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Autopilot-to-TACC (autopilot cancel) bad interaction

Discussion in 'Model S' started by tls, Jul 7, 2016.

  1. tls

    tls Member

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    I wonder what others here think about what happens when cancelling autopilot while speed restricted on a non-divided highway.

    Example:
    1. I am traveling at 60MPH with autopilot engaged on a 2-lane road.
    2. I enter a 40MPH zone as I pass through a small residential area, and the car displays the speed-restricted message as it slows to 45MPH.
    3. I turn the wheel to avoid a road surface defect (e.g. pothole) or because Autopilot deals poorly with a sharp curve.
    4. The car leaves autopilot but remains in TACC mode, and accelerates to the full 60MPH speed that was set in step 1.
    I understand why this happens -- because there is no speed restriction for pure TACC, but there is one for autopilot -- but this strikes me as a very, very bad interaction of the speed-restriction and TACC features. The car should, I believe, never accelerate automatically when a driver assistance feature is disengaged.

    It needs to retain a little more state: when it transitions from a speed-restricted autopilot condition into TACC-only, it needs to reset the TACC speed to the restricted speed. Anything else can cause acceleration that from the driver's point of view is sudden and unexpected -- and that's not good.

    Do others agree?

    Note that though one can train oneself to always cancel autopilot with the brake rather than the steering -- and I am a staunch advocate that autopilot-assisted driving is a skill that itself requires the driver to learn and practice a number of new habits for safety, this among them -- it is also possible to cancel autopilot accidentally by bumping or too firmly nudging the wheel.

    I don't know whether this interaction also happens in the case of the flashing red "TAKE OVER IMMEDIATELY" e.g. when autopilot loses the lane line on a sharp curve. If it does, that'd be particularly bad. There's a section of road near here where the speed limit drops from 55 (straight as an arrow, too) to 30 with a series of very sharp curves where autopilot frequently requires a driver takeover. I never let autopilot enter that area without manually reducing the set speed precisely because I'm worried about this interaction; but I live here, so I know! A driver from another area could be surprised.
     
    • Informative x 4
  2. kavyboy

    kavyboy Member

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    Agreed. This would be the one thing I would consider a defect in AP/TACC. I can think of no use case where breaking AP should result in acceleration. Disengaging AP implies that the driver thinks that the current conditions have become too complex for AP to handle. Adding additional complexity into the scenario by accelerating makes no sense. Disengaging AP should disengage TACC too, in my opinion.
     
  3. mikeash

    mikeash Active Member

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    I think you're totally right. I've never had a problem with this and don't imagine I will, as I'm always mindful of what state the car is in, and am ready with the brake (and the car accelerates pretty gently on its own). But still, it's a great point and there's certainly some room for error, and the change you describe would help.

    I'm pretty sure that "TAKE OVER IMMEDIATELY" would not suffer from this, as that doesn't actually disengage autosteer. It just stops the car if you don't take over promptly.
     
  4. tls

    tls Member

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    Actually, I think it probably does (not super eager to provoke TOI as a test, however). When it tells me to TAKE OVER IMMEDIATELY, I do. But if I did so by turning the wheel to correct the car's line rather than tapping the brake *and* turning the wheel, I'd be in exactly the situation we're talking about here, right? I'd have cancelled the auto steering and the car would promptly accelerate from the restricted speed (35MPH on the section of road I have in mind) to 60MPH or more. Not good. Or am I thinking about this wrong?
     
  5. mikeash

    mikeash Active Member

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    Yes, I think that TAKE OVER IMMEDIATELY wouldn't disengage, but if you started turning the wheel you would. But it's been a while since I experimented with it, and I didn't do a whole lot, so I could be wrong. Either way, the effect is pretty much the same.
     
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  6. SomeJoe7777

    SomeJoe7777 Marginally-Known Member

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    I completely agree with your analysis and believe you're correct that the TACC set speed should be reset to the autopilot restricted speed.

    I have a related complaint about AP in a similar situation:
    • Using AP on the freeway in congested traffic, going at or slightly below the speed limit (55 MPH). TACC set speed is 60 MPH.
    • Traffic becomes quite congested and slows to 15 MPH. This is slow enough that AP begins using the car in front for guidance instead of lane lines.
    • Car in front is quite a ways back from the car in front of him, and then changes lanes.
    • AP tries to follow the car in front as he changes lanes, so I hold the wheel, disengaging AP but not TACC.
    • There is now a big gap to the next car and my TACC set speed is 60 MPH so I get a giant acceleration.

    I feel that if the car's actual speed is more than 25 MPH below the TACC set speed, then disengaging AP by moving the steering wheel should disengage TACC as well to prevent this situation.


    While we're at it, I'd recommend some other user interface enhancements:
    • Using blue for the TACC-engaged indicator is inconsistent with all other vehicles when in TACC-only mode. It should be green in TACC-only mode and blue (along with AP steering wheel icon and lane lines) in autosteer mode. The color indicator lets you know at a glance what mode you're in.
    • TACC should have its own engaged/disengaged chime (different from, and in addition to autosteer) to give you audible feedback that TACC is engaged or disengaged.
    Not maintaining in your head what mode you're in (manual, TACC-only, or TACC+autosteer) is one of the root causes of some of these incidents. The car needs to help the driver stay clearly informed of the current driving mode.
     
    • Like x 3
  7. kavyboy

    kavyboy Member

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    I thought the rainbow road Easter egg was good for this. It just needs to be toned down a lot.

    I've had the same thought. Just a triple chime instead of the normal double would be all I need.
     
  8. chillaban

    chillaban Member

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    If you haven't yet, please do communicate this feedback to Service. I completely agree with you that this behavior is unintuitive. Seems like when AP cancels and transitions to TACC in a restricted zone, TACC should set the restricted speed.
     
    • Like x 1
  9. brkaus

    brkaus Member

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    I've communicated the color of the indicator several times. It's a problem for colorblind people. Hoping 8.0 addresses it, but otherwise only response is that request was forwarded.

    Agree with other resume related concerns.
     
  10. jmsurpri

    jmsurpri Member

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    This gets me every time in a slightly different way. I'll cancel AutoSteer and resume driving manually, forgetting TACC is still on. When I lift off the accelerator to regen for a stop, car maintains TACC speed which takes me by surprise and I have to hit the brakes to start slowing down. I almost want TACC+AS to be locked together. When either is disabled for some reason, both should be disabled.
     
  11. brkaus

    brkaus Member

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    It does feel like any "cancel" should bring the default state all the way back to no driver assistance of any kind.

    Regen would make it clear that auto assist mode was cancelled.
     
  12. Saghost

    Saghost Active Member

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    Disagree with this - there are certainly times where having TACC without auto steer is useful, I wouldn't want to be unable to have that.
     
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  13. brkaus

    brkaus Member

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    Agree that both should exist by themselves. It's just on cancel, the least ambiguous answer would to to turn off both. Rather than treat lane keeping and tacc separate.
     
  14. mikeash

    mikeash Active Member

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    In short, turn off TACC if you override Autosteer.

    I'm not sure what I think about that. On one hand, it does seem wise. On the other hand, sometimes I override Autosteer just because it became stupid and started heading for the next lane, and I just want to bring it back in line without affecting speed. If it started slowing down when I overrode the steering, that would be a little annoying. I'm not sure which aspect is more important....
     
  15. Saghost

    Saghost Active Member

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    Tesla gave you both options... If you tap the brake or push the lever away from you, both drop. If you push the steering, only AutoSteer drops. This seems to make sense to me - we just need to train our choices to match what we want from the car.
     
  16. jmsurpri

    jmsurpri Member

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    Yeah there are definitely pros and cons. I agree on the highway you don't want regen to kick in. From a symmetry perspective, you can't enable AS without TACC, but you can disable AS by itself. I think that's one problem in that I think of AS as the set TACC+AS. If we had the option to just enable AS without TACC, it might be easier to treat them as separate functions.
     
  17. ifonul

    ifonul Member

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    Totally agree with this! In my case, I use AS+TACC at +5mph (70mph), but the actual HWY speed is say 55mph. Now, if I want to exit, the natural tendency is to grab the steering wheel and exit, which in turn disables AS, but not TACC, which makes me try to take the exit at 70mph with no cars in front. Fun, but totally unsafe :) There should be at least an *option* to 'link' AS and TACC when disabling AS.
     
  18. eddiemac

    eddiemac Member

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    IMO, if you tap the brake, it's because you want to take over and it should cancel both. Same for taking over the steering, it should disable both. If you want to disable only autosteer, pushing the lever would be a natural way to do it.
     
  19. Saghost

    Saghost Active Member

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    I agree on the brake tap, but not the other two.

    Grabbing the steering indicates you want the car to go somewhere else (whether because AP is wrong or because you changed you mind,) but doesn't say anything about speed - and I would be annoyed if TACC dropped every time I corrected AP mistakes.

    The lever is the TACC lever to begin with, so pushing the lever to disable should certainly disable TACC - and at the moment you can't have autosteering without TACC, so it disables both.
     
  20. S4WRXTTCS

    S4WRXTTCS Active Member

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    I've never experienced this because I don't use AP on speed restricted roads.

    But, I definitely agree that if this is it's behavior then it needs to change. The new AP derived speed needs to be the set speed for TACC, until you change it.

    Have you sent Tesla an email? To me it's simply something they overlooked.
     

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