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TACC rough in stop-and-go traffic

Discussion in 'Model S: Driving Dynamics' started by DSTAR, May 20, 2016.

  1. DSTAR

    DSTAR Member

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    Model S 90D, 2016, pre-updates.

    I love TACC and Auto-pilot, use these features a ton, and appreciate them no end in highway slow crawl and stop-and go. Typically the experience is buttery-smooth.

    A couple of days ago I was in a really bad stop-and-go stint in Fremont, CA, not on a highway. Exceptionally slow, frequent full stops. And TACC felt very jerky for a couple of miles (which translated to well over 20 minutes). It felt like the car would start breaking too late, then the sensation was as if the front would break a split-second before the rear... just a bit odd and rough. Once on the highway, 680 north in a slow crawl... back to buttery smooth.

    Anyone else have this experience?
     
  2. jmsurpri

    jmsurpri Member

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    Were you on TACC *and* AutoSteer? I've done my work commute in TACC-only and TACC+AutoSteer. It's mostly stop and go city driving. I've found that TACC-only brakes much more smoothly than TACC+AutoSteer. It seems to track the car in front perfectly, matching it's speed and deceleration. TACC+AutoSteer is very jerky in comparison, always stopping too late and abruptly.

    My running theory is that the two systems are using different sets of inputs. TACC only tracks the car in front and doesn't worry about lane keeping. TACC+AutoSteer tracks both car in front and lane markings. With stop-n-go city traffic and badly marked roads, AutoSteer is constantly switching from tracking the car and tracking the lanes. I have a feeling this switching causes some algorithmic delay, resulting in late braking. Ie, when switching from one to the other, the system needs a few frames of reference with the new inputs before figuring out the environment. This is less a problem on highways with clearly marked dividers.
     
  3. DSTAR

    DSTAR Member

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    That could be it. I was in TACC+AutoSteer.
     
  4. docgarner

    docgarner Member

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    Also, consider the follow proximity setting ( the left stalk twist adjustable that goes from 1-7 ). It gets a lot smoother with a higher number. I keep mine at 5 for this very reason.
     
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  5. chillaban

    chillaban Member

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    That's what I found on my test drive. The Tesla settings of 1 and 2 are extremely aggressive and much akin to an aggressive human driver. When TACC/AutoSteer are in control, you are a passenger, and that's probably how passengers feel when you are driving that aggressively as well.

    I found that the 3 setting was pretty acceptable in California stop and go traffic in terms of following at a reasonable distance yet not giving you a heart attack in those California traffic waves that go between 60mph and full stop.
     
  6. DSTAR

    DSTAR Member

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    Thank you! I will definitely try using a higher number... I typically keep it on 1-2 depending on conditions :)
     
  7. RDoc

    RDoc S85D

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    The problem with high values for following distance is other drivers cutting in. I'd like a .75 or .66 setting.
     
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  8. ecarfan

    ecarfan Well-Known Member

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    I don't trust TACC on anything less than 6. (Yes, I know my 2013 S doesn't have AP, but I've spent a few hours driving my dad's 2015 S in AP mode. It's fun :)
     
  9. kort677

    kort677 Active Member

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    I haven't seen any issues, I keep mine on 1 or 2
     
  10. Topher

    Topher Energy Curmudgeon

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    Why do you care about other cars cutting in? They make you what, 20 seconds later? If you leave a bit of room ALL the traffic will be smoother and (if enough people do it) you will get where you are going quicker. See: traffic wave analysis.

    Thank you kindly.
     
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  11. chillaban

    chillaban Member

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    I can tell you from 3 years experience of driving in California with another TACC system that on a 30 minute drive with a relaxed following distance, over 50 cars attempt to cut in if you consistently leave 2 car distances in front of you. Even the Google self driving cars admit they had to program the car to take some risk otherwise it can get stuck in a situation where it makes very little forward progress against a barrage of drivers taking advantage of it.


    And yes we understand it's risky and hope other drivers understand the following distance we are leaving is for safety and not an invitation to cheat the queue. No luck in getting people to understand that in my 6 years of driving around here.
     
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  12. kort677

    kort677 Active Member

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    I would bet that you don't do a lot of congested urban driving.
    leaving too much room between cars causes many other issues.
    there is a fine line between being a proactive driver and an overly aggressive driver, being too passive in that environment is not the best tactic.
     
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  13. Topher

    Topher Energy Curmudgeon

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    I did when I commuted in Boston. See, I don't care that a few or even 50 cars get in front of me, since it means that people trying to exit get to the correct lane sooner, so don't slam on the brakes at the last second, causing huge backups. Nor does it cause me to be late, 50 cars at 3 car lengths apiece is 3,000 feet, which I cover in less than a minute once traffic clears.



    Thank you kindly.
     
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  14. JohnSnowNW

    JohnSnowNW Active Member

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    TACC's, to an extent, behavior is based on the actions of the vehicle it's following, right?

    So, I blame the poor driving of the people ahead ;)
     
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  15. Topher

    Topher Energy Curmudgeon

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    Yes, this is actually one of my concerns. The algorithm for optimal driving in traffic, is NOT, follow the guy in front of you by a set distance, or even a distance determined by speed. I am hoping that Tesla can have cars start the transition to a more rational concept of driving in heavy traffic, certainly trying to convince humans to, has failed miserably.

    Thank you kindly.
     
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  16. BriansBucketList

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    Why do we care about people cutting in ? I drive 880 in Fremont all the time. Cutting in may or may not involve turn signals, and is closer to cutting you off. If you don't brake for a car coming in from the side, you end up in the body shop, and caught on dashcam, probably their fault for unsafe lane change. It's not about the delay, it's sort of hi way warfare, and the Tesla is well equipped to get both in, and out of trouble. Auto steer was stable today, but it's been acting funny over the last week. TACC is pretty predictable. I got from Fremont to Hayward hands off, Autosteer and TACC except for heavy merging, but I see it coming. It does not brake soon enough for cars about to hit your right front wheel well.
     
  17. Topher

    Topher Energy Curmudgeon

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    I don't want anyone who thinks of driving as 'warfare' on roads I share. Go drive in a demolition derby.

    Thank you kindly.
     
  18. kort677

    kort677 Active Member

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    #18 kort677, May 24, 2016
    Last edited: May 24, 2016
    I think you've taken the euphemism a little too literally. I know your views are not concurrent with those who do a lot of driving in congested urban traffic but many people that have to drive in those conditions usually learn that you need to be on your game. The TACC is what I call "chill" driving and doesn't cut it in that dog eat dog world of city driving.
    My saying is that bad things happen to those who are inattentive and don't keep up.
     
  19. SabrToothSqrl

    SabrToothSqrl Active Member

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    I left what I thought was too little room to be cut off... i was wrong. car hit me and I was Tesla-less for two weeks.

    If you show any weakness or gap, you're doomed.
     
  20. Max*

    Max* Autopilot != Autonomous

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    I noticed TACC is sensitive to the car in front of me (for obvious reasons).

    If the car in front of me is very jerky, TACC will be jerky. If the car in front of me is smooth, TACC will be smooth.

    So when I notice TACC to be jerky, I change lanes and/or pass the person in front.
     
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