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Model S Autopilot random braking on empty freeway (2019.28.3.1)

Model S Autopilot random braking on empty freeway (2019.28.3.1)

2017 90D - 2019.28.3.1 (FSD purchased)

I made a round trip trek from Dallas to Austin on Thursday. I drove during the day going down and used the TACC when traffic allowed. I drove back home in the middle of the night with sparse traffic, so I trusted Autopilot (with Navigation On Autopilot engaged).

Several times on the way home, the autopilot drastically dropped speed from 75MPH (speed limit) down to 40MPH. This was on an established freeway. There was no road construction. The lane lines were visible. No other traffic (thank goodness). I did notice the speed limit sign on the dash go from 75 to 40. I'm not sure why. It changed back to 75 in less than a second.

I've done this same trip with previous firmware and didn't have this issue. I did a bug report each time.

Question: do I need to call Tesla and have them pull the logs or will the bug report be enough?

I feel like it is a firmware issue, but if anyone has another thought I would be interested in constructive discussion.

murphyS90D | August 24, 2019

Speed limit comes from the map provider on AP2 cars. The place where the limit dropped to 40 was probably a construction zone in the recent past. Until the map gets "fixed" there is nothing that you can do.

The map in my AP1 car hasn't been updated for over a year. They tried recently but the updated failed and wasted 15 GB of my WiFi allowance in multiple tries. Fortunately an AP1 car knows how to read speed limit signs.

EVRider | August 24, 2019

You said you “used the TACC when traffic allowed” — you can use TACC regardless of the traffic volume, so I wonder what you meant by that.