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TACC with 7.0 - unexpected slowdowns

mwulff

Member
Jan 15, 2015
348
25
Danmark
Hi everybody.

I just updated my Model S to the 7.0 firmware and everything works fine. There is however a small glitch that has me wondering about the new tacc.

Here is the situation:

I am driving along on a clear almost straight road at 70 km/h. No cars in front of me but suddenly my Model S starts slowing down and eventually drops to 50-55 km/h and after 100-120 meters it speeds up again.

This happens several times along this particular road. Now this road is newly built and I know for a fact that it is not in the cars Navigon maps. Google maps knows about this road but the navigon system does not. I suspect that the tacc thinks that it is on an older road that has been replaced and slows down according to the old roads.

Has anybody else experienced this behaviour? I have sent notes to tesla at every incident and intend to keep doing this. But it is really dangerous to have the car slow down for no reason what so ever.

This is the road I am driving: Google Maps

UPDATE: As requested here is a video of our car being driven on this particular road, at the beginning it is incorrectly stated that Autopilot is engaged, only the traffic aware cruise control was engaged:

 
Last edited by a moderator:

blanche

Member
Jun 30, 2015
100
8
Leesburg, Virginia
Happened to me exactly once so far. Last week I was driving with TACC + AP set to 70 (speed limit 65) on the Northbound 495 (beltway) express lanes in Fairfax, VA. I drive this road every single day, but for some bizarre reason I noticed the car decelerating even though there wasn't anyone ahead or behind me. Weather was sunny, clear and nothing on the well marked road. Fortunately, I didn't inconvenience anyone else. When the speed hit 55 and kept decelerating, I disabled and re-enabled TACC and everything was good ever since. No warning signals came on.

No change on the road itself in years. Exact same road I have been driving for a few years now. I don't think the express lanes are in the GPS (not entirely sure), but AP works great (since day one) on the express lanes so I'm quite puzzled by this behavior.
 

mwulff

Member
Jan 15, 2015
348
25
Danmark
I should add that I have tested this several times and the slow downs happen at the exact same places every time leading me to believe that it is checking the navigon maps.
 

!S4

Member
May 31, 2015
89
3
Chicagoland
I've had the same situation and can reproduce it pretty easily. It happens to me on overpasses. One is a new overpass which isn't even on the GPS map yet. My theory is that it speeds back up after it has crossed all the lanes of the road beneath.

Location 1:
Google Maps

Location 2:
Google Maps
 

Discoducky

P100DL, 2021 M3, 3 CT reservations and counting
Dec 25, 2011
3,557
4,616
My mountain
The tacc worked perfectly on that road before the 7.0 update.

If you can safely take a video of the section it would be much easier to diagnose.

Is it happening anywhere else? How many miles have you put on the car so far and is it connected to WiFi at home?
 

mwulff

Member
Jan 15, 2015
348
25
Danmark
I could shoot a video safely. I will do so as soon as possible. But I have 20.000 km on the car and the tacc used to work perfectly on this particular road. My wife drives it every day on this road.

So the problem is really a new one with 7.0. Until Saturday the tacc worked perfectly.
 

DDotJ

Member
Feb 28, 2013
753
1,227
California
Happens to me with autosteer as well, as I go down the 55 NB passing under the 5. Happens at the same spot all the time. The car starts to slow down and then picks up speed again after I pass under the bridge.
 

mwulff

Member
Jan 15, 2015
348
25
Danmark
Video is on the way, uploading right now. I think this is actually a quite serious issue with the firmware. The amount of braking applied is quite a lot. From 70 kph down 38 kph. Thats dangerous in close traffic.
 

greensprit

Member
Dec 7, 2013
11
1
Boston
I've had this happen a couple of times as well, it seems to react to particular shapes of shadows on the road. When TACC first came it it seemed to rely primarily on the radar and would not slow down for stopped vehicle. Then, over time they started to incorporate more camera usage and now it will pick up a stopped vehicle, bit it also seems to have some false positives with shadows. Overall, I think it's better this way then it was when it first came out. It keeps improving though, i'm sure these false alarms will be mitigated with some fleet learning.
 

ddimit

Member
Do you have Autopilot on? only thing i can think that would slow you down if it prompts you to grab the wheel and you don't the car will being to slow down until it detects wheel motion from the driver. you should have all kinds of alerts before hand if this is the case
 

mwulff

Member
Jan 15, 2015
348
25
Danmark
These are not false alarms. This road has worked perfectly until 7.0 and now is just weird. We have never before encountered problems on this particular road and we drive along this bridge at least twice a day.

We did not engange the autopilot on our test runs because we didn't want it to interfere with the test of the TACC.

But the video is now available, I added it to the first post as well.

 
Last edited by a moderator:

LetsGoFast

Active Member
Oct 13, 2014
1,329
101
Virginia
That appears to be a bug. I bet this is an artifact of the new GPS enabled TACC/Autopilot. It apparently uses the GPS to determine when it should reduce speed for sharp curves. As you mentioned, it is missing GPS data for that particular road and I bet that introduced this bug. I would submit a bug report to Tesla and hopefully they will update it with an incremental Autopilot "learning" update.

It wasn't completely clear on the video. Is there a missing map segment in every one of the locations where you have this problem?

As an aside, it is interesting that you refer to GPS satnav as "Navigon" as a standard. I didn't realize that they were so dominant in Europe that it became the generic word.
 

S4WRXTTCS

Well-Known Member
May 3, 2015
5,467
6,224
Snohomish, WA
I really wish Tesla would give us some kind of diagnostic screen to let us know what in the world it's doing sometimes.

There have been reports that the TACC slows down for corners so maybe it's expecting a corner.
 

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