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Why does TACC not respond to the distance control setting when AP does?

Discussion in 'Model S' started by thegruf, Dec 18, 2016.

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  1. thegruf

    thegruf Active Member

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    Been using TACC more recently due to muck on some roads at this time of the year making AP less reliable.

    Curiously I found that changing the setting on the cruise stalk from 1-7 makes no difference to tthe following distance with TACC. The cruise is still working actively as it will vary speed according to the vehicle in front but only at a fixed (and too close for my preference) distance.

    I assume everyone else has the same behaviour.
    I don't understand why this is.
    Can somebody explain the logic to me please.
     
  2. mblakele

    mblakele radial cross member

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    I haven't noticed that behavior. Yesterday I drove over an hour with TACC alone, and the following distance seemed to be about right: I have mine set to 3, and it maintains about three seconds.

    The latest manual I have says that "If a vehicle is detected, Traffic-Aware Cruise Control maintains your chosen following distance, up to the set speed" (2016-10-20 edition, p67): https://www.tesla.com/sites/default/files/model_s_owners_manual_north_america_en_us.pdf
     
  3. BerTX

    BerTX Active Member

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    I guess I'm too old to answer this question. My TACC is always set on 7 and would be higher if there was another click or two. I rarely even get the chance to use Auto-steer, as I mostly drive on hilly, two-lane roads. I have re-named it Auto-suicide for the way it veers into oncoming traffic at the top of the hill. Who came up with the "I can't see the lane markers anymore, so I'll steer left" algorithm? I shake my head when people talk about using it with oncoming traffic. Somebody's gonna die.
     
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  4. dhcp

    dhcp Member

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    If you drove the Bay Area commutes with anything than three you would have a constant flood of people cutting in front of you until your car slowed down to a stop. I usually run 3 but sometimes have to go to 2 else the car jerks back on the brakes when another car cuts in front of you.

    Auto-suicide, love that. :)
     
  5. jdw

    jdw Supporting Member

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    In Montreal, I drive on 1 and people still cut in front of me constantly … especially annoying when there is plenty of room behind me. Every city has a driving personality.
     
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  6. dhcp

    dhcp Member

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    Yikes!!
     
  7. jdw

    jdw Supporting Member

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    Yeah ... I'm planning a Dashcam mashup of some of the best moves.
     
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  8. Saghost

    Saghost Active Member

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    I haven't had occasion to change the distance settings while in TACC but not AP - but I have spent a fair amount of time that way, and the distance has always matched the AP distance for the setting.

    The distance is really a TACC feature anyway - and AP is really TACC plus AutoSteer, not some completely separate driving logic.

    Are you certain of your observations?

    In my experience, it takes the car several seconds to set a new following distance after the lever is moved - especially if the car in front is going slightly faster than you are.

    (And yes, drivers on I-95 will angrily move from behind you, pass you on the right and cut in on 2 or 3, and occasionally on 1, during morning and afternoon commutes. People be crazy.)
     
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  9. Moonwick

    Moonwick Member

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    I haven't noticed this behavior either. I do notice that OP is in the UK; is it possible that the behavior is different there due to local laws?
     
  10. RDoc

    RDoc S85D

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    Yes, I'd like fractional settings for the same reason.
     
  11. WannabeOwner

    WannabeOwner Active Member

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    I've fiddled with my follow-interval from time to time and concluded that it doesn't seem to make a lot of difference; well ... I expected it to make far more difference. I'll try a more scientific test, timing follow-distance with a stopwatch, next time I'm on a motorway.
     
  12. ccharleb

    ccharleb Member

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    Or you could do a very simple test. Activate TACC at setting 7. Catch up a car and be sure that desire speed is higher than what the car ahead is doing. After a minute or two following the car ahead slower than desire speed, change following distance setting from 7 to 1. Your car should accelerate to get closer to car ahead.
     
  13. ecarfan

    ecarfan Well-Known Member

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    I have spent a few hours in total driving with TACC earlier this year (not with V8 firmware) and found it to definitely change following distance with setting changes.

    Note: the numerical settings are not in units of "seconds" of time between you and the car you are following. This has been extensively discussed in multiple threads in the past on TMC. It is simply a numerical scale. Choose the setting that provides a distance you are comfortable with. I always used 7 on Southern California freeways, I was not comfortable with any lower number. Obviously many people are okay with lower numbers. Not me.
     
  14. croman

    croman Active Member

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    I believe the settings are a fixed distance called "car lengths" which is 9 feet. Safe following distance is 2 seconds. 2 seconds of following distance varies based on your speed.
     
  15. MP3Mike

    MP3Mike Active Member

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    @croman Not according to the Tesla manual: "Adjust your following distance
    To adjust the distance you want to maintain
    between Model S and a vehicle traveling
    ahead of you, rotate the cruise control lever to
    choose a setting from 1 (the closest following
    distance) to 7 (the longest following distance).
    Each setting corresponds to a time-based
    distance that represents how long it takes for
    Model S, from its current location, to reach the
    location of the rear bumper of the vehicle
    ahead.
    "

    So it is a time-based setting, they just don't say what time a 1 vs. a 7 represents.
     
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  16. croman

    croman Active Member

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    Interesting. That is NOT what my OA told me nor was it what EM mentioned when TACC was first released but I trust the OM to clearly state it. Thanks!
     

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