Abrupt Phantom Breaking at high speed - scary

[legendsk]

Given the ghosts that appear when my Y is parked in my carport, (semi's, pedestrians, motorcycles, etc.), I suspect it likely phantom brakes, even parked. But if it is in 'P', it's a little hard to tell. I know for sure it will phantom brake driving with absolutely everything possible turned off. Once it even shifted into 'P' when it did a PB, but I believe that was just because it stopped so abruptly it threw both the passenger and me forward so hard against the seat belts, the seat sensors likely reported that the driver and passenger had exited the vehicle? {I normally keep the seat belts a bit loose, relying on the car to snug them up prior to a crash when it senses there is going to be a crash.}

 

[SkinnyCarGuy]

It's called FSD Supervised, you should drive watching the road, hand of the steering wheel and a foot ready to press the brake or accelerator at all times. The fact that you went from 80 MPH to 40 MPH without taking corrective action speaks volumes, you're the driver. No need to turn off auto pilot, just press on the accelerator, you might loose 4 or 5 MPH max. It's really not fair to others on the road that you didn't take corrective action immediately.

Besides the items listed above, sometimes this is caused by missing or poorly marked traffic lanes.

I was watching the road. It happened in the blink of an eye, and I took corrective action as quickly as I could. Thanks

 

[texas_star_TM3]

That would explain it. Incorrect speed sign detection may cause it, especially in FSD where there is a city driving mode (different from AP which is expected to be driven at higher speeds).

yeah. only because a speed sign shows up doesn't justify braking super hard to hit that posted speed within seconds....

 

[texas_star_TM3]

It's called FSD Supervised, you should drive watching the road, hand of the steering wheel and a foot ready to press the brake or accelerator at all times. The fact that you went from 80 MPH to 40 MPH without taking corrective action speaks volumes, you're the driver. No need to turn off auto pilot, just press on the accelerator, you might loose 4 or 5 MPH max. It's really not fair to others on the road that you didn't take corrective action immediately.

Besides the items listed above, sometimes this is caused by missing or poorly marked traffic lanes.

because hitting the accelerator hard when the car brakes is a pretty novel thing to do.... it's completely counterintuitive

 

[stopcrazypp]

yeah. only because a speed sign shows up doesn't justify braking super hard to hit that posted speed within seconds....

There was a recall forced by the NHTSA to react faster to speed limit changes. Whatever heuristics/training it had previously to smooth things out was probably removed.

Also V12 added the speed adjustment which likely uses traffic flow to figure out the appropriate speed. When there is no traffic (as OP is saying) it has no traffic flow to judge on, so it would probably rely much more on the speed sign.

The other factor is there is much less risk to brake when there is no traffic.

 

[enemji]

I recently purchased a 2022 Model 3 Performance that had about 10,000 miles on it and had been owned by two previous owners. I had been enjoying the car until the other night, when I experienced a braking incident while driving at 80 mph on the highway using FSD (latest update).

Scene:
- Nighttime on a dark highway
- I don't remember seeing an overpass

I was using FSD, relaxing and watching the road, when suddenly the car slammed on the brakes. The speed dropped to 40 mph before I disengaged the FSD and sped back up. My passengers were horrified, and if there had been a car behind us, we would have been in serious trouble.

Why did this happen, and how can I prevent this in the future?

Can you describe it more? Were you alone on the road, or were there any vehicles in the visible range?

 

[SkinnyCarGuy]

Can you describe it more? Were you alone on the road, or were there any vehicles in the visible range?

I was alone on the road.

 

[SkinnyCarGuy]

because hitting the accelerator hard when the car brakes is a pretty novel thing to do.... it's completely counterintuitive

even more so to a brand new tesla user

 

[enemji]

I was alone on the road.

That is very helpful data point. So far every PB has been experienced when no other vehicle is in visible range. That point very clearly to the reference aspect I wrote earlier. It is like navigating using the stars but when it is a cloudy night, the ships are stuck and anchor ️ ahoy is issued!

 

[texas_star_TM3]

There was a recall forced by the NHTSA to react faster to speed limit changes. Whatever heuristics/training it had previously to smooth things out was probably removed.

funny how dozens of other manufacturers achieve speed limit sign automated reading without the car going from 70 mph to 50 mph in seconds. if that's the real cause for PB... which it isn't...

 

[enemji]

There was a recall forced by the NHTSA to react faster to speed limit changes. Whatever heuristics/training it had previously to smooth things out was probably removed.

I once got a speeding ticket for not reducing my speed from 45 to 30 over an intersection. On one side of the traffic light is 45mph, the other side is 30mph. Bloody cops expecting me to do PB on my own while passing under a traffic light.

 

[stopcrazypp]

funny how dozens of other manufacturers achieve speed limit sign automated reading without the car going from 70 mph to 50 mph in seconds. if that's the real cause for PB... which it isn't...

Most of them are map based and/or have the same heuristics Tesla previously had (basically a limit for how much and how rapidly the speed can be reduced).

I'll give a concrete example, for example Ford's speed limiter system can't apply the brakes, it can only do engine braking. That drastically reduces the available deceleration.

Ford's New 'Speed Limiter' Can Regulate Driver's Speed

Depending on the point of view, Ford's new speed-limiting technology either helps lead foots curb their appetite for speed or represents a further intrusion on driver control and automotive privacy.

www.americanautomakers.org

However, when you use Blue Cruise, where it is allowed to use the brakes and it works based on sign detection, exactly the same thing happens:
"The truck will see a change in speed limit sign and harshly apply brake where maybe the speed limit dropped from 70 to 55 for a construction zone"

https://www.f150gen14.com/forum/threads/speed-limit-assist-is-annoying.11095/

NHTSA was specifically not happy with how Tesla's system responded to lower speed limits as part of the FSD investigation. Note the NHTSA does not universally apply findings to all manufacturers or to all systems. For example, Infiniti's earliest lane keeping system didn't have attention detection, but because it never got a NHTSA investigation it never had to add them.

And in a similar vein the same thing may not apply to vanilla AP. In some areas, there are some mapping errors, and AP would drop the set speed, but the car never applies the brakes, just applies some regen, which is easy to override with accelerator. Same for when set speed is much higher, it doesn't floor the accelerator, but applies a limited amount (such the sometimes I also override with accelerator).

As another pointed out right above, in some roads (especially construction zones that may not be mapped) to meet the reduced speed limit, you really actually have to apply the brakes. This is because by the time you see the sign, if you need to be below the speed posted, letting off the throttle is not enough. The only way to do a gradual slowdown is if you were aware of the limit before you see the sign (or there was a previous sign that warned of an approaching zone, which I'm not sure any system out there recognizes at the moment).

 

[texas_star_TM3]

Most of them are map based and/or have the same heuristics Tesla previously had (basically a limit for how much and how rapidly the speed can be reduced).

I'll give a concrete example, for example Ford's speed limiter system can't apply the brakes, it can only do engine braking. That drastically reduces the available deceleration.

Ford's New 'Speed Limiter' Can Regulate Driver's Speed

Depending on the point of view, Ford's new speed-limiting technology either helps lead foots curb their appetite for speed or represents a further intrusion on driver control and automotive privacy.

www.americanautomakers.org

However, when you use Blue Cruise, where it is allowed to use the brakes and it works based on sign detection, exactly the same thing happens:
"The truck will see a change in speed limit sign and harshly apply brake where maybe the speed limit dropped from 70 to 55 for a construction zone"

https://www.f150gen14.com/forum/threads/speed-limit-assist-is-annoying.11095/

NHTSA was specifically not happy with how Tesla's system responded to lower speed limits as part of the FSD investigation. Note the NHTSA does not universally apply findings to all manufacturers or to all systems. For example, Infiniti's earliest lane keeping system didn't have attention detection, but because it never got a NHTSA investigation it never had to add them.

And in a similar vein the same thing may not apply to vanilla AP. In some areas, there are some mapping errors, and AP would drop the set speed, but the car never applies the brakes, just applies some regen, which is easy to override with accelerator. Same for when set speed is much higher, it doesn't floor the accelerator, but applies a limited amount (such the sometimes I also override with accelerator).

As another pointed out right above, in some roads (especially construction zones that may not be mapped) to meet the reduced speed limit, you really actually have to apply the brakes. This is because by the time you see the sign, if you need to be below the speed posted, letting off the throttle is not enough. The only way to do a gradual slowdown is if you were aware of the limit before you see the sign (or there was a previous sign that warned of an approaching zone, which I'm not sure any system out there recognizes at the moment).

doesn't explain phantom braking in middle of nowhere, no speed signs changing.... i invite you to drive Dallas-Amarillo and onto Colorado via Clayton/NM on a hot sunny day. You will get PB's galore.... everytime the road has slight up/downs on long empty stretches with mirages over the asphalt. A real hoot going from 80 mph down to ~45 mph within seconds for no apparent reason.

 

[enemji]

doesn't explain phantom braking in middle of nowhere, no speed signs changing.... i invite you to drive Dallas-Amarillo and onto Colorado via Clayton/NM on a hot sunny day. You will get PB's galore.... everytime the road has slight up/downs on long empty stretches with mirages over the asphalt. A real hoot going from 80 mph down to ~45 mph within seconds for no apparent reason.

Been on that route and tons of PB when I was alone within the visible range. So is it Mirages or is it the fact that there is no referential data? Of course cellular signal was also very spotty. I am betting on No reference vehicles as well as spotty cellular GPS causing Anchor Ahoy to be issued

 

[stopcrazypp]

doesn't explain phantom braking in middle of nowhere, no speed signs changing.... i invite you to drive Dallas-Amarillo and onto Colorado via Clayton/NM on a hot sunny day. You will get PB's galore.... everytime the road has slight up/downs on long empty stretches with mirages over the asphalt. A real hoot going from 80 mph down to ~45 mph within seconds for no apparent reason.

In above I'm simply pointing out why the reaction to lower speed signs is the way it is and that when equivalent braking and sign based detection is used by other manufacturers, the same thing occurs for the same reason (they aren't immune to it either).

What you mention is a different, but related issue. With no traffic to reference traffic flow, and with lower risk of being rear ended, it likely reacts more dramatically to perceived danger.

 

[texas_star_TM3]

In above I'm simply pointing out why the reaction to lower speed signs is the way it is and that when equivalent braking and sign based detection is used by other manufacturers, the same thing occurs for the same reason (they aren't immune to it either).

What you mention is a different, but related issue. With no traffic to reference traffic flow, and with lower risk of being rear ended, it likely reacts more dramatically to perceived danger.

just give me radar back... so the car knows there is no "perceived danger" on a wide open highway .... the 1.2 MP cameras perceive danger differently than a radar unit. Or better: radar/Lidar and cameras

 

[texas_star_TM3]

Been on that route and tons of PB when I was alone within the visible range. So is it Mirages or is it the fact that there is no referential data? Of course cellular signal was also very spotty. I am betting on No reference vehicles as well as spotty cellular GPS causing Anchor Ahoy to be issued

either way it's totally unacceptable when other vehicles with TACC don't suffer from these issues and my Model 3 *before they deleted radar and forced it on vision only* had no issues on that road either. All i want is functioning TACC so i can rest my foot a bit without being paranoid of a PB every 5-10 minutes...