the screen was overwhelmed with sudden spray and took the time it took for the wipers to do another swipe to clear it was still fine.

Do you have a vision only vehicle or did it have radar originally? There seems to no obvious rhyme or reason why some have issues and others don’t. Speculating, maybe newer vision only cars cope better than those which used to have radar?

I have a December 2021 M3 for reference.

 

[fhteagle]

I see the unexplainable slow down mostly on gentle to moderate curves. Ones that even a new driver would take at the speed limit, TACC wants to go to limit -8, then hunt up and down constantly by 3 mph or so, in a very jerky, nauseating, and car destabilizing fashion.

On traffic crossing the path ahead in plenty of time to not even need to slow down at all, TACC instead goes into emergency level braking for.

It's bad enough that if the next update doesn't put in a manual dumb cruise control, or fix TACC, we're probably selling the car after less than one year since new in service date. Yes it's that bad.

 

[connectjunkie]

Do you have a vision only vehicle or did it have radar originally? There seems to no obvious rhyme or reason why some have issues and others don’t. Speculating, maybe newer vision only cars cope better than those which used to have radar?

I have a December 2021 M3 for reference.

For reference I have a first shipment Model Y, so radar and USS

 

[Woody5575]

I’ve had this issue on an interstate. I was on TACC at 75 mph (without steering assist) in the right lane, with no cars around me. When I passed an off ramp, the car slowed fairly abruptly and was at 65 when I caught it and hit the accelerator. At the very next off ramp, it did the same thing. I’ve had this happen one other time, and I think it was at the same place, under the same circumstances. I think the car expects me to follow the right side lane marker that veers off to the right, so it starts to slow to an appropriate speed. I plan to test this theory at some point, but it seems odd that it would assume I would be exiting the interstate.

 

[sdbonez]

Seeing the same thing but can't tell if it's due to any of the recent updates with my 23MYP. Last night, the triggers in my case seemed to be orange/yellow reflector signs meant to mark hazards but I don't think it slowed in the same spot previously.

 

[Tony Hoyle]

I’ve experienced that on a few rare occasions related to locations that repeat. Sometimes at nights, some in daylight, always dry. There’s no warning at all, the car just starts progressively slowing to a ridiculous speed around 50% of speed limit then stays there for a considerably long time. Usually with no other vehicles or people/animals around. Cameras unobscured. Is puzzling, like a false positive from neural net training. Has the same feeling of what it might do if driver stopped responding, without the messages/light flashes.

I've seen videos of it on youtube.. straight road, no obstructions, just slows down for no reason.

I suspect it's mapping errors ie. the car isn't using the displayed speed limit it's using something else within the mapping, and it's wrong.

 

[ATPMSD]

I suspect it's mapping errors ie. the car isn't using the displayed speed limit it's using something else within the mapping, and it's wrong

Totally agree, this is what I see as well. But Elon believes his Tesla Vision can do it all! LOL

 

[Mr Speirs]

Yes noticed in the last couple of updates that the TACC and the Autopilot have seemed to have got worse. To the point I turned to my wife and said that they are pretty much unusable now. The amount of random slow downs whilst overtaking on motorways, emergency braking because it thinks the car in completely the other lane is too far over, the auto-wipers not working...either on when there's no rain or nothing when completely obscured, the auto headlights being utterly useless. If they turned the auto-wipers and lights so they weren't the default with switching to Autopilot that would help a bit...but as far as I can tell TACC and Autopilot are going in the wrong direction fast!

 

[Pagemakers]

I suspect it's mapping errors ie. the car isn't using the displayed speed limit it's using something else within the mapping, and it's wrong.

Don’t think mapping has anything to do with it. The map is kind of irrelevant. The car drives with what it sees. Vision-only is the killer.

 

[ajmorr.is]

Do you have a vision only vehicle or did it have radar originally? There seems to no obvious rhyme or reason why some have issues and others don’t. Speculating, maybe newer vision only cars cope better than those which used to have radar?

I have a December 2021 M3 for reference.

MY23 Model Y, no radar or even USS.

 

[MrBadger]

Don’t think mapping has anything to do with it. The map is kind of irrelevant. The car drives with what it sees. Vision-only is the killer.

Sort of. If speed limit signs are not detected every xxx distance then the vehicle speed limit reverts to being determined from mapping.

One of my routes that I use as a behaviour reference has a junction where speed limit incorrectly changes due to speed different speed limit signs on the joining road. Even though the car incorrectly uses these to set the speed limit, within a few hundred yards it reverts back to the correct speed limit for the road even though it does not pass any additional speed limit signs. I did check OSM for this section of road (without getting into discussion where Tesla source their speed limits from) and it seemed to correlate with the boundary between mapped road segments.

Probably also explains why detected motorway gantry variable speed limits sometimes revert back to 70 before the next gantry with same temporary speed limit.

This behaviour is/was documented in the manual.

 

[Pagemakers]

Sort of. If speed limit signs are not detected every xxx distance then the vehicle speed limit reverts to being determined from mapping.

But in my car the speed change can be detected by the car from say 70 to 60 and only in a very small percent of these instances does my car slow down. In most cases it carries on at the pre-set level.

However, I think what is happening here has nothing to do with that. I can be driving down the motorway at 70. No cars, shadows or signs in sight and the car will randomly hesitate and slow down. Sometimes gently. Sometimes violently. Sometimes by a new mph and other by a huge chunk.

Next day, same place. Same conditions and it’s fine.

Vision-only is the culprit. It’s crap. Simple as.

 

[Hurricane]

But in my car the speed change can be detected by the car from say 70 to 60 and only in a very small percent of these instances does my car slow down. In most cases it carries on at the pre-set level.

However, I think what is happening here has nothing to do with that. I can be driving down the motorway at 70. No cars, shadows or signs in sight and the car will randomly hesitate and slow down. Sometimes gently. Sometimes violently. Sometimes by a new mph and other by a huge chunk.

Next day, same place. Same conditions and it’s fine.

Vision-only is the culprit. It’s crap. Simple as.

That is exactly my experience and it’s getting worse. While I never expected Level 4 autonomy anytime soon I did think there would be steady, incremental progress over the years. I didn’t for one second imagine that after four years of ownership FSD would actually be worse.

So much for “progress”.