TACC does not work very well on curvy roads :(

Torpedo Ted · Mar 31, 2015

I know TACC is probably designed for american highways, but I expected it to also work well on most "major" roads. In my case, the main road between two of the biggest cities in Norway.

Very often when the car in front of me enters a curve, the car aparantly loses track of it and disengages TACC. This has some annoying and potentially dangerous results...

When it disengages TACC, it will start to speed up since cruise is still engaged, and right after the curve it will detect the car in front and quickly slow down. Resulting in a, well, not very smooth ride...

I also had one potentially dangerous situation: It disengaged TACC when the car in front turned, my car increased the speed since cruise was still on. While my car was accellerating towards the car in front, the car in front had slowed down entering another curve. Resulting in my car going way too fast, and detecting the car in front very late. It started to slowly brake (not enough!), and then suddenly, without warning it just deactivated TACC/cruise! I had to quickly step in and brake myself.

The problem is obviously that the car only looks straight forward when following a car. It should be able to detect that the car in front enters a curve, and then watch to the side instead. Especially when you are entering the curve yourself - it should understand that there's no point in looking straight foward, when you are turning the steering wheel.

I should probably rather report this to Tesla instead of posting it here, but I don't know where I can give Tesla feedback.

brianman · Mar 31, 2015

Torpedo Ted said:
I should probably rather report this to Tesla instead of posting it here, but I don't know where I can give Tesla feedback.

1. Use the voice feature in the car, starting with "Bug Report". Note that you'll want to make your report fairly brief (think answering machine with a time limit) for better reliability in having the report accepted by the car.
2. Send mail to ownership at teslamotors.com

pgiralt · Mar 31, 2015

You can find contact numbers for Tesla here:

Contact | Tesla Motors

I'd post the number I see, but it's a North America number. It should show you a different number when you reach that page from Norway. Definitely report it to Tesla.

- - - Updated - - -

brianman said:
2. Send mail to ownership at teslamotors.com

I thought that email address no longer works.

brianman · Mar 31, 2015

brianman said:
2. Send mail to ownership at teslamotors.com

pgiralt said:
I thought that email address no longer works.

It worked as of Sept 16, 2014. I haven't tried since then.

rneugebauer · Mar 31, 2015

My Tesla will only arrive later this month, so my TACC experience is limited to the test drive.

But it I do have > 12 years of experience with Mercedes Distronic, which has the same overall functionality.

What at I can tell you is that there are situations in which TACC cannot work as you expect, and roads with strong curves are one of them.

You our day the car should react to you turning the wheel, but in reality the car in front disappears out of the system's sight when it enters the curve and you're still going straight. In very strong curves, unless you're tailgating, it may literally be out of sight for moments, you know it's still there, but the car doesn't.

Be be prepared to take over in curves where TACC starts behaving like you describe. It will not learn, nor will it improve with time.

Mercedes' solution for curves is to slow down and/or not accelerate while you're steering a curve, which can be annoying too, when the car in front accelerates and you want to, too.

Other situations to be aware of:

Up and down roads: The radar beam is not only narrow sideways but also up/down: it can be that your car is on a slight hill and the beam doesn't see the car in front as the beam goes above it. It eventually sees it as you get closer, but it may lead to harder braking that you like.

And then, all the situations where the human sees the light go red and knows it's pointless to accelerate to catch up with the car in front but at at distance, where you see pedestrians approaching and know you'll have to slow down.

Distronic and TACC are not full autopilots, but they can be s great help if used right.

jerry33 · Mar 31, 2015

brianman said:
It worked as of Sept 16, 2014. I haven't tried since then.

It doesn't work anymore, but you'll get a bounce with the correct email address. I don't know what that is for Norway though.

brianman · Mar 31, 2015

rneugebauer said:
Be be prepared to take over in curves where TACC starts behaving like you describe. It will not learn, nor will it improve with time.

Mercedes' solution for curves is to slow down and/or not accelerate while you're steering a curve, which can be annoying too, when the car in front accelerates and you want to, too.

I'm a bit confused. I'm not expecting the car to "learn" (yet

) but I'm surprised you're asserting that it won't "improve with time" despite Tesla's history of and commitment to software updates. Heck, you've offered the Mercedes example of a solution to the problem and are assuming Tesla won't at least meet that standard. Odd.

CHG-ON · Mar 31, 2015

I use TACC all the time and absolutely love it. But I keep in mind that it is simply a convenience and I MUST stay totally engaged while driving. So my foot is always at the ready either for acceleration or for brake. I have found that when I am following at 3 or 4, it does a better job at tracking a car around a bend (not a corner). But I have moved to 6-7 for peace of mind and I now find that it loses the car much more easily. One thing I really like is that it is quite easy and smooth to either hit the go pedal or the brake when needed and there is no drama to it. When I'm done overriding it, TACC simply takes over again. I rarely have to disengage it. However, I always do disengage when I approach an intersection or where there are suddenly a lot more cars or other activity going on. It took me about a week to get accustomed to it and it's way of perceiving what is in front of me. But I seem to be able to use it pretty seamlessly. I do live in more rural/suburban area, rather than a densely populated area. So that might be why I find easy to use. I am not often in heavy traffic with lots of things going on in the periphery. I think that helps.

I have no problems with a car moving into another lane or somebody cutting in front of me. It reacts instantly to the new car, tracking it and adjusting speed accordingly. And that's before the 6.2 update, which I installed last night.

Stoneymonster · Mar 31, 2015

I just used it on highway 17 from Santa Cruz to Los Gatos and it worked flawlessy the whole way, zero intervention from me. Medium heavy traffic, lots of weaving idiots, on a very curvy road, short wall to the left with oncoming traffic. Car distance set to 6 or 7. Starting to wonder if the poor performance people are experiencing is when the following distance is < 6.

ecarfan · Mar 31, 2015

Wow, Hwy 17 seems like a pretty challenging road for TACC, I am impressed that it worked so well for you.

Stoneymonster · Mar 31, 2015

ecarfan said:
Wow, Hwy 17 seems like a pretty challenging road for TACC, I am impressed that it worked so well for you.

I was actually extremely surprised, myself.

Tuan · Mar 31, 2015

I have to say that TACC has been working well for me as well in most occasions. However there was one occasion that the road was quite curved and the TACC did not engage and slow my car down until the car in front me was half way into my lane. The road was curving left and I was on the left lane. The car on the right lane was changing lane from the right onto my lane. I saw the car cutting in front of me so I was about to react and step on the brake, but I wanted to see how long before TACC would detect the car and slow down. TACC distance setting was on 5.

The point is that TACC is working surprisingly well, but there's room for improvement for a smoother ride.

billarnett · Apr 1, 2015

ecarfan said:
Wow, Hwy 17 seems like a pretty challenging road for TACC, I am impressed that it worked so well for you.

?? 17 is a FREEWAY. I certainly expect it to work there. I find it works well enough most of the time on real lay twisty roads (think Skyline Dr or Woodside Rd west of Woodside).

Stoneymonster · Apr 1, 2015

billarnett said:
?? 17 is a FREEWAY. I certainly expect it to work there. I find it works well enough most of the time on real lay twisty roads (think Skyline Dr or Woodside Rd west of Woodside).

I guess on anything with more curves than 17, I question the use of TACC. I mean, Tesla has always almost explicitly said TACC and autopilot are intended for highways.

Kipernicus · Apr 1, 2015

Does TACC adjust itself when it sees new speed limit signs? How about those other signs that show Curve Ahead and recommend a speed? They look different from the speed limit signs.

Stoneymonster · Apr 1, 2015

Kipernicus said:
Does TACC adjust itself when it sees new speed limit signs? How about those other signs that show Curve Ahead and recommend a speed? They look different from the speed limit signs.

No, TACC does not adjust based on speed limit, though you can manually reset the TACC speed to the new limit. My car also has not read the curve speed signs, and it misinterprets speed-limit signs that say "trucks-only" as applying to it, so I wouldn't want TACC to auto-adjust right now.

stevezzzz · Apr 1, 2015

Yesterday was my first day with 6.2 firmware. I was driving on a moderately curvy road, with TACC engaged and locked onto the car in front of me. I noted as the car in front started into a turn that TACC lost its tracking lock for a few seconds. My car didn't accelerate, but that may have been just a happy accident of the TACC set speed matching the car's current speed. Darn it, I guess more experimentation is required... :biggrin:

Barry · Apr 1, 2015

It seems to me that some people are using cruise control where it shouldn't really be used.

Stoneymonster · Apr 1, 2015

Barry said:
It seems to me that some people are using cruise control where it shouldn't really be used.

I agree, but it's nice to know the limits.

stevezzzz · Apr 1, 2015

Barry said:
It seems to me that some people are using cruise control where it shouldn't really be used.

Oh, I don't know: I use TACC most of the time, even when I know it's likely to screw up. Keeping an eye on TACC and trying to fathom its limitations keeps my mind in the game. :biggrin:

TACC does not work very well on curvy roads :(

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