TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC

Autopilot limitation/warning. FYI/PSA

Discussion in 'Model X: Driving Dynamics' started by Leodoc, Jun 27, 2018.

  1. Leodoc

    Leodoc Member

    Joined:
    Jan 25, 2016
    Messages:
    88
    Location:
    South Florida
    Hi everyone,

    I wanted to post this as an educational piece, as it were. We have owned a MX for almost 2 years now. We have AP1 and have been MORE THAN HAPPY with it. I personally have logged an excess of 15-20k miles in AP. Let's just say, I'm pretty experienced with AP, its' benefits, and its' limitations. I've read all the accidents that have happened and feel that I am pretty aware of how the system works.

    Before I move one, let me say the following. What happened to me a few days ago was NOT the MX's total fault. I have plenty of blame to take for this. I wanted to put this out as a PSA for those that may run into what I did.

    So I was on the highway. Stop and go traffic. Never climbing to more than 15-20mph for about 10 minutes. This almost feels like the best situation for autopilot. Tessa handles the lanes and the stopping/going without much issue. She's even gotten better over the years with abrupt acceleration/deceleration. So the car in front of me stopped abruptly....and Tessa recognized it and sounded the alarms. This isn't the first time that the alarm for front end collision came up.

    **quick aside**
    So with forward collision warning systems, it's quite the paradox. In some cars, you can play with its' senstivity. If you turn it too high up, you'll get a lot of beeping and alarming...even in situations where you intended on braking with more than enough time. That may have the unfortunate effect of causing a little bit of laziness. Truth be told, the MX is my wife's daily driver. I drive a C63 AMG-s. I have taken Merc's track day course in Road Atlanta. We had that alarm system go off multiple times while taking the Mercs around the track. I almost lazily felt like the system was a warning, but that it didn't necessarily mean that a collision was imminent. In the case of the tesla, i felt like the AP would understand the warning and brake HARD.

    So onwarrd.....

    I reacted slowly...by probably a tenth of a second. As soon as I realized the MX's braking wouldn't stop me in time, I performed an emergency brake. I couldn't go right or left so I just floored the brake. Well...I stopped about 1-2" too late and I hit the pickup in front of me. His car took zero damage but I have a damaged bumper/hood to show for my stupidity. To be fair, I was looking down at the time. Had I been FULLY paying attention to what was in front of me (driving without AP activated), I likely would've reacted quicker and not hit the car in front of me. I was over-reliant on AP and its' ability to brake correctly.

    Which leads me to my teaching points:

    1. The Tesla will NOT ALWAYS stop in time...even under the best circumstances. This wasn't a situation where someone pulled out in front of me and there was a stationary object. This was literally just straight forward stop and go traffic.

    2. In respects to #1, as Tesla always says, PAY ATTENTION to what is in front of you. The obvious limitation to radar sensed cruise control is that until the car in front of you begins to decelerate, your car won't decelerate. Your eyes may see something before the radar does. In my case, that .2 seconds that my eyes would've seen something may have saved me a visit to a body shop and paying my deductible for body work.

    3. This sounds simple, but If/when you hear the forward collision warning, do not wait to see if the car will brake...immediately take control of the braking. The .1 second that I hesitated, lost me 1-2" of stopping and thus, THUMP.

    4. I've considered widening the following distance in the future for stop and go traffic. My logic being that the farther away I follow the car in front of me, the more time to brake. Perhaps it is something to consider? When in stop and go traffic, widen your following distance?

    That is all. I hope that my experience helps someone else out. I just ordered my Model 3 (Performance) this morning and will be cautious when it replaces my merc as my daily driver.
     
    • Informative x 1
  2. boaterva

    boaterva Supporting Member

    Joined:
    Apr 2, 2016
    Messages:
    5,142
    Location:
    Northern Virginia, USA
    Thanks for your story and hope you get the damage repaired quickly! I wonder if your AP1 experience is 100% relatable to AP2.x? What was your following distance set to? I use ‘2’ all the time and I think that leaves a lot of distance. But I’ve never had the car in front of me lock them up in stop and go!

    It appears to be about 2 seconds which may or may not be the ‘plan’ of the setting. I’ll have to see and ‘measure’ at stop and go speeds how much room we have.
     
  3. Leodoc

    Leodoc Member

    Joined:
    Jan 25, 2016
    Messages:
    88
    Location:
    South Florida
    I HAD it set to the closest setting. In south florida, you leave too much room and EVERYONE gets in front of you. :D

    I've since changed it.

    In regards to AP1 v AP2, I believe the ACC works the same in both cars...simply radar sensed...but don't quote me.
     
    • Funny x 1
  4. RedOctober

    RedOctober Member

    Joined:
    Oct 31, 2017
    Messages:
    212
    Location:
    Oro-Medonte
    It’s refreshing to read a post where the operator made a mistake and owned up to it. Many complain about the car be it a Tesla or a legacy vehicle. I found if I set my distance too far people just pull in between me and the car I’m following as well. To my surprise it handles that pretty well without slamming on the brakes.
     
  5. Brian's ReX

    Brian's ReX Member

    Joined:
    Jun 26, 2018
    Messages:
    54
    Location:
    Seattle
    Ditto! So, thank you Leodoc! I feel it's imperative that we, as Tesla owners (and IMO, in ALL aspects of life) own up to our mistakes. Doing so only strengthens Tesla's ability to determine what real-world situations we are all dealing with.

    For this reason, I let Tesla monitor my driving in the unlikely (*knocking on wood) event that I do something totally stupid and am not around after-the-fact to tell my story. I want all to know it was MY stupidity... not a fault of Tesla's. Unless... it IS. :p

    Regarding the OP's situation: My AP2 has always (*again, knocking on wood) done a perfect job of stopping, even when the situation requires ReX to stomp on the brakes.

    I am fluid in setting my following distance. Generally, in 40+ traffic, I'll set it to 4-5ish. In stop and go, I'll go down to 2 - for the same reason (get sick of people getting in front of me, thus making me feel like I'm going 'backwards'). I don't like 1.

    What I've noticed when others get in front of me whilst using AP (which, you will find in my posts, I use pretty much EVERY time I'm allowed - but I ALWAYS am ready to take over), or TACC, is this: When the other vehicle is merging in front of me and they are going as fast or faster than I am, ReX reacts beautifully - gradually letting itself get to the distance setting. However, if said vehicle is going any fraction of an MPH slower than I... ReX hammers the breaks/regen.

    This second scenario is VERY alarming in that many other drivers (read: idiots) like to follow proverbial inches from my rear bumper! I know others in this forum have mentioned this very thing... but Lordy! I don't know if Tesla has some algorithm that takes the following vehicle into consideration whilst determining how hard to slam on the brakes... but if so, it doesn't seem to do a very good job.

    More than once have I had a following vehicle think I have "brake-checked" them, and then race around me (as much 'racing' as one can do in crappy traffic) and brake-check me right back! Not sure what can be done about this, but TACC and AP should be making traffic safer... not creating problems. I am, as noted, fully aware - and pushing the accelerator to minimize the issue with the following vehicle... but the 'damage' has been done, and the following experienced driver (read, again: idiot) gets their undies in a knot.

    Other than that, AP works beautifully for me. My stress level in S&G traffic is dramatically lower since getting my X!
     
  6. ecarfan

    ecarfan Well-Known Member

    Joined:
    Sep 21, 2013
    Messages:
    15,152
    Location:
    San Mateo, CA
    True. And Tesla makes no claim that TACC will always brake in time when a vehicle it is following brakes suddenly.
    I think that is unlikely. The radar and firmware can probably detect the vehicle ahead decelerating before your eyes can, and can certainly react to such deceleration and apply the brakes more quickly than you can. The time you take to detect the deceleration, have multiple brain centers process than and then send the signal to your leg muscles to move your foot and apply the brake is far longer than what TACC takes. I’m a neurophysiologist and I know a little bit about that.

    That said, as already noted Tesla makes no claims that all forward collisions will be avoided when using TACC.
    You don’t say what interval setting you were using. I always use 7. Always. That gives my slow nervous system more time to react if I decide that TACC is not going to be able to avoid a collision. I recommend you do the same.
     
  7. Brian's ReX

    Brian's ReX Member

    Joined:
    Jun 26, 2018
    Messages:
    54
    Location:
    Seattle
    While I agree with this statement, and by no means do I rely on the vehicle to do everything (or anything, for that matter) for me in an emergency situation... Why would it not stop the car when necessity compels? At least slam on the brakes to mitigate damage?

    Granted, I am neither a neurophysiologist nor a radar expert. But I thought the constant radar/sonar/whatever was there watching ever so diligently, many times per second? Again, I don't rely on my vehicle to stop me, but I thought that was part of the 'safety features' built in to so many new vehicles... Tesla notwithstanding.

    So these stories of the vehicle running into leading cars is somewhat alarming. From a light tap on the bumper, to a 60-to-zero smack into a non-moving fire truck. I can't help but wonder: Do my car's sensors, like my own, occasionally 'zone out'? Lull themselves into a sense of complacency?

    This is why I am constantly monitoring my AP, which I use almost excessively.
     
    • Like x 2
  8. ecarfan

    ecarfan Well-Known Member

    Joined:
    Sep 21, 2013
    Messages:
    15,152
    Location:
    San Mateo, CA
    Tesla’s AEB function (Automatic Emergency Braking) is designed to engage and brake to reduce the speed of impact when the software determines that a collision is highly likely. It is not perfect, and Tesla specifically states that it is not guaranteed to avoid all collisions.

    I’m not an autonomous driving expert. But based on my research, it seems clear that designing a system to avoid all collisions is an extremely difficult problem, one which humans routinely fail at, obviously. A major challenge for AEB is...all the human drivers around the car. They sometime do things that are unpredictable and frankly, crazy. They overreact to perceived threats and don’t react at all to real threats because they aren’t watching the road.

    Tesla is constantly working to improve their AEB function, as are many other car manufacturers. Keep in mind that Tesla has only included AEB in their cars for a few years. So they’ve come a long way in a relatively short period of time.
     
  9. Brian's ReX

    Brian's ReX Member

    Joined:
    Jun 26, 2018
    Messages:
    54
    Location:
    Seattle
    @ecarfan: All very good points, and well stated. Teaching a logical 'brain' to determine what other 'brains', and many times 'illogical' brains at that, are thinking would pose quite the challenge.

    I say this quite often: All the more reason I don't fully relax whist on AP!
     
  10. mattack4000

    mattack4000 Member

    Joined:
    Oct 1, 2017
    Messages:
    870
    Location:
    CA
    Warning: Forward Collision Warning is for guidance purposes only and is not a substitute for attentive driving and sound judgment. Keep your eyes on the road when driving and never depend on Forward Collision Warning to warn you of a potential collision. Several factors can reduce or impair performance, causing either unnecessary, invalid, inaccurate, or missed warnings. Depending on Forward Collision Warning to warn you of a potential collision can result in serious injury or death.
    Warning: Automatic Emergency Braking is not designed to prevent a collision. At best, it can minimize the impact of a frontal collision by attempting to reduce your driving speed. Depending on Automatic Emergency Braking to avoid a collision can result in serious injury or death.
     
  11. Blastphemy

    Blastphemy Member

    Joined:
    Jan 11, 2012
    Messages:
    624
    Location:
    Los Angeles, CA
    Emergency braking on Teslas is worthless. I don't ever trust my Model X to stop unless AutoSteer or TACC is on. Whereas in my 2010 Infiniti FX50 (eight years ago!), Forward Collision Intervention worked flawlessly, always bringing the car to a complete stop in emergencies where I didn't react quickly enough. The technology exists; for some reason it ain't in our Teslas.
     
    • Like x 1

Share This Page

  • About Us

    Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.
  • Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


    SUPPORT TMC