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Rando-braking

Discussion in 'Autopilot & Autonomous/FSD' started by leedr74, Jan 4, 2020.

  1. leedr74

    leedr74 Member

    Joined:
    Dec 25, 2019
    Messages:
    8
    Location:
    Austin, TX
    I was cruising down I-35 from Austin to San Antonio and had TACC and AP running when all of the sudden the car just went to a halt!

    I luckily had it the pedal so the car behind me didn’t rear end me going 70!

    All in all things played out ok but geez did it truly scare me and the rest of the ride had me driving with anxiety.

    TIA, I’m running the latest update “7” in my M3 LR AWD.
     
  2. tvad

    tvad Member

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    Location:
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    Unexpected random braking and resulting anxiety is precisely why we don’t use TACC or AP.
     
    • Like x 5
  3. leedr74

    leedr74 Member

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    Dec 25, 2019
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    Location:
    Austin, TX
    Ok so it wasn’t my imagination then. Phew, relief for now...
     
  4. iwannam3

    iwannam3 Member

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    Location:
    Washington
    Seems to happen to me near shade from an overpass.
     
  5. JulienW

    JulienW Active Member

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    Location:
    Atlanta
    Just do a search for Phantom Braking. Also your car didn't "...just went to a halt!".:D
     
    • Like x 1
  6. lolder

    lolder Member

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    So it came to a halt which is a complete stop or did it briefly apply brakes and then resume? There's a big difference.
     
    • Like x 1
  7. ewoodrick

    ewoodrick Well-Known Member

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    Buford, GA
    Huge difference!
     
    • Like x 2
  8. JWSM3Owner

    JWSM3Owner Member

    Joined:
    Nov 19, 2019
    Messages:
    48
    Location:
    Virginia
    Just did a long road trip through Appalachia, about 95% of which was driven on AP/TACC. The car randomly/sharply braked for no reason in two situations: coming uphill towards an overpass (presumably the car mistook the stationary overpass for a stopped car) and when approaching an exit with construction/barriers where the road was also curving, so that again the car probably thought there was a stationary obstacle in the road. The car pretty much immediately started accelerating again, though; it was a disconcerting jolt, but the car never halted.
     
  9. dethman

    dethman Member

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    Location:
    socal
    yeah. one of those rando things that happens kinda frequently unfortunately.
     
  10. Not Sure

    Not Sure Member

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    Dec 12, 2019
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    Location:
    Transylvania
    Is that an underpass or a red fire-truck?
    I'm just not sure.
     
    • Funny x 2
    • Love x 1
  11. diezel_dave

    diezel_dave Member

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    Location:
    Utah
    This will probably happen to anyone who uses TACC/AP regularly. My theory is that many of these events that I have experienced are caused by inaccurate lane tagging of adjacent slower moving traffic. That is to say, my car misjudges cars in the next lane as being in my lane and thus slows down to match their speed. This happens most frequently when driving around a curve where it really struggles to determine which lanes the other cars are in.
     
    • Informative x 1
    • Like x 1
  12. afadeev

    afadeev Member

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    Location:
    NYC
    Yeah, it happens.
    One of many TACC / AP bugs.

    Eventually, you will learn when to expect them, and be prepared to over-ride erroneous AP behavior.

    All part and parcel of Tesla ownership.
     
    • Like x 1
  13. emmz0r

    emmz0r Senior Software Engineer

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    Location:
    Norway
    Watch the speed limit closely as well. I have had some major braking when the GPS speed data is inaccurate or when it is inaccurate position itself and gets the speed from neighboring off ramps etc
     
    • Informative x 1
  14. Gaelic123

    Gaelic123 New Member

    Joined:
    Jan 5, 2020
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    Location:
    Austin, Texas
    It has never happened to me.
     
  15. diezel_dave

    diezel_dave Member

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    Location:
    Utah
    You are one of the lucky few then. Make sure you never get complacent with the system because this can and will happen to you at some point in the future. It is just a matter of when.
     
  16. huangm777

    huangm777 Member

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    Nov 3, 2019
    Messages:
    132
    Location:
    Southern California
    It’s funny but phantom braking has rarely occurred for me. Then again I’ve only driven the car 1000 miles so I probably haven’t hit the conditions yet...

    What is interesting though is that the one time it did, it was on the exact stretch of highway that my Toyota Prius Prime would incorrectly activate the imminent crash warning. It was a curve on the HOV lane. Perhaps the tech is very similar after all...
     
  17. Ribeye67

    Ribeye67 I finally have a car that drives me.

    Joined:
    Oct 12, 2019
    Messages:
    14
    Location:
    Antioch, CA
    I have it happen on Highway 24 in number 4 lane when driving west from the Caldecott Tunnel near the Broadway offramp. speed limit suddenly shows 50 mph on the dash. I then accelerate until speed limit shows 65 again. Started turning AP off since getting off at next exit. AP is still great to have. It just needs work.
     

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