Phantom Braking Measured

[JasonCinOtt]

Phantom braking is a problem.

With 15K miles logged in the last year and a daily commute of only about 15 miles round trip, I have taken many long trips with EAP engaged. Phantom braking is so scary for me at highway speeds that I change my driving behavior. If traffic is tailing me too closely, I will either pull over to the next lane or disengage EAP. I am very concerned about getting rear ended at 79 MPH when the Phantom Braking happens when a tailgating driver doesn’t expect the vehicle to reduce its speed by a bunch (15 mph?).

I report it EVERY SINGLE TIME by engaging the voice command and pushing that right scroll wheel and saying “Bug Report - Phantom Braking.” I encourage everyone to do the same.

This issue is probably my biggest gripe with my Tesla.

Didn't know about the bug report ability...now that I know that I will be using it ... alot. I have multiple phantom braking issues every single trip. It's getting kinda ridiculous.

 

[Knightshade]

Didn't know about the bug report ability...now that I know that I will be using it ... alot. I have multiple phantom braking issues every single trip. It's getting kinda ridiculous.

Rumor has it all that feature does is essentially drop a "bookmark" in the log files so that a local service center can find it later if you bring the car in to them- but that it doesn't actually send anything to Tesla.

(and if you think about how many reports they'd need to manually review across a fleet of hundreds of thousands of cars making those reports that seems likely to be the case)

 

[JasonCinOtt]

Rumor has it all that feature does is essentially drop a "bookmark" in the log files so that a local service center can find it later if you bring the car in to them- but that it doesn't actually send anything to Tesla.

(and if you think about how many reports they'd need to manually review across a fleet of hundreds of thousands of cars making those reports that seems likely to be the case)

That's what I just read as well. At any rate, I will "bookmark" all of the events so eventually I can submit something that says "fix this". Still a great car though!

 

[Msjulie]

"Just awful"

Informative, no... and it is from the tailgating car AND it is from the driver and passengers who wonder WTF is happening here..

Forget it.. minds are made up already anyway..

 

[Wingsy]

I don't think it is.

Standard regen alone can do 0.2gs and this isn't even that much.

That's without using the friction brakes at all

So 0.15g is basically 25% less braking than the amount of braking the car does simply by taking your foot off the accelerator at speed- not touching the actual brake pedal at all

If that was "dangerously hard braking" then regen would cause a ton of accidents, but that's simply not the case.


Stand on the brake pedal and it'll brake around 1.0g so I'm not sure how 0.15 is "hard braking" to anybody who's ever actually used the brake pedal.

You're correct. It's the same as regen braking. But full regen braking is not something I would do as a matter of course. When in traffic (I.e., people behind me) I come off the GO pedal gradually when coming to a light, stop sign, or slower cars in front. When I'm enjoying myself on a curvy road it's full regen and then some. But when I'm on the highway with no one in front of me in my lane, I never go to full regen suddenly for no reason at all. And when I'm behind someone, and there is a clear road ahead of them, I never expect them to suddenly brake by any amount. I don't think other people expect me to brake suddenly either, for no apparent reason. Random braking is probably why 2/3 of all accidents involving electric vehicles are rear end collisions (where the EV gets rear-ended). True, it would be the other guy's fault if he rear ended me and his insurance would pay for damages...but I don't want damages regardless of who's at fault. It would take Tesla weeks to fix it.

I respect your opinion that phantom braking is, what, to be expected? But I don't want it and I want Tesla to fix it.

Oh, and I'm probably one of a growing number of drivers whose actual use of a brake pedal is decreasing.

 

[vikefan]

I've yet to have my car brake hard with NO reason visible, even if it's not immediately obvious at a glance- and I do like 90% of my driving with TACC/AP on.

Oh, I’ll be happy to record the exact spot where phantom braking *always* occurs for me every single time. 100%. It’s a freeway interchange that doglegs to the left and under a bridge. I know the precise moment where the car will slam on its brakes it’s so reliable. I’ve driven over it numerous times now just to prove to myself that it will always do it.

 

[MineIsLadyLu]

View attachment 418730

When I try to describe phantom braking I get a little frustrated with myself in not being able to find the words to describe just what it is that I feel when the car suddenly decelerates for no apparent reason. The graph above shows just what happens (TACC on, Autopilot off). The data was generated via the Accelerometer app on my phone. At the 6-second mark it panicked. A car or two ahead of me, yes, but not in my lane. Everyone was just rolling right along.

0.15 Gs will topple a bag of groceries in the back seat; it will tilt your head forward with a couple pounds of force; it will create a loud noise in your ear from the passenger; and after hundreds of these it is starting to get mighty annoying. OK, hundreds is an exaggeration since I've only had the M3 for about a month now, but I get 1 or more of these every time I go somewhere. It's not just this phantom braking that annoys me. It's all the abrupt little corrections the TACC makes before it settles down when a speed change occurs. In fairness it is not always abrupt; sometimes it's as smooth as silk. It reminds me of the sensation you get when running out of gas (ever done that?). This has been around for a long time, and I wonder why it hasn't been given the attention I think it deserves. My $50,000 car isn't supposed to scare the hell out of my passenger every other day.

Mr. Musk, please fix this.

(I would post this on the Tesla forums but they don't post pictures.)

I call it “Squirrel Mode.” Do you think it’s improved at all with any of the recent software updates? Some people have said yes, but the jury is still out with me.

Do you accelerate through it, while keeping adaptive cruise control engaged? If so, then Tesla possibly could track that driver reaction, and possibly could fix the problem.

 

[Wingsy]

Not trying to beat a dead horse (you old enough to have heard that one before?) or anything but here's another example of braking when a car ahead of me exits the highway. It's very similar to my post #28 on page 2. It slowed from 72 to 50 as the car ahead exited and slowed down, as though the software still thought it twas in front of me. It didn't start accelerating until that car was just leaving the field of view of the front camera. (I didn't have a separate camera to show the screen and road ahead like in post 28.)

Now is this kind of slowdown just for me or has anyone else experienced it too?

 

[Phugoid]

Wingsy, thanks for measuring the phantom braking. I've noticed the same thing and have also been annoyed by it. Ignoring the higher likelihood of a tailgater running into you (seems possible, but not very common), it's just plain uncomfortable for me and my passengers. For that reason alone, I think it should be addressed by Tesla since the purpose of TACC/AP is to make driving long distances more pleasant. It used to do that, but now...not so much.