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Sudden Slow Down with Cruise Control
Today I made a long highway drive. The speed limit is 75mph, the car correctly noted the speed limit, and I set the adaptive cruise control at 75. I was not using autosteer.
Suddenly, for no apparent reason the car abruptly slowed. This really caught me by surprise. I glanced at the screen, it showed speed limit 35mph although there was no actual speed limit change on the road. What was much worse was that the setting on the ACC changed itself to 35mph! The deceleration was so fast that the car slowed to about 55 before I was able to act by accelerating and cranking the ACC setting back up to 75. Lucky there weren’t many cars on the road or this might have caused a bad accident.
I can’t fault the system for having an error in its speed limit files. But any cruise control should stay where I set it unless there is a slow car ahead or I make the change.
Is there some way I can stop this behavior so that the speed I set always remains until I change it? What it did today was scary and just plain dangerous. I’ll have a hard time trusting this basic system in the future.
Suddenly, for no apparent reason the car abruptly slowed. This really caught me by surprise. I glanced at the screen, it showed speed limit 35mph although there was no actual speed limit change on the road. What was much worse was that the setting on the ACC changed itself to 35mph! The deceleration was so fast that the car slowed to about 55 before I was able to act by accelerating and cranking the ACC setting back up to 75. Lucky there weren’t many cars on the road or this might have caused a bad accident.
I can’t fault the system for having an error in its speed limit files. But any cruise control should stay where I set it unless there is a slow car ahead or I make the change.
Is there some way I can stop this behavior so that the speed I set always remains until I change it? What it did today was scary and just plain dangerous. I’ll have a hard time trusting this basic system in the future.
3
Comments
Thank you for allowing me to vent. I have not run out of four letter words as some other writers suggest, but have spared you all that. :)
What software version are you at? Did you save the dash cam video? Where exactly were you? Highway and mile marker. Did you do a bug report?
RUSirius is the banned trill, FISHEV. Flag and nice on so the @Forum_Admin can block access, for the fifth time.
When you can see the speed limit drop on the screen, you know why the car did it, and the car did it for a specific and correct reason. It just has bad data.
> Today I made a long highway drive. The speed limit is 75mph, the car correctly noted the speed limit, and I set the adaptive cruise control at 75. I was not using autosteer.
>
> Suddenly, for no apparent reason the car abruptly slowed. This really caught me by surprise. I glanced at the screen, it showed speed limit 35mph although there was no actual speed limit change on the road. What was much worse was that the setting on the ACC changed itself to 35mph! The deceleration was so fast that the car slowed to about 55 before I was able to act by accelerating and cranking the ACC setting back up to 75. Lucky there weren’t many cars on the road or this might have caused a bad accident.
>
> I can’t fault the system for having an error in its speed limit files. But any cruise control should stay where I set it unless there is a slow car ahead or I make the change.
>
> Is there some way I can stop this behavior so that the speed I set always remains until I change it? What it did today was scary and just plain dangerous. I’ll have a hard time trusting this basic system in the future.
Got the same exact issue (but from 65mph). The setting changed itself to 35 with a sudden brake. I understand geomapping and other thing, but why Tesla is the only car with this feature, that has this issue. My previous car (Stinger GT2) had something similar called smart cruise control. I know it is different as it doesn't rely on GPS but at this point I would prefer a "simpler" cruise control. I understand that there are no accidents reported due to this issue, but that is not the point. It is scary, and actually dangerous. I personally stopped using it, as here in the LA area the traffic is (in my opinion) too intense to risk it again. All said, I love the car, but I think something should be done in regards, as way too many people reported/experienced this.
RSX50, I totally hear you.
FrankyMN,
What software version are you at? Did you save the dash cam video? Where exactly were you? Highway and mile marker. Did you do a bug report?
> Lets try this a 3rd Time.......
>
> FrankyMN,
>
> What software version are you at? Did you save the dash cam video? Where exactly were you? Highway and mile marker. Did you do a bug report?
I think I already replied to this in an another thread. I was in the last update 2020.35.something, US 101, don't remember the mile. I didn't reported the bug, as I was not aware that this is something that happens often. At the time I had no idea what happened. I was with a passenger, and we both got quite scared. That night I joined this forum to see what people knew about, and found out that is quite common. Haven't used AP (apart areas with no traffic) since that time to be honest, I am quite scared
> > @HAL2001 said:
> > Lets try this a 3rd Time.......
> >
> > FrankyMN,
> >
> > What software version are you at? Did you save the dash cam video? Where exactly were you? Highway and mile marker. Did you do a bug report?
>
> I think I already replied to this in an another thread. I was in the last update 2020.35.something, US 101, don't remember the mile. I didn't reported the bug, as I was not aware that this is something that happens often. At the time I had no idea what happened. I was with a passenger, and we both got quite scared. That night I joined this forum to see what people knew about, and found out that is quite common. Haven't used AP (apart areas with no traffic) since that time to be honest, I am quite scared
Sorry 2020.48.35, the Christmas one with the boombox
> Our local state highway has some mapping issues with regards to incorrect speed limits. One 55 mph zone is mapped at 45 and another 30 MPH area is mapped to 45 as well. Knowledge is power. Google is not always right. The car is just following bad code. Respond accordingly.
I understand, but this sounds like pushing the problem to someone else. The car is made by Tesla, and I am expecting the problem to be fixed by Tesla, not Google. If the issue originates from Google then Tesla should find a way to fix this.
> You were so scared you forgot where it happened? Just US101? In CA, OR, TN? Near? It actually doesnt happen often, it does happen but its rare. Most of the phantom braking posts on this forum have been proven to be hit and run trolls.
You can think whatever you want about my experience. But it happened, it was real, no troll. It was scary, luckily didn't crash. If you have to bully people because you are braver then them cause you don't get scared, and this things are totally acceptable to you because you are always in control, fine by me, but leave us alone to report issues and be constructive. I am not attacking Telsa, I don't regret to have bought one, but this is a real dangerous issue, and must be fixed. Period.
Relax. It's a known problem, it happens to all of us, and it has several different causes. I've had it happen a bunch of times in my 3 nearly 3 years of ownership, but I couldn't tell you precisely WHERE any one of them happened.
There's no sense in attacking people who come in and report this issue, even if it's the hundredth time we've seen a post about it, because to them it exists, it's new, and it scares the crap out of them the first time it happens. Yes, people should search for existing topics (but that's a very advanced skill on this forum), but my 30 years on the Internet have taught me that people won't; and bitching about people who don't doesn't solve anything either.
And I'll throw my hat in with those who really hope that the next major rev of AP handles phantom braking, and phantom speed limit changes, a whole lot better than the current code does.
> What software version are you at? Did you save the dash cam video? Where exactly were you? Highway and mile marker. Did you do a bug report?
Sorry about my delayed reply. We’ve been a little distracted in Texas lately.
Here are my answers and thoughts about this:
Using the most recent software. It just downloaded and installed yesterday. I was on Texas 71, about midway between Austin and I 10 when this occurred. I was shocked by what happened and no, I did not notice the mile marker. No dash cam saved and no bug report.
As I stated, I can understand if the software has a mapping error and an incorrect speed limit. However, I do not expect the cruise control “speed limit” to override my setting on the cruise control. If the software wants to warn me that I might be speeding, that’s OK. The software has no right to suddenly slow my car on its own to match the speed limit. Tesla is not the police!
IMHO, this is analogous to what the software did in the Boeing 737 Max to cause those two crashes – the “brilliant” software overrode the pilot’s judgment - with disastrous results!
I was responding to the OP, not you.
> You can think whatever you want about my experience. But it happened, it was real, no troll. It was scary, luckily didn't crash. If you have to bully people because you are braver then them cause you don't get scared, and this things are totally acceptable to you because you are always in control, fine by me, but leave us alone to report issues and be constructive. I am not attacking Telsa, I don't regret to have bought one, but this is a real dangerous issue, and must be fixed. Period.
Re-read my post I did not call you a Troll. And where did I bully you? Where did I say it was acceptable? Why so defensive? You stated you were scared and your lucky you didn't crash but the only info you provided is US101 which practically runs runs across the entire US. To identify the cause a location is needed. I am simply confused that you were so scared and almost crashed but you cant remember where it happened. It was just 3 weeks ago.
When you say leave "us" alone to report issues, who is "us"? Your on a forum where users help users so who are you reporting your issues too by posting here? Are you not here for help from other users? If so you need to give some helpful information.
Phantom braking is a target topic for the Trolls here. They constantly make up fake posts. Never did I say your problem was fake. I simply countered your statement that it "happens often" with my statement that Trolls frequently fake it. That is not calling you a Troll.
So if you want help, Pretend this post is Tesla and your reporting the problem to them so they can fix it. Your version is 2020.35.x and you where going 65 MPH, and it reset to 35 MPH. It happened on January 23rd 2021. Where did it happen?
> 737 Max analogy is not close to being apt. That program fought pilots to the death. Tapping the accelerator is all this takes to override. Not everyone is cut out to be an early adopter.
You are correct. Overstatement on my part.
Still, there should be a setting that allows me to manually set the cruise control and not be overridden by the car’s assessment of speed limit.
I will state again: Tesla is not the police. They are not my mommy. They should not reset the cruise control to the speed limit.
> There's no sense in attacking people who come in and report this issue,
Seriously, where did I attack him? Please point out my attack and I will apologize immediately.