[Craig Bennett]

I’ve seen degradation in TACC behavior similar to what you are describing in the last several releases. This is especially true when changing lanes. I see no known reason - shadows, other cars, birds, ghosts, anything!

The pattern seems to be that a regression seems to last several iterations before it gets addressed, at which time a new regression sometimes gets introduced.

This is the price of rapid new feature introduction. I generally don’t use a particular feature until I see enough feedback from other users that it appears stable.

 

[Olds442]

i have the issue on a couple roads that have frontage roads, where it's reading the speed limit on the frontage when i'm in the fast lanes.

i was on one of those roads yesterday that i posted about above, Palatine Road in Arlington Heights, and it read the correct speed for the fast lanes this time. it's the first time it's done that and i drive on that stretch often.

kinda eerie since i just posted about it and now it's fixed, cue the twilight zone music.

 

[Kimmo57]

First off, I really wish Tesla would offer just ordinary cruise control so that I don't have to continually monitor my speed while cruising on the highway, because the "active" cruise is unusable in it's current form. It randomly changes it's setpoint while I'm cruising on the freeway, making my car suddenly decelerate for no reason. It's not only annoying, it's dangerous. Today on the way to work it just suddenly changed from a setpoint of 73 mph to 30 and began braking hard. This happened in broad daylight and good weather when there were no other cars for several hundred yards in front of me (not that it'd be OK for it to do this in any conditions). As a separate issue, it will frequently (like perhaps once or twice per mile) slam on the brakes while I am overtaking other vehicles in adjacent lanes, presumably because the software thinks the adjacent cars might be moving into my lane (they aren't).

As it stands, I really can't use cruise control at all without being seriously annoyed (and no doubt annoying the other cars around me), meaning my 2019 tesla has less automation than my 1989 honda accord had. I'm praying this is mostly due to my firmware version (2019.7.105) and the relative newness of HW3.

My thoughts exactly

 

[M3OC Rules]

I use TACC and autopilot pretty much every time I drive. I have phantom breaking occasionally because of people crossing a long ways ahead, overpasses, and incorrect speed limits. I know where the speed limits are wrong and verified they are coming from Google Maps. I don't use autopilot in those locations and use TACC by itself which isn't affected in my experience. I agree it's annoying and could potentially be dangerous but it's not so much that it stops me from using it all the time. I'm starting to think this is one of their biggest problems right now though. When you're driving its one thing but its especially bad for a passenger. I think it has really soured my wife on the car. We were just at a party with a couple with a Model 3 and they have the exact same situation. The guy drives the car and his wife doesn't want anything to do with it because of Autopilot and phantom breaking. Now this is what they tell other people when they talk about the car. Not the greatest sales pitch. And there are clearly people who drive the car regularly who are complaining here.

It seems like this should be a high priority at Tesla but it doesn't seem like it is. I would much rather have no phantom braking and accurate speed limit detection than NOA. I like watching the sausage get made but at some point I want to eat the sausage.

 

[mswlogo]

I use TACC and autopilot pretty much every time I drive. I have phantom breaking occasionally because of people crossing a long ways ahead, overpasses, and incorrect speed limits. I know where the speed limits are wrong and verified they are coming from Google Maps. I don't use autopilot in those locations and use TACC by itself which isn't affected in my experience. I agree it's annoying and could potentially be dangerous but it's not so much that it stops me from using it all the time. I'm starting to think this is one of their biggest problems right now though. When you're driving its one thing but its especially bad for a passenger. I think it has really soured my wife on the car. We were just at a party with a couple with a Model 3 and they have the exact same situation. The guy drives the car and his wife doesn't want anything to do with it because of Autopilot and phantom breaking. Now this is what they tell other people when they talk about the car. Not the greatest sales pitch. And there are clearly people who drive the car regularly who are complaining here.

It seems like this should be a high priority at Tesla but it doesn't seem like it is. I would much rather have no phantom braking and accurate speed limit detection than NOA. I like watching the sausage get made but at some point I want to eat the sausage.

TACC is where Phantom braking is coming from. It's the "Traffic Aware" part that has a head cold some days.

In my experience wrongs speeds, limited speeds and most "incidents" ahead are handled fairly smoothy.
When the system thinks it's gonna hit brick wall on the highway, it's pretty scary. It decelerates, out of no where, about as fast as my Performance can accelerate.

Occasionally a severe cutoff will hit brakes fairly hard too, but that in some cases is more or less correct, even thought it sometimes overreacted more than I would have.
If someone cuts you off and is accelerating away it sees that and doesn't slow down at all. Pretty impressive.

 

[Misanthropic Mike]

This morning it happened in a different spot, but I noticed that the nav map displayed my current section of road in red, indicating a traffic jam (there was no traffic jam, cars were flowing smoothly at about 75 mph). There might have been a jam there 15 minutes earlier and the map hadn't updated yet. Could it be that it initiates these slowdowns based on recent traffic information? Isn't that what the cameras and radar are for?

 

[mswlogo]

This morning it happened in a different spot, but I noticed that the nav map displayed my current section of road in red, indicating a traffic jam (there was no traffic jam, cars were flowing smoothly at about 75 mph). There might have been a jam there 15 minutes earlier and the map hadn't updated yet. Could it be that it initiates these slowdowns based on recent traffic information? Isn't that what the cameras and radar are for?

That's a great observation. I'll have to watch for that.

 

[Jay79]

Been happening to me more frequently since the new update, it sporadic though. Sometimes AP works flawlessly and sometimes not so much. It actually missed my exit last night on route to a supercharger. I was showing off to a girl I had in my car so I'm thinking my Tesla was getting jealous

 

[jsmay311]

In your TMC post you say it happens at a freeway interchange. TACC can temporarily reduce your set speed at interchanges even if the speed limit doesn't change. From the manual:

When enabled while on a highway interchange or off-ramp, Traffic-Aware Cruise Control may reduce your set speed in 5 mph (5 km/h) increments - to as slow as 25 mph (40 km/h) - to better match the reported speeds of other Tesla vehicles that have driven at that specific location. To override this and continue cruising at your set speed, tap the accelerator pedal or touch the plus (+) or minus (-) button on the touchscreen. The new set speed is maintained for the duration of the interchange or off-ramp (unless you override it or cancel Traffic-Aware Cruise Control). After the interchange or off-ramp, the set speed may revert or change as necessary based on the new location. For example, if you merged onto a different highway, the set speed reverts back to the set speed that was in use before driving on the interchange.

(1) It's not really that kind of an interchange. There are no curves anywhere near sharp enough to warrant a reduction in speed and no one slows down while driving through it.

Here's a map view of the section where the errors occur:

(2) More to the point, I drove through it again last night and paid close attention to the screen, and the speed limit sign on the screen actually disappears for a split second each time the set speed changes. So the problem it does appear to be driven by a problem with the speed limits, but it's apparently missing data rather than incorrect speed limits that are causing the problem.

I submitted a bug report at the time to report the problems with the speed limit.

But I still don't get why having no speed limit data for a very short section of highway should result in a change to the cruising set speed in TACC. And since it's a limited-access divided highway it shouldn't affect set speeds in AP either.

 

[M3OC Rules]

(1) It's not really that kind of an interchange. There are no curves anywhere near sharp enough to warrant a reduction in speed and no one slows down while driving through it.

Here's a map view of the section where the errors occur:
View attachment 26506

(2) More to the point, I drove through it again last night and paid close attention to the screen, and the speed limit sign on the screen actually disappears for a split second each time the set speed changes. So the problem it does appear to be driven by a problem with the speed limits, but it's apparently missing data rather than incorrect speed limits that are causing the problem.

I submitted a bug report at the time to report the problems with the speed limit.

But I still don't get why having no speed limit data for a very short section of highway should result in a change to the cruising set speed in TACC. And since it's a limited-access divided highway it shouldn't affect set speeds in AP either.

The data comes from Google. You can file a bug report to them.(Menu->Send Feedback) When you do that it makes you click on the section of road where the error is. I tried this on a long freeway entrance that is missing data just like your case. I found when I clicked on the section of road it was divided into like 15 sections on this entrance alone. They don't give you the speed limit info on the website so it's hard to know exactly what's even going on. They do have speed limits on the mobile app but only when driving at the location. I don't think they have fixed the one I sent in the bug report on yet. It's definitely sub-optimal.

 

[Misanthropic Mike]

Bear in mind that there is really no legitimate reason for TACC to initate uncommanded speed changes. As far as I'm aware, CC doesn't do this in any other vehicles.

 

[M3OC Rules]

Bear in mind that there is really no legitimate reason for TACC to initate uncommanded speed changes. As far as I'm aware, CC doesn't do this in any other vehicles.

They don't allow you to use autopilot more than 5 mph over the speed limit on city streets, etc. So when you transition to a road that is restricted it changes speed if it's more than 5mph over. This could be desirable if the map data was correct and will be required with FSD. TACC alone doesn't have the same restriction and I don't think it changes speed. Does it?

 

[Long Ranger]

TACC alone doesn't have the same restriction and I don't think it changes speed. Does it?

TACC alone doesn't change speed due to speed limit changes, but it will change speed temporarily if it determines that you are on a highway interchange or offramp. See my earlier post in this thread.

 

[jsmay311]

They don't allow you to use autopilot more than 5 mph over the speed limit on city streets, etc. So when you transition to a road that is restricted it changes speed if it's more than 5mph over. This could be desirable if the map data was correct and will be required with FSD. TACC alone doesn't have the same restriction and I don't think it changes speed. Does it?

In the example I posted about earlier, it did change the set speed while using TACC.

 

[M3OC Rules]

In your TMC post you say it happens at a freeway interchange. TACC can temporarily reduce your set speed at interchanges even if the speed limit doesn't change. From the manual:

When enabled while on a highway interchange or off-ramp, Traffic-Aware Cruise Control may reduce your set speed in 5 mph (5 km/h) increments - to as slow as 25 mph (40 km/h) - to better match the reported speeds of other Tesla vehicles that have driven at that specific location. To override this and continue cruising at your set speed, tap the accelerator pedal or touch the plus (+) or minus (-) button on the touchscreen. The new set speed is maintained for the duration of the interchange or off-ramp (unless you override it or cancel Traffic-Aware Cruise Control). After the interchange or off-ramp, the set speed may revert or change as necessary based on the new location. For example, if you merged onto a different highway, the set speed reverts back to the set speed that was in use before driving on the interchange.

It's interesting they have their own speed database. You'd think they could solve some of this missing map data with that. All I know is something needs to change or you're going to have self-driving cars going 30mph in areas where everyone else is going 60mph. That's unsafe and would make the passengers anxious to no end.

 

[Misanthropic Mike]

Let's not even get into the brand damage that is assuredly going on with Tesla cars constantly slamming on their brakes on busy freeways and causing dangerous traffic interruptions. People are going to be saying "I wouldn't be caught dead in one of those things". They need to fix this yesterday.

 

[Misanthropic Mike]

They don't allow you to use autopilot more than 5 mph over the speed limit on city streets, etc. So when you transition to a road that is restricted it changes speed if it's more than 5mph over. This could be desirable if the map data was correct and will be required with FSD. TACC alone doesn't have the same restriction and I don't think it changes speed. Does it?

It does do this on TACC alone, and it does it on the freeway, and it will often suddenly change the speed to 30 mph below the speed limit. It does it at seemingly arbitrary and random points along the road, apparently in response to recent or historical traffic jams. It isn't just in my area either, I took a trip down to Brooklyn over the weekend and it happened in CT, NY, MA, and NH. These aren't obscure roads either, this is out on I95, the east coast version of I5 for you California users.

 

[Mike]

First off, I really wish Tesla would offer just ordinary cruise control so that I don't have to continually monitor my speed while cruising on the highway, because the "active" cruise is unusable in it's current form. It randomly changes it's setpoint while I'm cruising on the freeway, making my car suddenly decelerate for no reason. It's not only annoying, it's dangerous. Today on the way to work it just suddenly changed from a setpoint of 73 mph to 30 and began braking hard. This happened in broad daylight and good weather when there were no other cars for several hundred yards in front of me (not that it'd be OK for it to do this in any conditions). As a separate issue, it will frequently (like perhaps once or twice per mile) slam on the brakes while I am overtaking other vehicles in adjacent lanes, presumably because the software thinks the adjacent cars might be moving into my lane (they aren't).

As it stands, I really can't use cruise control at all without being seriously annoyed (and no doubt annoying the other cars around me), meaning my 2019 tesla has less automation than my 1989 honda accord had. I'm praying this is mostly due to my firmware version (2019.7.105) and the relative newness of HW3.

I find manually passing slower traffic on my right will often cause a momentary speed drop if using NOA or plain TACC.

The target is always at my front right quadrant.

 

[SalisburySam]

Bear in mind that there is really no legitimate reason for TACC to initate uncommanded speed changes.

Yeah, there actually is, and my car on 16.2 does this very, very well. Example: driving North on I-85 to Piedmont Triad International (PTI) airport. Using TACC, NoAP, and everything else. On its own with confirmation from me by torquing the steering wheel, the vehicle automatically exits I-85 (70mph limit), reduces speed for the ramp, resets speed for the next Interstate (65mph), automatically exits to another Interstate and resets speed to 55mph, the limit on that road, then takes exit to the airport ramp, again decreasing speed to the new 45mph limit. Then NoAP disconnects leaving TACC and AutoSteer going. Pretty amazing to me as it all worked well and without moments of terror for me or surrounding drivers.

To recap, this was four uncommanded speed changes, all of which were necessary due to either safety (reducing ramp speed) or changes in legal speed limits. In my opinion, the car needs to handle this, and it does.

 

[Kimmo57]

Yeah, there actually is, and my car on 16.2 does this very, very well. Example: driving North on I-85 to Piedmont Triad International (PTI) airport. Using TACC, NoAP, and everything else. On its own with confirmation from me by torquing the steering wheel, the vehicle automatically exits I-85 (70mph limit), reduces speed for the ramp, resets speed for the next Interstate (65mph), automatically exits to another Interstate and resets speed to 55mph, the limit on that road, then takes exit to the airport ramp, again decreasing speed to the new 45mph limit. Then NoAP disconnects leaving TACC and AutoSteer going. Pretty amazing to me as it all worked well and without moments of terror for me or surrounding drivers.

To recap, this was four uncommanded speed changes, all of which were necessary due to either safety (reducing ramp speed) or changes in legal speed limits. In my opinion, the car needs to handle this, and it does.

Nice if it works. On my way to work the street has a 60 km/h speed limit, but the car thinks it's 80 and wants to speed up, so that's not so great. There should absolutely be a setting to turn it off.