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First experience with TACC failure that almost caused an accident

nvx1977

Unknown Member
Nov 25, 2017
3,073
7,229
NH, MA
This morning, I was in bumper to bumper traffic when AP (TACC) did something completely wrong. From a stop, it began to accelerate toward a stationary truck right in front of me.

This was a wake-up call for me because I've been using EAP on this exact commute for over a year now, and TACC has never had trouble keeping pace with changing traffic speeds. Even on this drive, I had been following this truck in stop and go conditions for over 20 minutes with zero issues. Basically the truck comes to a stop, and I come to a stop. When truck goes, I start to go. Very routine. And then it happened. The truck stopped. I came to a stop. And then 5 seconds later, I started to go. But the truck had not moved an inch. I slammed on the brakes with about a foot of space remaining between us.

Now alert of the issue, I started to pay attention to the screen to see what the car was seeing. Sure enough, on the next stop, I see the truck disappear from the radar's view. And my car starts to accelerate again. I immediately brake. For the next mile or so, this would happen periodically. Sometimes when the truck disappeared from the radar's view, my car would not move forward. So there must be some failsafes in place. But clearly those failsafes are not robust enough.

By the time I pulled out my phone to try to catch this issue on video, TACC was starting to do better. I managed to capture one unintended acceleration by the car, but the truck comes back into radar view, and my car brakes before I had to intervene. You can see this incorrect acceleration at around the 1:03 mark. In my last year of using EAP/TACC, never once has my car move forward from a stop, even a little bit, unless the car in front starts to move first.

Several variables to consider here:
- it was raining, and that could have affected radar performance. But this was not an issue for most of the drive, and rain conditions were steady. I've also done the same drive thru rain countless times.
- I just got 2019.8.5, and I hear the AI has been revamped
- something about the truck could have been giving the radar difficulties (though it doesn't explain the flawless 20 min before the UA occurred). Notably, the radar couldn't see one car past the truck.
- something could have jammed the radar in the vicinity where these UAs were happening

Description has timestamp links to notable situations:

Bottom line: stay alert on AP/TACC and don't get complacent. It only takes the one glitch to cause an accident if you're not paying attention.
 
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Here's the moment the truck disappears.
A few observations:
The taillights merge with the cars in the two adjacent lanes (from the perspective of the autopilot cameras).
The black part of the truck is probably low enough that the computer ignores it or thinks it's a dark mark on the road.
The lift gate is about the same color as the road.
The top of the truck is about the same color as the sky.
Computer vision is really hard and that's why AP is in beta.
Screen Shot 2019-04-08 at 6.20.46 PM.png
 

woof

Fluffy Member
Supporting Member
Apr 30, 2009
1,602
2,060
Interesting...I had similar "incidents" with the BWM i3 MobilEye implementation. It just doesn't see dark trucks. Sometimes it does, and sometimes they just "disappear" like this one did for you. The i3 doesn't have radar to fall back on, however.

AI's are mysterious things.
 
I found AP has some issues in very slow traffic, like completely stopped for over 10 minutes, then move one car, then stopped again for 10 minutes and so on. After about 1 hour, it kind of freak out.

I was once in a completely jam using AP over 1 hour and while I am stopping, it suddenly went nuts with all alarms and red screen, ask me to take over immediately. However, I am not moving at all so I don't quite sure how to take over. Had to open the door and close it, which triggers something and it stopped. But I did not use AP for the rest of that trip.
 
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GolanB

Member
Supporting Member
Sep 22, 2018
620
743
NYC
Assuming you’ve submitted a bug report and provided the video to Tesla. Customer service will escalate this to the AutoPilot team for analysis and they should get back to you. This week they did a full analysis of a neighbors event and they’re looking into two radar failures on my case. For this to have happened I would imagine there are multiple failures happening here (perhaps radar proximity and visual detection failure).

Do keep us posted pls!
 

Alketi

Member
May 3, 2016
879
2,470
U.S.
From my read --

The truck is a tall wall-of-white in bad weather and not moving ... since every other lane around you was moving, the radar was fooled and started to ignore it.

Further, the camera NN didn't have a good identity on such a tall, close object.

@novox77 Bug report is good, but also report it through your account tools online and include the video link and description.
 
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nvx1977

Unknown Member
Nov 25, 2017
3,073
7,229
NH, MA
All of us can conjecture as to what may have happened but I’d be very interested to hear what Tesla had to say about this issue. It seems to be a very important issue in terms of safety so I wonder if it’s something you can follow up with through a service center since you have video and internal vehicle logs, etc?

I reported this to Tesla, both via the voice command "bug report" as well as through the form on my account page. Will post if/when I hear back.


An hour and 28 minutes to travel 32 miles? Ouch.

Travel times pretty much double whenever precipitation is a drizzle or more :(
 

GolanB

Member
Supporting Member
Sep 22, 2018
620
743
NYC
I reported this to Tesla, both via the voice command "bug report" as well as through the form on my account page. Will post if/when I hear back.




Travel times pretty much double whenever precipitation is a drizzle or more :(

My experience with Tesla recently is that you've got to stay on top of them when you've got an important issue. I haven't had much luck with prioritization through email or the online forms-- a call to CS, and a request for escalation seems to be the most efficient way of getting them engaged - especially on a safety issue.
 

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