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6.2 TACC still following WAY too far behind

Discussion in 'Model S: Driving Dynamics' started by TesTes, Apr 1, 2015.

  1. TesTes

    TesTes New Member

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    Meh. 6.2 still following WAAAY too far behind. The drivers in Central Texas aren't even close to as aggressive as I've seen in many other states where I've lived... yet the TACC leaves a big enough gap that I'm perpetually getting others cutting in front of me and repeatedly pushing me back. And, yes... it's set to '1'.

    Thoughts?
     
  2. rickgt

    rickgt Enthusiast owner/member

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    i guess it's a function of how big a gap is considered too much... Maybe an adjustment is needed on your car. I usually use 2-3 as my setting, and not a problem on country roads. On busy freeway it's more aggressive and set to 1-2. Typically one to two car lengths.

    Are you wanting a distance less than a car length?
     
  3. NoMoGas

    NoMoGas Member

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    It's not going to put you too close for the car to stop if they stop short. I drive at 6-7 in LA traffic.
     
  4. wk057

    wk057 Senior Tinkerer

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    TACC distance is definitely fine. The car knows how far it needs to stop and won't violate that minimum if at all possible. Fine by me.
     
  5. krisg81

    krisg81 Member

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    This guy isn't too happy about the large gap either.

    628x471.jpg
     
  6. wk057

    wk057 Senior Tinkerer

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    He looks pretty happy about it to me. :tongue:
     
  7. billarnett

    billarnett Member

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    It seems to me that the TACC UI is wrong. Instead of the 1-7 following time (and it's really a time not a distance) it should instead simply maintain the same following time as it was when first engaged. Just like the way an ordinary CC works for speed. You pull up behind someone, engage TACC and it follows him at that separation (adjusted for speed) until you disengage. No need for any other control. (Maybe a max speed in case he decides to accelerate too much.)
     
  8. Burt Court

    Burt Court Member

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    NoMo...If I set mine at 6/7, I'd back all the way down to Mexico... 2 for me is even marginal at 70 mph in LA. I hate to be cut off so often
     
  9. wk057

    wk057 Senior Tinkerer

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    Horrible idea. You could be putting yourself in a situation where you and the car are unable to safely stop if the car you're following suddenly stopped. It would be pretty silly to allow a TACC following distance that is guaranteed to result in an accident if the car in front stopped suddenly, then have the car in front suddenly stop, and accident happen, and someone blaming Tesla/TACC.

    Never going to happen. The car is always going to maintain a safe distance even on 1. If the car can't stop in that gap in front, it's not going to follow that closely, period.

    Basically, what you folks who are complaining that it is too far back are actually saying is that you don't drive safely to begin with. ;)

    I personally leave TACC on 7. Safer, softer stops, etc. If someone jumps in front of me, so be it. Doesn't hurt my feelings. I'm a huge supporter of "KEEP RIGHT, PASS LEFT."
     
  10. Janos

    Janos New Member

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    First a constructive suggestion: If you're in heavy traffic, and detect an aggressive driver sizing up your safety zone, you CAN push the accelerator to close the gap manually. (Should that be pedally??) Then when the threat is over, you can let go and the TACC will take over to follow at a safe distance.

    That's the reality of human driving: as long as they're still allowed on the road some of them are going to be a hazard not just to themselves but to everyone around them.

    I'm pretty satisfied with the range of distances - my rough estimation is that 1 corresponds to a 1.5 second gap and 7 corresponds to a 3 second gap (anyone else confirmed this?). Given that the Old School best practice for a human driver is a 2 second gap, that's pretty safe and conservative for a computer. But I wouldn't want to go much closer than that: an alert human has a reaction time of around 1 second, so that 1.5 second gap is clearly assuming a faster reaction from the computer.
     
  11. loco

    loco Member

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    Funny, but I have been surprised at how small the gap is with Tesla. From my experience in Audi/BMW/Mercedes they leave a larger gap at closest setting. Can't prove it. Just an impression.

    When someone jumps in, I let the car slow down. I think it's related to age. I was constantly in the slipstream at 20 :)
     
  12. billarnett

    billarnett Member

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    Basically what you're saying is that you want the car to enforce what the manufacturer thinks is "safe" no matter what the driver thinks. But of course, there are dozens of ways to operate a car unsafely (eg 100 mph in a school zone) that the car allows. Why make a special case of following distance, especially since that's a particularly contentious issue? There are plenty of ways to use TACC unsafely, too, as the manual so often states.

    Let me make my own judgement about how to operate my car. (Legal issues are a whole other discussion.)

    - - - Updated - - -


    Maybe my old school is older than yours :) but the rule I was taught was "one car length per 10 mph" which come pretty close to one second with an average length car. That's what I grew up with and hence what feels "about right" to me. Obviously opinions vary. This is not really an objective issue.

    That said, it seems to me the rules are not the same for computers. A human reaction time may be 1/2 second or more but TACC can react in microseconds. A following distance of one INCH would be safely possible if it could engage full braking force (though it would be unnerving to the guy in front :)
     
  13. wk057

    wk057 Senior Tinkerer

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    Actually, for variables the car has control over at the time I much prefer that the car make the decision as to what is safe, in this case following distance and speed. But the car is not "enforcing" anything. You're still in control. (Based on the desire to tailgate, this is unfortunate.) If you want to tailgate while TACC is on just hit the accelerator. But if Tesla lets TACC tailgate on its own that would just be pretty dumb on their part. It's an assistance/safety feature. Why would it behave in an unsafe manner? That would be silly. Tesla is promoting autopilot/semi-autonomy/autonomy/etc as eventually being safer than a human.

    You also seem to misunderstand the laws of physics a bit. Under almost no conditions would a following distance of "one inch" be safe, even for the fastest computer. Not even at a of couple feet, most likely. The Model S weighs over two tons. If the car in front has a better stopping time then you're going to rear-end them. The car has no way to know the braking power of the car ahead, so the gap between vehicles has to be far enough so that if the car in front hits an invisible brick wall and comes to a dead stop almost instantly you still have enough room to stop safely. The car can calculate this safe distance based on speed and other factors pretty easily.
     
  14. Saghost

    Saghost Active Member

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    The car isn't enforcing anything under TACC - you always have the option of taking control and driving yourself info more dangerous conditions.

    What he was suggesting (and I agree with) is that Tesla design the automatic systems to operate in a manner they believe does not risk an accident. I find it hard to understand how anyone would want an automatic system to behave differently - why would you want an automatic system to knowingly court an accident? Who could justify that to insurance/shareholders/family members?

    (Note: I'm not passing judgement on the actual following distance set by TACC or ability of the car to stop under the current settings - just going off of your comment about the car enforcing whatever the company thinks is safe.)

    Collision avoidance braking is a different subject - that's where the car is actually enforcing a following distance it thinks is safe. We'll have to see how Tesla set that up on the new firmware.
    Walter
     
  15. jkirkebo

    jkirkebo Model S P85+ VIN 14420 EU

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    Funny, here in Norway the complaints are that the car is following too close even when set at 7...

    Setting 7 have been timed on the highway to 2.6 seconds here which is less than the 3 second recommended minimum.
     
  16. billarnett

    billarnett Member

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    "safe" and "tailgate" are not objective concepts, they're in the mind of the driver(s). There is wide variation. I'm actually fine with what TACC does; sometimes I use setting 1, sometimes 7; that seems to be a wide enough range for me. Others disagree. All I wanted to suggest is that there's a simple way to accommodate everyone's preferences by changing the way the driver specifies the following distance. I would be OK if it worked as I suggested above but TACC refused to set the gap to much less than the current setting 1. On wide open rural freeways I think I might like a setting much more than the current 7.

    OK, I exaggerated. But it's not reasonable to plan for a brick wall in the middle of the freeway. All you really have to do is leave enough room for your reaction time (or your computer's) plus the difference in stopping distance between you and the guy in front. That difference is likely to be negative with a Model S :) and in the worst case not more than a couple hundred milliseconds. 10 or 20 feet at 65 mph ought to work for a computer with microsecond reaction time.

    Anyway, leaving as much room as you suggest is just not practical in heavy traffic. Cars will quickly pull in in front of you. Yes, you can then slow down even more. Then another car will pull in front. Ad infinitum. The net result is that you have cars manouvering in front of you all the time, surely a more dangerous situation overall than a somewhat closer following distance. Not to mention the fact that you'll be annoying 1/2 the other drivers on the road.

    (If they wanted to, Tesla could recognize the make/model of the car in front and look up its best stopping distance in a little database and use that to compute the safe gap. Probably not worth the effort. In a future world, the two cars could communicate this info to each other. Reducing safe following distances could greatly increase the carrying capacity of the freeways.)

    - - - Updated - - -

    TACC is enforcing its judgement to the extent that the feature is not available to those whose judgement differs. And I don't think that's actually the judgement of Tesla's engineers. It's more likely to be the judgement of lawyers more concerned with bad publicity than physics.

    - - - Updated - - -

    Methinks your 3 second recommendation must have something to do with your latitude :)
     
  17. wk057

    wk057 Senior Tinkerer

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    #17 wk057, Apr 2, 2015
    Last edited: Apr 2, 2015
    Then you need to account for differences in pavement, weather, road hazards (oil, etc), among other things. Then you have the worst case: say a car from the other direction cut over and smashed into the car in front of you head on at relatively the same speed. Not a brick wall, but same result: instant dead stop. At 20 ft following distance, 65 MPH, let's say the car applies the brakes to full power within 100ms (would be impressive)... you'd be about 90 ft through the car in front by the time you stopped. lol. (Guess I could calculate about how far you'd push the two car pile up in front on impact with all of that extra kinetic energy... maybe later)

    Plan for the worst, hope for the best. Since the computer has no way to "hope" and only a way to plan, let's stick with safety first.

    Sounds like you'd be that guy who rides the left lane at the speed you decide rather than the flow of traffic or to pass. That is the only situation where I get in front of someone and become annoyed that they were in my way. Keep right, pass left. If the people cutting in front of you are coming from the right, you're in the wrong lane. If they're coming from the left, I don't see what the problem is. Either way, can still maintain a safe following distance regardless.

    See first part of the post for an example of why this is still a bad idea until there is car-to-car communication with all vehicles on a road.

    Edit: I also feel the need to point out that the equipment in the Model S does not have "microsecond" reaction time. All of the data I have gathered suggests that the car updates information about the other vehicles around it from the camera and radar every 28ms-33ms. Plus braking isn't instantaneous either. The car still has to press the brake pedal, which takes a macroscopic amount from the viewpoint of time to the computer.
     
  18. billarnett

    billarnett Member

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    In heavy traffic I usually sit in the left lane following the guy in front. If there's so little traffic that the left lane of open for passing most of the time then I usually drive in the left lane or the one next to it at the speed limit +10 but I move over when someone comes up behind.

    I don't want to get into a big discussion about what's safe/courteous/etc. I think we can both agree that there is a wide variation in drivers' judgements in this respect. (And there are regional differences in the aggregate expectations; what's generally rude in NC may be generally accepted in CA.)

    Good point about the Model S update rate. But of course, that could be shortened if there was a good reason to do so.
     
  19. mikeash

    mikeash Active Member

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    The 1 setting is really close in my opinion. If people are still squeezing in front of you at that setting, I say let them. There's no need to stress about people trying to get ahead of you.
     
  20. CHG-ON

    CHG-ON Still in love after all these miles

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    #20 CHG-ON, Apr 2, 2015
    Last edited: Apr 2, 2015
    I'm a huge supporter of "KEEP RIGHT, PASS LEFT."

    AMEN WK057!!!

    Perhaps the best solution to how close or far we should be could be solved in firmware 8.0, where Tesla installs an ion cannon in the grill and simply vaporizes the car in front during an impending collision. Though I would probably use it daily...
     

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