Sudden Slowing and Cruise Control Speed Change

[lbowroom]

Only dangerous if you let it. I don’t understand why you would ever let it drop that far down, just to prove a point? Use your right foot as intended and set the correct speed for the circumstance with it. It’s not autonomous.

 

[john5520]

Well, today on the way home I got 0 phantom braking on the freeway. It was smooth sailing all the way. I did keep the car in the center lane, so that could be contributing factor. The speed limit was still off but didn't seem to matter (saying 45 in a 55) like before.

 

[thewishmaster]

So it only happens on those areas and not in other areas?

For me, generally yes. I've never really had the case of wrong speed limit being picked up on the freeway, only these speed changes unrelated to the speed limit.

 

[cruiserlarry]

Just for reference - still occurring, even after 2020.12.5....hello, Tesla

 

[ElectroFish]

Only dangerous if you let it. I don’t understand why you would ever let it drop that far down, just to prove a point? Use your right foot as intended and set the correct speed for the circumstance with it. It’s not autonomous.

I never said I would let it go from 75 to 45 mph . I was saying the cruise control switches from 75 to 45 and it just randomly hits the brakes hard. When it does I junp on the throttle and cancel it out .

 

[mpcookson]

I never said I would let it go from 75 to 45 mph . I was saying the cruise control switches from 75 to 45 and it just randomly hits the brakes hard. When it does I junp on the throttle and cancel it out .

This happens to me so often, because I'm driving in the right lane, because I'm doing the speed limit. It happens so often that I bought a GoPro to record my trips so that I could show it to Tesla. Probably happened a dozen times last week. I sent them a couple of videos and they checked the car's logs. They say that the car is using GPS and "fleet" data to figure speed and that there's nothing wrong with my specific car that could be fixed. There's no way anyone in the fleet is doing 45mph on I-90!

I'm driving without autopilot, just cruise control. The cruise "max" setting goes from 73 (where I set it, on a 70MPH road -- adjusting for slightly smaller tires, radar speed signs say I'm doing 71 or 72 at a Tesla indicated 73) to 45mph instantly. You see the little blue arc redraw, and max regen happens immediately. I then jump on the throttle and passengers freak out because of the whiplash.

I contend this is a dangerous bug and that someone needs to learn how to validate inputs. If the cruise is set for 73, the speed limit sign says 70 MPH, should you really go to a max of 45 MPH in one jump without anyone turning the thumbwheel? The answer is an emphatic "no".

This happens to me often while driving around St. Paul MN and a lot while driving from St. Paul to Dayton OH. It never happens when the speed limit changes on the freeway -- I can go from a 70MPH zone to a 55MPH zone without it adjusting a thing. I can understand (but don't like) it slowing for off ramps, but it shouldn't allow for a change of this magnitude when the speed limit hasn't also changed (and probably even then since it's unlikely that anyone following me is expecting me to jumping on the brakes right at the sign). Is there any place that actually has a 70MPH speed limit that butts up to a 45MPH speed limit?

 

[primedive]

This is still happening in 2023. My set speed will change from 100 down to 70, 50, or even 40 km/h (25mph) on the highway! It always happens at the same spots. Pressing the accelerator stops the braking but the set speed never goes back to the previous setting. This makes auto steer more stressful than just driving by myself and is dangerous.

 

[clydeiii]

This is still happening in 2023. My set speed will change from 100 down to 70, 50, or even 40 km/h (25mph) on the highway! It always happens at the same spots. Pressing the accelerator stops the braking but the set speed never goes back to the previous setting. This makes auto steer more stressful than just driving by myself and is dangerous.

If you know where it happens, you get ready for the change and flick up on the wheel the moment it happens and it will return to previous speed. No need to hit acceleration pedal.

 

[Padelford]

This happened to me yesterday afternoon on I-5 southbound at the southernmost Marysville WA exit. FSD beta 11.3.6 active. I was in the left lane at 60+ MPH and in dense traffic flow when the vehicle suddenly hit the brakes. I stomped on the accelerator and resumed speed. This has happened at that spot before.

 

[SidetrackedSue]

If you know where it happens, you get ready for the change and flick up on the wheel the moment it happens and it will return to previous speed. No need to hit acceleration pedal.

The other poster knows it happens in particular spots. But taking the car a place one isn't familiar with means at any time the car could have that same rapid deacceleration for no reason. Thus driving in AP or FSDv becomes stressful because you can't get ready for a change you have no idea will happen.

 

[clydeiii]

The other poster knows it happens in particular spots. But taking the car a place one isn't familiar with means at any time the car could have that same rapid deacceleration for no reason. Thus driving in AP or FSDv becomes stressful because you can't get ready for a change you have no idea will happen.

Driving in new areas also stressful. Reacting to other drivers is stressful. I pay attention very closely to what the car is doing and what others are doing and react accordingly.

 

[primedive]

If you know where it happens, you get ready for the change and flick up on the wheel the moment it happens and it will return to previous speed. No need to hit acceleration pedal.

I tried this and it seems to work about half of the time -- thanks! The other half, it refuses to raise the limit and I end up having to switch it off completely.

 

[Occhis]

Driving in new areas also stressful. Reacting to other drivers is stressful. I pay attention very closely to what the car is doing and what others are doing and react accordingly.

I use it as an extra set of eyes, being as attentive as if not using it. On a busy road it’s added insurance to avoid rear-ending someone during those moments when you’re checking the rear view or looking to one side.

 

[Genie]

My slow-downs seem more random, except for 1 spot where it thinks the speed limit dropped to 25mph (it doesn’t and never has) but only when I am eastbound, it has never happened coming back. At least it’s not a surprise like the random slowdowns on highways.

Of course I know to override with the pedal but this is a BS thing to have to do and negates any relaxation I get from the ADAS.

 

[JB47394]

My slow-downs seem more random, except for 1 spot where it thinks the speed limit dropped to 25mph (it doesn’t and never has) but only when I am eastbound, it has never happened coming back. At least it’s not a surprise like the random slowdowns on highways.

Of course I know to override with the pedal but this is a BS thing to have to do and negates any relaxation I get from the ADAS.

Is there any chance that there's a 25mph residential road adjacent to the highway that the car is interpreting as your current road because the GPS position is very slightly off?

 

[Genie]

Is there any chance that there's a 25mph residential road adjacent to the highway that the car is interpreting as your current road because the GPS position is very slightly off?

No, I know this area very well and this is not a proximity problem. The car thinks the limit dropped from 35-25 for about 1/2 mile when I’m eastbound only. The area is woods and farms, the lowest limit around here is 35.

 

[Occhis]

Cameras will pick up speed limit signs on adjacent roads. Happens often when in local lanes on interstate and car shows speed limit for the express lanes when the local and express are side by side.

 

[DrMaxine]

Happened to me too. First longish trip in my model Y with FSDb from Dallas to San Antonio . On the highway with a 75 mph limit it suddenly decided the limit was 45. Also when there are amber lights across the highway it thinks it needs to stop. Needless to say I didn’t use FSD much. Had to disable it in order to avoid an accident.