Phantom braking when a car is following you.

[Kablooie]

Near my house is a spot on a 45 MPH highway where 10.69.2.2 always puts on the brakes, hard. It almost comes to a stop before picking up speed again. I've reported it multiple times.

Today there was a car behind me for the first time.
When I reached the phantom braking spot, instead of slowing down, the car flew through without any hesitation at all.

This indicates that the car takes into account if there is a car following you. It modifies it's braking behavior if it might cause an accident.
This could be the reason there have been no reports of anyone being rear ended because of phantom braking. (At least none I'm aware of.)

It's good that it avoids causing an accident but doubly frustrating that it still phantom brakes at locations where it seems to know it doesn't have to.

 

[redmunds]

That's interesting, but a single data point doesn't hold up statistically. Maybe try a few more times with someone you know following you.

 

[Dewg]

Further testing is needed to confirm this - as correlation does not equal causation. This could have been a coincidence.

 

[DarkForest]

Interesting hypothesis! I wonder if that’s why some people (almost) never experience phantom braking.

Now that I know to look for this, I’ll keep track of it when my car unexpectedly doesn’t phantom brake. I know it definitely helps if someone’s in front of you, but I never thought to check if someone was behind me.

 

[joeyboy_m]

Speaking to this subject today i was headed home doing 75 and being tailgated and a car on the side of the road caused it to phantom break luckily I was ready to hit the accelerator but not before making the truck behind me lock it up. And then it did the stupid thing where everytime i let off the acceleration it slows down even though i was well below my set point. Im sure that guy thought i was trying to cause him to rear end me. Cause its definitely what it looked like. Then it got me wondering who would be at fault if he did hit me. He wad definitely following to close. But on camera it would look like i break checked him.

 

[clydeiii]

Near my house is a spot on a 45 MPH highway where 10.69.2.2 always puts on the brakes, hard. It almost comes to a stop before picking up speed again. I've reported it multiple times.

Today there was a car behind me for the first time.
When I reached the phantom braking spot, instead of slowing down, the car flew through without any hesitation at all.

This indicates that the car takes into account if there is a car following you. It modifies it's braking behavior if it might cause an accident.
This could be the reason there have been no reports of anyone being rear ended because of phantom braking. (At least none I'm aware of.)

It's good that it avoids causing an accident but doubly frustrating that it still phantom brakes at locations where it seems to know it doesn't have to.

Doesn't sound like PB. Sounds like bad map data, where it thinks there is a good reason to stop (used to be a stop sign or light). Just take over since you can predict. It's what I do.

 

[RickHevia]

Near my house is a spot on a 45 MPH highway where 10.69.2.2 always puts on the brakes, hard. It almost comes to a stop before picking up speed again. I've reported it multiple times.

Today there was a car behind me for the first time.
When I reached the phantom braking spot, instead of slowing down, the car flew through without any hesitation at all.

This indicates that the car takes into account if there is a car following you. It modifies it's braking behavior if it might cause an accident.
This could be the reason there have been no reports of anyone being rear ended because of phantom braking. (At least none I'm aware of.)

It's good that it avoids causing an accident but doubly frustrating that it still phantom brakes at locations where it seems to know it doesn't have to.

I've been experiencing that same random braking on my 2021 Model 3, and, yes, I almost got rear ended at 65 mph. The car that almost rearended me ended up in a ditch trying to avoid me. I have to believe that this is a camera/algorithm problem. I am a new member of this community, so I don't know the status of this problem and if Tesla is doing anything about it. I had a breaking incident as recently as yesterday. I have mostly stopped using it. There's no way I'm paying $10K for full auto pilot if basic cruise control is this bad.

 

[DCGOO]

I've been experiencing that same random braking on my 2021 Model 3, and, yes, I almost got rear ended at 65 mph. The car that almost rearended me ended up in a ditch trying to avoid me. I have to believe that this is a camera/algorithm problem. I am a new member of this community, so I don't know the status of this problem and if Tesla is doing anything about it. I had a breaking incident as recently as yesterday. I have mostly stopped using it. There's no way I'm paying $10K for full auto pilot if basic cruise control is this bad.

Unfortunately, there is not much Tesla can do about the knucklehead behind you, that was not paying attention.

 

[nvx1977]

The entire premise of this thread makes no sense.

It implies that the car knows that it's braking unnecessarily and will choose not to brake because of the possibility of a rear-end collision. So why brake unnecessarily in the first place?

the car would need to be prioritizing collision risks. That could be possible, but in what situation would a car prioritize avoiding a rear collision (one that isn't even guaranteed due to the unknown faculty of the following driver) over a frontal collision, real or perceived?

correlation does not imply causation. there could be another variable you aren't aware of that caused that behavior that day. We all know FSDb is well-known for being inconsistent. It doesn't require a tailing car for FSDb to suddenly do something it never did before.

 

[Kablooie]

The entire premise of this thread makes no sense.

It implies that the car knows that it's braking unnecessarily and will choose not to brake because of the possibility of a rear-end collision. So why brake unnecessarily in the first place?

the car would need to be prioritizing collision risks. That could be possible, but in what situation would a car prioritize avoiding a rear collision (one that isn't even guaranteed due to the unknown faculty of the following driver) over a frontal collision, real or perceived?

correlation does not imply causation. there could be another variable you aren't aware of that caused that behavior that day. We all know FSDb is well-known for being inconsistent. It doesn't require a tailing car for FSDb to suddenly do something it never did before.

I’ve noticed the same thing. There is a non standard lane turn divider near me that the car always slows down for. If a car is fairly close behind me it doesn’t slow down. I assume it has priorities as to behavior and a car close behind is a higher priority than figuring out a new kind of turning divider ahead.

 

[kabin]

Near my house is a spot on a 45 MPH highway where 10.69.2.2 always puts on the brakes, hard. It almost comes to a stop before picking up speed again. I've reported it multiple times.

Today there was a car behind me for the first time.
When I reached the phantom braking spot, instead of slowing down, the car flew through without any hesitation at all.

This indicates that the car takes into account if there is a car following you. It modifies it's braking behavior if it might cause an accident.
This could be the reason there have been no reports of anyone being rear ended because of phantom braking. (At least none I'm aware of.)

It's good that it avoids causing an accident but doubly frustrating that it still phantom brakes at locations where it seems to know it doesn't have to.

I've recently wonder the same. I've got two locations with 1/10 mile separation and phantom braking always happens. Recently a car was matching my speed in the adjacent lane and I didn't experience phantom braking! There's many FSDb quirks so it's hard to rule anything out.

 

[Alex10000]

Just to clarify, are PB incidents mostly or only happening to people on cruise control?

 

[2101Guy]

Just to clarify, are PB incidents mostly or only happening to people on cruise control?

Best description of FSD yet.

And yes

 

[2101Guy]

Doesn't sound like PB. Sounds like bad map data, where it thinks there is a good reason to stop (used to be a stop sign or light). Just take over since you can predict. It's what I do.

To a customer…it’s phantom braking. We must stop making excuses for poor performance situations.

 

[rt29781]

We sold our M3 SR+ in November because of phantom braking. We bought a Honda Civic and it has ACC which works perfectly.

 

[gsmith123]

The entire premise of this thread makes no sense.

It implies that the car knows that it's braking unnecessarily and will choose not to brake because of the possibility of a rear-end collision. So why brake unnecessarily in the first place?

the car would need to be prioritizing collision risks. That could be possible, but in what situation would a car prioritize avoiding a rear collision (one that isn't even guaranteed due to the unknown faculty of the following driver) over a frontal collision, real or perceived?

correlation does not imply causation. there could be another variable you aren't aware of that caused that behavior that day. We all know FSDb is well-known for being inconsistent. It doesn't require a tailing car for FSDb to suddenly do something it never did before.

Sound logic, although anecdotally I've seen the car slow down less when being followed too... Unfortunately this is a hard thing to test in a controlled way.

 

[Jarends]

My 2019 X, has gotten worse after the last update. No mirage, clear ahead.
Once with someone behind me forcing them into the left lane, must have thought I break checked them. Passed me, giving me a look like I was a complete idiot. It's embarrassing.

 

[nurusz]

Near my house is a spot on a 45 MPH highway where 10.69.2.2 always puts on the brakes, hard. It almost comes to a stop before picking up speed again. I've reported it multiple times.

Today there was a car behind me for the first time.
When I reached the phantom braking spot, instead of slowing down, the car flew through without any hesitation at all.

This indicates that the car takes into account if there is a car following you. It modifies it's braking behavior if it might cause an accident.
This could be the reason there have been no reports of anyone being rear ended because of phantom braking. (At least none I'm aware of.)

It's good that it avoids causing an accident but doubly frustrating that it still phantom brakes at locations where it seems to know it doesn't have to.

I don't think that FSD take into account what is more dangerous to be rear-ended or to collide with a moving vehicle traveling in front of you?

 

[JB47394]

I don't think that FSD take into account what is more dangerous to be rear-ended or to collide with a moving vehicle traveling in front of you?

It distinguishes based on liability. If the choice is to hit or be hit, the car will choose to be hit every time. In the US, the liability is on the driver that hits the vehicle in front of it - for following too close. So if the Tesla rear ends a car, the Tesla driver is liable. If the Tesla is rear ended, the other driver is liable. Phantom braking is a result of false positives and an abundance of caution.

 

[nurusz]

I think the importance is the risk on the Tesla driver and not who is liable for the accident !