Model S

Sudden braking on highway

My Tesla Model S has a sudden braking problem with no reason during driving on highway with the Autopilot. It has happened several times in the past a couple of months and the most times happened when I drive on the far left lane. It is very dangerous especially when some vehicle is following my car. Did anyone experience the same problem?

In addition, the far left lane is carpool lane on most freeway and I'm used to drive my Tesla on this lane during rush hours. However, the Autopilot always indicted me to change lane in order to leave the far left lane. Doesn't Tesla know that the electric cars are allowed to drive on the carpool lane?


  • Most likely caused by dark shadows or areas in the pavement ahead, or a mistake in the speed limit data base (often in areas of recent or current construction).

    Though I had a new instance of sudden braking today in an area that has been working - the new speed limit sign detection improperly applied a school zone speed limit (25 MPH) instead of the posted speed limit (40 MPH), even though I was driving through the area outside of the school zone hours.

    So... Is the AP software not only smart enough to detect the speed limit signs - can it also determine if the speed limit is actually active (looking for school zone times or detecting flashing lights indicating the school zone is active)???
  • Thank you for sharing your experience. However, I only use the Autopilot on highway where is no many speed limit sign changes. Moreover, it also happened on cloudy day that there is no shadow condition. So, I don't know what caused sudden braking in my case.
  • > @bp said:
    > So... Is the AP software not only smart enough to detect the speed limit signs - can it also determine if the speed limit is actually active (looking for school zone times or detecting flashing lights indicating the school zone is active)???

    So it appears that Tesla can change the speed limit but it only recognizes one type of speed limit sign for the country you are in. There have been examples of turning speedlimit signs being ignored, but at least Tesla slows down for turns anyway. When it comes to a school zone, if it's anything like the ones where I live, it's just a regular speedlimit sign but with lights above and a sign under that tells people that's only when it is flashing. A tesla is not going to register the other signs yet and they will just change the speed for any time of day.

    I'm sure eventually they will be able to recognize that it's only for some times of days but that could be a while. I can drive to a few different cities in my area and some of them have different school zone signs than others, so it will be a long time before it's perfect.

    Tesla is also close to it's next big update which should allow turning at intersections with FSD enabled. One thing I think could be a little problematic is signs that limit when you can make a turn. Near my work there is a no left turns between 7am-3pm, I'm assuming that the navigation software probably has most of these in the system but i've found a few where google maps have navigated me to turn when I wasn't allowed. I don't think Tesla would have a problem making the turn and would probably do it safely, I just don't want to get a ticket. I also hope that I can get Tesla to ignore the DO NOT ENTER signs outside my work, I really want to test Tesla's ability to drive me to work, but I don't think it'll drive past those signs
  • I replied to your duplicate post. No need to post the same thread twice.
  • I have a 12/2016 model S. I've had my vehicle brake suddenly on two separate occasions while traveling on Highway 99 in California. Both times it happened while approaching an overpass. First time a Mustang nearly rear-ended me. Then flipped me off as he passed me. Each time I took it to a service center. 1st time they said it occurred several weeks before I came in and there was no recorded history. 2nd time, they observed the episode in my cars history and said they adjusted the front camera! Still waiting for the next episode...this is a real safety hazard. I learned to be hyper vigilant and try to step on the accelerator once I'm sure there's no obstruction ahead.
  • I had it happen on I-80 between Reno and Winnemucca NV while passing a big rig, it suddenly slammed the brakes on and even though I was about 5 feet past the truck I slammed the accelerator to the floor to stop it's braking. the truck went past me. thank good that truck was not behind me it took over 1 second for the brakes to release.
    it has happened on plain country roads for no reason. about a dozen times now. I would say it is possible two of those were over passes.
  • I had it happen a few weeks ago on the freeway. It was not just once but three or four times on the way to my destination and again coming back a few hours later. I want to say it was shadows but I don’t really know. It’s startling for passengers and definitely dangerous. I stepped on the accelerator but that’s also a dangerous habit to get into.

    Haven’t had it happen since.
Sign In or Register to comment.