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Defensive Driving in the Model S

Discussion in 'Model S: Driving Dynamics' started by PureAmps, Jan 9, 2013.

  1. PureAmps

    PureAmps Model S P85 (#2817)

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    After driving the Model S for a couple of weeks now, I'm realizing that I have to modify some of my defensive driving habits that I've learned over the years.

    The most obvious is "covering the break" (taking your foot off the accelerator pedal and hovering over the brake pedal) which I do so often and instinctively, I don't really even think about it anymore. With the Model S, there is less of a need, because the accelerator pedal has enough "braking" capability that it works in most (but not all) circumstances. However, I have had circumstances in the past where I want to be prepared to brake hard, but still keep "coasting" in the meantime. This seems more difficult in the Model S, and would require me to hover over the brake pedal with my left foot.

    The other behavior is using the brake pedal to signal intent to the driver behind me. Maybe they are following too close so I'll give a light tap on the brake, to give them a heads up before I really start braking. Or sometimes a few taps to "flash" the brake lights. This is a little harder to manage, since it is not obvious when your brake lights are on during regenerative braking.

    Anybody else having to adapt their defensive driving behaviors?
     
  2. ViperDoc

    ViperDoc Roadster 1305

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    Defense ideas

    I do a lot of driving in cruise control on the highway (at least in my Roadster, my wife has the Model S most of the time) and still have my foot ready to hit the brake if needed. In terms of tapping the break, one option for would be to flash the emergency blinkers a couple of times. It would require developing a different "muscle memory" but would produce the same effect for the trailing driver.

    David
     
  3. MikeK

    MikeK R#129, TSLA shareholder

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    I've noticed the same thing. I'm used to covering the brake, and this is essentially impossible if you want to have regen turned on.

    I just drove an hour in lousy traffic, and I couldn't help worrying whether the drivers behind me were getting brake lights at the right times. A little deceleration under regen doesn't turn the brake lights on, but I guess it doesn't in a stick shift either.
     
  4. Doug_G

    Doug_G Lead Moderator

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    Another important defensive driving technique is to realize: people don't know your acceleration capabilities, and they won't hear you gunning it, either.

    This can be very important when accelerating out of an intersection. You can achieve very fast acceleration rates without a lot of noise and commotion. You can easily catch up to someone who thinks he is all alone, just in time for them to change lanes without signalling (well they ARE all alone, right???). This has happened to me in my Roadster on quite a few occasions. I've seen some very shocked "where the heck did he come from?" expressions when they realized they cut me off. You don't need to have your foot to the floor for this to happen.

    People also sometimes turn right on a red, just as you're accelerating at the fresh green light, and they don't realize that you're already on top of them. They glanced a couple of seconds ago and you weren't moving at the time.

    Fortunately I had already been warned by others on the forum about these possibilities, and have always been prepared. That has kept me safe. Keep that in mind!!!

    (On the other hand, I've had a few occasions to use full throttle to prevent an accident - it does give you more possible ways to escape.)
     
  5. vfx

    vfx Well-Known Member

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    You can do this with a just a quick lift off the accelerator. Your car's accelerometer will put your brake lights on. In the Roadster you can see it reflected in the wing so you can get a feel for learning it. Some simple optical device (like apiece of paper) might work for the Models S. We have had discussions about have a light on the dash for when the regen brake light comes on. Maybe we revisit that for the S.
     
  6. PureAmps

    PureAmps Model S P85 (#2817)

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    Funny you mention this, because I've already encountered it. I was getting on a freeway following a "slow" moving car that can't do 0-60 in less than 5 secs. :) He was slowly (by my new standards) getting up to freeway speed in the far right lane. I decided to pass him on the left, and sure enough he tried to move left over into my lane and had no idea I was already there (because I wasn't a second earlier). Luckily no harm done. I think we were both a little surprised. :eek:

    I'm a little more cautious now when I overtake someone in those circumstances. Amazing how a little thing like "engine noise" makes a big difference in our driving behavior...
     
  7. jomo25

    jomo25 P4398

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    I know there's a screen that has a picture of the car and the appropriate light flashes when you turn on your turn signal. Is there a similar screen showing the back of the car that will show when the brake lights go on? If so, it can be used to get a feel for how much deceleration triggers the light.
     
  8. MikeK

    MikeK R#129, TSLA shareholder

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    Yes. If you bring up the info screen that shows your software version (by touching the Tesla logo at the top of the 17" display), then you see a depiction of the car, and you can see the high-mounted brake lights and one of the tail lights in that image. They do light up with the brake lights are on. If the headlights are on, the tail light will already be glowing, so it glows brighter if the brake comes on, but that can be hard to distinguish. The high-mount is pretty clear.

    I've been planning to have a passenger ride along and call out changes in those lights while I concentrate on driving.
     
  9. Doug_G

    Doug_G Lead Moderator

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    At night, if you're not under bright overhead lights, you can more easily see the brake lights turn on by watching the rear view camera - the brake lights illuminate the ground nicely.

    The Model S regenerative braking lights behave rather differently from the Roadster. The Roadster's brake lights come on at any speed (above creep mode), when you're about half-way off the pedal. For the Model S, I find they don't ever come on at highway speeds, above about 70 kph. Below that they come on when you are close to full regen.

    For all I know they have the same algorithm; perhaps the difference is due to the stronger regen deceleration in the Roadster.
     
  10. olanmills

    olanmills Member

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    They come on based on an accelerometer, so it depends on the rate of change in speed, not the speed itself.

    I found that it works quite nicely. If you're coasting on flat ground in an ICE, and you start slowing down, but you don't hit the brakes, no brake lights come on, right? Well the Model S sort of does the same thing. If you're regen braking, but the rate of change in your speed is similar to coasting in an ICE car, the brake lights don't come on.

    The main difference is that going downhill, ICE drivers need to press the brakes to hold speed or slow down, which is not always true in the Model S, depending on the grade of the slope and your speed. And then in the opposite scenario, going uphill, if an ICE car needs to stop (but not suddenly), they don't need to press the brakes until the very end, and so if the hill is steep enough, they can slow down quite quickly without the brake lights coming on, whereas with the Model S, if you let off the accelerator going uphill, if the car detects that the rate of speed change is great enough, the brake lights will come on.
     

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