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Extreme phantom braking event tonight. No TACC or Autosteer

rjpjnk

Active Member
Mar 12, 2021
1,217
791
NJ
I've read a lot of posts about phantom braking but it never really concerned me much because up until today I had only experience minor and infrequent events.

Tonight, however, my car really scared me. It slammed on the brakes to the point that the wheels locked up slightly and the car fishtailed a bit to the left. I was not using either cruise control or Autosteer at the time. Just plain old fashioned driving by hand at 35 mph. It was dark, and a pickup truck was approaching in the opposite lane of a hilly two-lane country highway. We were on a straight portion of the road both heading down toward a low point, and just as the truck passed my Model Y slammed on the brakes and the system started beeping and screaming it's very loud alarm signal. Also an indication popped up on the screen that Dashcam footage was being saved.

Fortunately I was driving slowly and it was easy to regain control, but what the heck?!! That was bad! I assume it was the collision avoidance system that was responsible since TACC and AP were not in use. I believe I have only experience phantom braking when AP was active in the past so this seemed unusual. And I have never experienced braking this hard. Is this normal?

Since I know the exact timestamp and have dashcam footage do you think I should contact Tesla? I've watched the footage a few times and there is absolutely no reason I can see that collision avoidance should have been activated.

Car is a 2021 Vision Only Model Y LR.
 
I've read a lot of posts about phantom braking but it never really concerned me much because up until today I had only experience minor and infrequent events.

Tonight, however, my car really scared me. It slammed on the brakes to the point that the wheels locked up slightly and the car fishtailed a bit to the left. I was not using either cruise control or Autosteer at the time. Just plain old fashioned driving by hand at 35 mph. It was dark, and a pickup truck was approaching in the opposite lane of a hilly two-lane country highway. We were on a straight portion of the road both heading down toward a low point, and just as the truck passed my Model Y slammed on the brakes and the system started beeping and screaming it's very loud alarm signal. Also an indication popped up on the screen that Dashcam footage was being saved.

Fortunately I was driving slowly and it was easy to regain control, but what the heck?!! That was bad! I assume it was the collision avoidance system that was responsible since TACC and AP were not in use. I believe I have only experience phantom braking when AP was active in the past so this seemed unusual. And I have never experienced braking this hard. Is this normal?

Since I know the exact timestamp and have dashcam footage do you think I should contact Tesla? I've watched the footage a few times and there is absolutely no reason I can see that collision avoidance should have been activated.

Car is a 2021 Vision Only Model Y LR.
You should contact Tesla and the NHTSA. Phantom braking is a problem that has gone on too long.
 

glide

Active Member
Jun 6, 2018
4,751
6,593
USA
I've read a lot of posts about phantom braking but it never really concerned me much because up until today I had only experience minor and infrequent events.

Tonight, however, my car really scared me. It slammed on the brakes to the point that the wheels locked up slightly and the car fishtailed a bit to the left. I was not using either cruise control or Autosteer at the time. Just plain old fashioned driving by hand at 35 mph. It was dark, and a pickup truck was approaching in the opposite lane of a hilly two-lane country highway. We were on a straight portion of the road both heading down toward a low point, and just as the truck passed my Model Y slammed on the brakes and the system started beeping and screaming it's very loud alarm signal. Also an indication popped up on the screen that Dashcam footage was being saved.

Fortunately I was driving slowly and it was easy to regain control, but what the heck?!! That was bad! I assume it was the collision avoidance system that was responsible since TACC and AP were not in use. I believe I have only experience phantom braking when AP was active in the past so this seemed unusual. And I have never experienced braking this hard. Is this normal?

Since I know the exact timestamp and have dashcam footage do you think I should contact Tesla? I've watched the footage a few times and there is absolutely no reason I can see that collision avoidance should have been activated.

Car is a 2021 Vision Only Model Y LR.
What you described is not phantom braking. It’s collision avoidance.
 

rjpjnk

Active Member
Mar 12, 2021
1,217
791
NJ
That's what I am considering as well. I like the idea that the car can intervene and potentially avoid a collision, but apparently it can be dangerous it it gets it wrong.

This was a false alarm since there was never any real danger of collision. Problem is, the evasive action taken by the car might actually have caused a collision in other circumstances. If I wasn't holding the wheel I might not have been able to immediately take over and right the car back into my lane, and what if another car was behind me? I really want Tesla to have the logs for this event so they can figure out what went wrong and help it to not happen again.

I am going to go see what settings I have active and report back.
 

rjpjnk

Active Member
Mar 12, 2021
1,217
791
NJ
What you described is not phantom braking. It’s collision avoidance.
I always thought that anytime the car applied the brakes unnecessarily it was called phantom braking as tha_ape said. However, it is important to distinguish that this particular situation occurred without any TACC or Autosteer or FSD active, so perhaps it should be called phantom collision avoidance?

How does CA work, and is it different in the vision-only cars?

Also, is CA the same as AEB (automatic emergency braking)? I guess I thought collision avoidance involved controlling the steering.
 

glide

Active Member
Jun 6, 2018
4,751
6,593
USA
Braking when not needed is what people refer to as "Phantom Braking". Whatever system caused it is immaterial.
Not true. In this case, the vehicle was attempting to avoid, what it thought was a potential collision, with another oncoming vehicle.

Phantom braking happens when there is seemingly nothing in front of you. Like a shadow from an overpass.
 

rjpjnk

Active Member
Mar 12, 2021
1,217
791
NJ
So here are the settings I was using. On the Autopilot screen:
Forward collision warning = Medium
Land departure avoidance = Warning
Emergency lane departure avoidance = On
Blind spot collision warning chime = On
Automatic emergency braking =On
Obstacle aware acceleration = On

So I am guessing it was the AEB that I experienced. Seems weird given nothing was in my lane and it was a straight stretch of highway.
 
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For me it's Phantom Braking. In general systemic Phantom Braking results from a misinterpreted approaching object, shadow, glare, roadway rubber skid mark, video noise, or even software bug. In these cases a collision threat doesn't exist in any real world driving sense and yet the software commanded vehicle braking to avoid serious harm from the Phantom threat.
 
So here are the settings I was using. On the Autopilot screen:
Forward collision warning = Medium
Land departure avoidance = Warning
Emergency lane departure avoidance = On
Blind spot collision warning chime = On
Automatic emergency braking =On
Obstacle aware acceleration = On

So I am guessing it was the AEB that I experienced. Seems weird given nothing was in my lane and it was a straight stretch of highway.

Unfortunately, unless you disable AEB the unreliable video data will always result in Phantom Braking.
 
So here are the settings I was using. On the Autopilot screen:
Forward collision warning = Medium
Land departure avoidance = Warning
Emergency lane departure avoidance = On
Blind spot collision warning chime = On
Automatic emergency braking =On
Obstacle aware acceleration = On

So I am guessing it was the AEB that I experienced. Seems weird given nothing was in my lane and it was a straight stretch of highway.

When you look at the saved video do you see any shadows or sunlight reflections from the vehicle as it approaches/passes? Where was the sun in relation to your vehicle and the passing object?
 
Hello Everyone,

greets from Ontario.

regarding the phantom braking apperances, I have to join the subject. I have a 2022 M3LR, received last saturday 18. Dec. 2021.
Yesterday evening , I was driving the route London, ON to Toronto Airport and back on the 401 Highway. The complete drive was after sunset. The set speed in cruise control only (110 to 120 kmh) , without autosteering. I do not have FSD.

The phantom braking did appear really out of the blue cruising with 110kmh when getting close to off-ramps, being on the most right snail lane. It appears, as if the car sees the speed limit signs at the off ramp and tries to obey. I do not think the brakes were applied, but the energy recovery braking slowed the car down from 110 to 90, even the cruise control was changed to the setting of 80 kmph.
I believe, the auto AEB, as described in the previous mesage from rjpjink was set on as well.
I do have the FSD auto recognition activated though.

The auto steering, I guess its called here Autopilot (beta) was not activated as the feature does activate the high beams in a erratic fashion, which does not comply with my high beam behaviour, being more moderate with it. I really do not understand the matter behind this kind of operational need to take over the high beams for the auto pilot option. Is the car blind at night to operate to have the need for the high beams with this ?
 
We picked up our M3LR on Friday (Dec 17). We were driving home on Saturday on rural Texas roads using cruise control when we had a huge braking event when a semi truck was approaching in the opposite lane. It was pretty scary. It actually happened a few times. There were no issues when we were on divided highways with multiple lanes but only on those single lane roads.
We are not sure what adjustments need to be made to lessen the chances of this happening again. Suggestions?
 

Big Earl

bnkwupt
Supporting Member
Jul 12, 2017
6,861
13,477
Springfield, VA
For me it's Phantom Braking. In general systemic Phantom Braking results from a misinterpreted approaching object, shadow, glare, roadway rubber skid mark, video noise, or even software bug. In these cases a collision threat doesn't exist in any real world driving sense and yet the software commanded vehicle braking to avoid serious harm from the Phantom threat.

There's an important distinction between a false collision avoidance and run-of-the-mill phantom braking. The former sounds the collision avoidance alarm and the latter does not. The former evokes a maximum braking response while the latter is less aggressive. With collision avoidance, the vehicle has a very high degree of certainty that it is going to collide with another object. With the more common phantom braking, the vehicle is receiving conflicting information from sensors (e.g., a mismatch between vision and radar, obstructed view of the path ahead, etc.) and is less sure of the path ahead, resulting in less-than-maximum deceleration.

There's also a third type of phantom braking where the vehicle slows down due to erroneous speed limit changes, typically caused by road construction changing road alignment.

Fixing bugs, software and hardware problems is more difficult when you use general terminology to describe specific problems. It doesn't take much extra effort to be more specific when describing problems.
 

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