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Tesla X slows down in cruise control

Discussion in 'Model X' started by Kiwimike, Jun 16, 2018.

  1. Kiwimike

    Kiwimike New Member

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    our Tesla slows dramatically in cruise control on the same road every time we drive along it.
    It’s a straight road with no obstacles either side.
    Anyone else had anything similar?
    Kiwimike
     
  2. buttershrimp

    buttershrimp Click my signature to Go Mad Max Mode

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    What speed does it change to? If it changes to the equivalent of 45 mph, then it's likely map data. It's why I look forward to speed limit sign reading in AP2.
     
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  3. Kiwimike

    Kiwimike New Member

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    We are in k/hr and it goes from 60k/hr to about 20k/ hr -
     
  4. hiroshiy

    hiroshiy Vendor

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    Hmm, 20km/h seems to be very slow. You mentioned there are no obstacles on either side but how about above? AP sometimes brakes if there's some overhead objects. Basically Tesla tries to whitelist such objects but there are places without such whitelists. For example in my 15 minutes drive into the central Tokyo I have about 30 overhead objects like signs, light poles, traffic sensors, DSRC transmitters, tunnels and over paths. AP braked a lot in early days but these days there are almost none.
     
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  5. LukasSwan

    LukasSwan Member

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    I had this happen in 2017 when I first got the car. Same as you. Then a software map update fixed it to my relief. I always had to predict it and override TACC by pressing on the accelerator pedal. Which is unsafe, annoying, and if I forgot made people behind me wonder "where are the jumping deer"?
     
  6. bob_p

    bob_p Active Member

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    We've seen AP/TACC slow down for several reasons:
    • A vehicle in front changes lanes to turn, causing your car to slow down and stay at a lower speed until the software decides the car in front is not coming back into your lane. The software appears to be too conservative, slowing down more than necessary and waiting longer than needed before resuming speed.
    • A false detection of an object in the roadway ahead causing the software to rapidly slow down before the software determines there isn't an object and resumes speed. This can happen if there's an object overhead or a rapid change in color (usually going from light to dark) in the roadway ahead. The software has been improving and has fewer false object detections than it had a year ago, but it still happens periodically. Like the first case, the software is taking a more conservation strategy, and slowing down until it can confirm things are safe ahead.
    • When operating under AutoSteer, if the software believes the speed limit drops below 50 MPH (in the US), the software can rapidly slow down. Since AP2 doesn't yet detect speed limit signs (as far as we know), this is caused by errors in the speed limit database.
    Rapidly slowing for no apparent reason can cause safety risks - vehicles behind aren't anticipating you to rapidly slow, which could cause a rear end collision (if the driver behind isn't paying attention) or, more likely, cause the driver behind to honk or respond to what seems to be your odd behavior.

    These situations were more frequent a year ago with AP2 - and continue to improve with new software releases.
     
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  7. DCGOO

    DCGOO Member

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    My S does this, typically because it sees a "school zone" speed limit sign. These are supposed to only apply for a short distance, but typically i have to wait until the car sees a regular speed limit sign returning to the normal speed limit. Often these do not exist, so I am stuck with lower limit. Annoying, but adjustable with the accelerator "Damn, I have to drive again?". First world problem LOL.
     
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  8. _jmk

    _jmk Member

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    I noticed today that it slowed down on cruise when I was approaching a turn 'too fast'. Never have had this before, I'm on 21.9.
     
  9. BigMskiman

    BigMskiman Member

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    If I'm going about right speed, my car does not slow during turns, but too fast and it knows to slow down. It's great.
    But I'm not seeing slowing as I approach a turn, only while into it.

    old |v2018.18.2|AP2,PUP|
    new |v2018.21.9|AP2,PUP|
     
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  10. boaterva

    boaterva Supporting Member

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    Remember, it doesn’t ‘see’ anything yet. Maybe you know this, but let’s not say it does when it doesn’t. :D

    I get this also, I’m in some area where you get the dreaded ‘speed restricted to 40 MPH’. F that, I want to go 50 like everyone else is! :cool:
     
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  11. DCGOO

    DCGOO Member

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    It sees and reads the speed limit signs, that is what I was referring to.
     
  12. XHabjab

    XHabjab Helping to end the ICE Age

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    As of June 2018, there are no Teslas in the wild that 'read' any signs.

    Maybe on closed track on Tesla property, but not yours. No.
     
  13. boaterva

    boaterva Supporting Member

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    No, it does not. The cars do not see anything. It does NOT read speed limit signs. It’s reading a GPS-based database.
     
  14. toonman

    toonman Member

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    I was on a 300+ miles road trip last weekend and this happened to me. Was on autopilot and all of a sudden, it slows down (hard brake) significantly (from 70mph to about 50mph) before I stepped on the accelarator again. Freaked everyone in the car. Luckily no one was behind. And the road ahead was clear. One think I noticed on the second occurrence is we are going down slope and it happens when the road ahead was a transition between a down slope and an up slope.
     
  15. XHabjab

    XHabjab Helping to end the ICE Age

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    I have noticed this in several places where a road was recently under serious construction, including rerouting of the road with a detour and maybe flagmen. The construction is now finished and the road in good shape but the GPS data still shows construction, and a 45 mph (or similar) zone.

    An example of this is on I-35 near Salado TX.

    Also Hwy 290 near Hockley TX. (Maybe fixed now?)

    There are several others that I'll remember later.

    I've learned to turn off CC in these busy areas lest I get rear ended.

    If you experience this by the way, you can document the exact location to the Garmin folks and a map update will occur, based on your input. The web page is at
    Garmin | Report a Map Error

    Check the box that says "no device, map only", leave device blank, for "what map are you using", select "Other" (very last choice in the long list), enter "Tesla" in the "Other" field.

    Garmin does the maps for Tesla.
     
  16. SKRGO

    SKRGO Member

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    ******************************************

    Yes, Garmin does the maps.

    But "TOMTOM" handles the speed data that Tesla uses.

    Please read past posts on the subject.

    Speed limit info is comically bad on AP2 / AP2.5, possible to update?

    I too have the same problem on many roads that I drive on.

    I wish Tesla owners could all input GPS Lat&Long with street name or number into a spreadsheet, then post/email that info to the TomTom data error link.
     
  17. vandacca

    vandacca ReActive Member

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    AP1 vehicles actually do "see" and read speed-limit signs. Not sure what's taking so long for AP2 vehicles.
     
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  18. Peteski

    Peteski Active Member

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    Mine does this too, but it only works for certain corners and on approach to some junctions/roundabouts. It's a bit or miss at best, but quite a promising feature once developed further. I guess it must be building a database of max road speeds to apply to specific corners or making some on-the-fly calculation based on the GPS mapping data. I expect the former otherwise as it totally ignores some corners and junctions!
     
  19. mongo

    mongo Well-Known Member

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    I think you mean it doesn't 'read' anything. It does see lane lines. ;)
     
  20. boaterva

    boaterva Supporting Member

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    The context was speed limit signs. I was quoting from the original, also.

    It obviously recognizes lane lines. Or we would have some other discussions going on. :D
     
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