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Phantom Braking

JamesO43

New Member
Aug 12, 2020
1
0
Chicago
Does anyone have a problem with Phantom Braking? I've had problems with this since I bought my Model S 2019 a year ago. The car will suddenly hit the brakes hard when I am in cruise control. It has happened several times on the highway when I was going fast, 70 yo 75 and slowed me quickly to 55 or so. Had the roads been wet, I fear I could have had an accident. I took it in to the service facility and they said they were unable to replicate the problem. Any help would be appreciated. JamesO43
 
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Tam

Well-Known Member
Nov 25, 2012
9,737
8,886
Visalia, CA
...unable to replicate the problem...

Hi James:

It can be replicated and it's a well-known problem for any system that depends on RADAR.

In the Uber Autonomous Vehicle fatality, its engineers tried to solve the phantom braking by disabling the system (It didn't utilize RADAR in this case then there's no phantom braking from the system which also lead to the death of the pedestrian).

Report: Uber self-driving team was preparing for CEO demo before fatal crash

The replicated scenarios:

1) A car in front just turns left or right.

2) A car just pulls out in front of you from an intersection or driveway.

3) An overpass bridge...

Remedy:

1) You just need to pay attention to which scenario that leads to Phantom Brakes and it might just be a certain repeatable spot/location during your drive so you can be ready to press on the accelerator.

2) LIDAR as the primary sensor instead of RADAR.

3) TeslaVision will "soon" (as in years or decades?) be working as the primary sensor instead of the current RADAR to brake for obstacles.
 

cookie99

Member
Mar 14, 2016
911
500
California
Does anyone have a problem with Phantom Braking? I've had problems with this since I bought my Model S 2019 a year ago. The car will suddenly hit the brakes hard when I am in cruise control. It has happened several times on the highway when I was going fast, 70 yo 75 and slowed me quickly to 55 or so. Had the roads been wet, I fear I could have had an accident. I took it in to the service facility and they said they were unable to replicate the problem. Any help would be appreciated. JamesO43

a quick search online will show this is just 1 out of the 100 posts on this topic. we're probably at 1 a month now.
 

Wol747

Active Member
Aug 26, 2017
1,158
613
Tea Gardens
>>maybe it picks up the speed limit. watch the GPS speed limit in the display<<

No. as I said, no signs. And in any case it almost immediately picks up the speed as set unless I have already disconnected the A/P.
All suggestions demonstrate the fundamental issue - and IMHO the legal problem - we are using a very complex bit of kit on public roads as experimenters but have little or no idea how it works or what its parameters are - especially when it updates all the time.
Autonomous driving is arguably more complex than an aircraft autopilot system yet the pilots operating the latter have by law to understand the workings of the modes, the failure modes etc etc.
I've said it before but the hubris - of all the companies working on autonomous driving - is staggering. I can see huge legal issues if it ever becomes mainstream on "normal" public areas.
 

Altes

Member
Sep 30, 2016
646
554
SF Bay area

upload_2020-8-13_18-56-57.png
 

emmz0r

Senior Software Engineer
Jul 12, 2018
1,266
1,109
Norway
>>maybe it picks up the speed limit. watch the GPS speed limit in the display<<

No. as I said, no signs. And in any case it almost immediately picks up the speed as set unless I have already disconnected the A/P.
All suggestions demonstrate the fundamental issue - and IMHO the legal problem - we are using a very complex bit of kit on public roads as experimenters but have little or no idea how it works or what its parameters are - especially when it updates all the time.
Autonomous driving is arguably more complex than an aircraft autopilot system yet the pilots operating the latter have by law to understand the workings of the modes, the failure modes etc etc.
I've said it before but the hubris - of all the companies working on autonomous driving - is staggering. I can see huge legal issues if it ever becomes mainstream on "normal" public areas.

I am not talking about the physical signs but the reported speed limit in the display
 

Aerieudite

Member
Sep 1, 2019
12
7
Austin
Mine consistently brakes on the freeway where another road goes off: no signs, no road markings, no traffic. No brains....

One common and consistent cause of undesired sudden braking seems related to the Autopilot Speed Limit "relative" setting. Ours is set to Relative = +6 mph, reasonable under most conditions. When engaged, cruise control immediate accelerates to 6 mph over the speed limit (unless slower traffic ahead). But traffic flow on many freeways is 10-15 mph over the posted limit at off-peak times. So when cruise control is engaged the car initially accelerates to 71 mph (in a 65 zone), and must be manually bumped up if a higher cruising speed is desired.

"Phantom" or undesired braking can occur when transitioning to a new freeway, even where the speed limits for both freeways are the same, if the cruise speed was set to something other than posted + relative (65 + 6 = 71). Apparently Auto Pilot sees it as a "new" speed limit, and resets cruise speed to Speed Limit + Relative. If cruising faster, the car brakes aggressively down to 71 mph. It happens so consistently in some spots that I've learned to expect it and just bump the speed back up to the desired setting. But it's certainly annoying, both to me and any drivers behind.

I haven't figured out a good way around this. I could set Auto Pilot Speed Limit / Relative higher, maybe to +15. When engaged in light traffic, the vehicle would accelerate to 80 in a 65 zone. But it would also accelerate to 55 in a 40 mph zone, which is almost certainly undesirable. I suspect it would also ACCELERATE to 80 mph if cruising at less than 80 mph and transitioning to a new freeway. Anyone know for sure?

There's apparently no way to disable the Speed Limit feature; the only choices are Relative or Absolute. Neither is good in all cases, but Relative seems generally better. Maybe have 2 Speed Limit settings, one for freeways and another for surface streets. OR, allow a relative percent or "factor" instead of just mph/kph. A relative factor of 1.15 would accelerate the car to 75 in a 65 zone, but only to 46 in a 40 mph zone. Still not perfect, but better, although people with social science degrees would have to do math, and the vehicle would still accelerate or decelerate when the speed limit changes (good) or when transitioning to another freeway/autobahn, etc (usually not good). This may be one of those problems to which there is no good solution.

And while I do observe THIS phenomena predictably, it's clearly not the only cause of phantom braking, just the most consistent.
 
Driving down the Interstate at 75mph on AutoPilot, the car braked HARD with no obstruction in front of me. My guess is that it was reacting to a dark shadow of an overpass. I was very fortunate nobody was behind me or I very well might have been rear-ended.

I've had my car less than 2 weeks and this is the 2nd time it's slammed on the brakes for no valid reason. Once was on a 35mph road where I think it freaked out about a car in the other lane as I rounded a curve -- it probably thought I was going to hit it although we were both perfectly within our lanes. And now this.

I am not impressed.

Software v10.2 (2020.40.4.5)
 
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Reactions: Watts_Up
Driving down the Interstate at 75mph on AutoPilot, the car braked HARD with no obstruction in front of me. My guess is that it was reacting to a dark shadow of an overpass. I was very fortunate nobody was behind me or I very well might have been rear-ended.

I've had my car less than 2 weeks and this is the 2nd time it's slammed on the brakes for no valid reason. Once was on a 35mph road where I think it freaked out about a car in the other lane as I rounded a curve -- it probably thought I was going to hit it although we were both perfectly within our lanes. And now this.

I am not impressed.

Software v10.2 (2020.40.4.5)
Had this happen on the N.Y. turnpike with a semi travelling behind me, happened other times but this was the worst of them. As soon as the semi appeared to get very close my car speed up.
Shadow from overpass on a very sunny day. This was last year. Has never been that scary again. Autopilot will improve when beta fsd goes wide. Some of the fsd software will make it's way down to plain old AP.
 

BigNick

Infamous Fat Sweaty Guy
Dec 3, 2017
1,467
1,696
Pennsylvania, USA
AP1 is still better at minimizing phantom braking compared to AP2+ versions.

The problem with phantom braking is that you have to “cover” the accelerator pedal to react to it, instead of covering the brake pedal as with normal cruise control. This slows your reaction if braking is needed but the AP is late to brake or just doesn’t “see” a legitimate obstacle (animal in road, etc.)
 
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Reactions: idoco
The worst thing about this IMO is that I cannot even use "regular old cruise control" without stressing about this. Unless there is some way to activate cruise without the "traffic aware" part.

So I have supposedly the most advanced self-driving vehicle on the market and I cannot rely on the oldest and most basic driving aid.
 

BigNick

Infamous Fat Sweaty Guy
Dec 3, 2017
1,467
1,696
Pennsylvania, USA
The worst thing about this IMO is that I cannot even use "regular old cruise control" without stressing about this. Unless there is some way to activate cruise without the "traffic aware" part.

So I have supposedly the most advanced self-driving vehicle on the market and I cannot rely on the oldest and most basic driving aid.
Tesla does not give the option for "regular" cruise control (as far as I've been able to tell on my AP1 car) on autopilot-equippred cars. It's TACC or manual.
Interestingly enough, my wife's new ICEr allows the driver to choose either standard or adaptive cruise control mode. Although the adaptive mode uses only a camera - there is no grille-mounted radar.
 
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Reactions: COS Blue

Wol747

Active Member
Aug 26, 2017
1,158
613
Tea Gardens
I for the life of me cannot understand why it seems to get worse with each update (as many experience.).
I had two serious ones as well as several "soft" ones yesterday in a 20Km drive to check my tyre pressure indications. Soft one feel as if I've half lifted off the accelerator (regen ) but the two baddies were full on braking. Six months ago I rarely had other than softies (which still put the wind up the Mrs.)
 

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