Phantom Braking

[jay2000]

I am wondering if phantom braking is only a tesla thing or it is common with other manufacturers as well. When it happens on my M3P on Autopilot, it really shocks everyone in the car. Most of the time, I step on the accelerator and that would be silly if the car is really going to hit something.

[off_again]

It would be foolish to say that this is just a Tesla thing. Radar cruise on both my Mercedes and my wifes old Chevrolet Malibu (think Insignia) had ocassions where you would get the 'imminent crash' warning (worse on the Malibu), and both have started the braking process. But it maybe happened once or twice over multi-year periods - so very infrequent. I have heard that others have seen it occur, but very rarely.

Tesla, while on Autopilot / FSD, do suffer this much more frequently though. Plenty of videos on YouTube covering it and while its got better, its still there.

[jjwilde]

The new Toyotas certainly do it. Also keep thinking parked cars are a danger, you can turn it off to an extent in the toyota.

[GT6k]

It is a feature of all adaptive cruise control/aeb systems as there is bound to be some false alarm rate. The types of phantom braking and severity vary depending on the system. The Tesla I had didn't like double decker buses coming the other way on narrow roads and would often brake just as the bus passed, it also got upset at any closing vehicle which crossed the centre line in front such as passing a cyclist. It once tried to decelerate on a motorway due to a crossing 30mph road on a bridge. I test drove a Honda E which was better but still had some false alarms. I currently have a BMW I3 which has a fairly simple optical system so get confused by big shadows across the road. I have never had a car brake hard they just come off the accelerator, its more the startle factor and once you know about it I find its not a surprise and I anticipate most of the false alarms. Its not just EVs, I know someone with a new Mercedes that had a gradually worsening phantom braking problem up to the point that it came to stop and would refuse to move off.

[andy43]

Model S here - yes it's annoying and potentially dangerous but the worst I've experienced was a VW Caddy slamming the brakes on while overtaking a stationary bus - nearly got rear-ended by a van. Terrifying.
I've worked out you can't leave any of these systems to themselves - so I now knock it out of cruise under M-way bridges, past HGVs, that sort of thing.
There is no way on earth these systems will allow full autonomous taxi driving in the UK. Roads just aren't up to it.

[Lim]

It would be interesting to see the stats. It would be good if NCAP etc could test for this, but it must be quite challenging to get the numbers together.

My opinion is of no use, as I got pretty good at anticipating phantom breaking and turning it off, so I'm not really sure if it's getting better or not. I havn't experienced it recently.

My partner's car rarely phantom breaks, but is much less ambitious in scope, so again hard to compare.

[Rozzers]

The only brands I am aware of with regular and multiple issues with this are VAG and Tesla.

All will throw the odd wobbler of course.

[anonymous-user]

Just do an internet search on 'phantom braking'.
See which manufacturer's name populates the top results.
Hmmmmmmmmm........

[Michael_B]

GT6k said:

The Tesla I had didn't like double decker buses coming the other way on narrow roads and would often brake just as the bus passed

This happened to me within a week of owning my Model 3LR, and even though I had read about it, the whole episode was still quite a shock. It also happened when overtaking a lorry plus trailer unit on a French motorway when the driver started veering into my lane. That was more frightening as of course I would have preferred some phantom acceleration instead!

Those are the only two occurrences in 2800kms of ownership. Now I just go briefly into manual mode where necessary or take a slightly wider/narrower line past obstacles and it's not happened again. Yet.

[raspy]

Happens very rarely with adaptive cruise on my current MB or my previous Toyota and if it does, then the braking is not as severe or rapid as when I have driven Teslas on autopilot.

[Maracus]

Had this on my Tesla M3. It's annoying that you can't just have poverty spec cruise control.

I ended up not using it for a few months then tried it again last week up and down the M40, and it worked 100%.

[Blue Oval84]

My Volvo has done a phantom brake two, or maybe three times in the two years that I've owned it, and I could see why it did it each time (moving from L3 to L2 whilst going around a curve, therefore pointing at a car in L1 and the Volvo thought I was driving straight at it)

I borrowed a Tesla M3 for Christmas and it did it three times on the drive home (340 mile trip), and on no occasion could I figure out why, just ambling along in my lane, with nothing in front.

I won't be taking it again, it's just not up to scratch yet, the Volvo system is relaxing and works predictably, the Tesla system had me on edge.

[Maracus]

Blue Oval84 said:

I borrowed a Tesla M3 for Christmas and it did it three times on the drive home (340 mile trip), and on no occasion could I figure out why, just ambling along in my lane, with nothing in front.

More than likely you were going over a bridge or under one. It seems to pick up the speed limit on the road that is being crossed.

[aestetix1]

If phantom braking is bothering you then it might be worth asking the dealer to check that the radar is properly adjusted.

[Castrol for a knave]

My S7 did it to me in the middle of Birmingham - not running cruise but it had collision avoidance set (not by me, must have defaulted when in for a service the week before).

There was nothing that could have triggered it but it slammed on and the girl in the car behind was thankfully on the ball and hit her brakes in time.

[Lim]

I've often wondered if presence of cars behind change the logic at all? My reverse camera has been clogged with mud recently, and no warnings from AP, so perhaps not?

Are there examples of when AP has accelerated to avoid a rear end??

[DrJFoster]

There are two things here. One is collision avoidance which is an emergency braking system and I've had that when it seems parked cars and doesn't know you've seen them and you're still driving straight at them and not braking. That said, its rarely applied the brakes, it just goes a little crazy on the dash with warnings.

Then there's happily driving doing maybe 70mph and the car brakes for no perceptible reason, and it is a known issue at Tesla. Musk himself even admits it because when asked if the latest beta software was going to cure it, he said he hoped so. Drive along the motorway on an overcast day where there are no shadows from bridges and you might get none, drive a couple miles in the wrong conditions like a low sun and shadows across the road and you might get one every couple of miles. It has nothing to do with the calibration of the cameras, but if in doubt you can calibrate them yourself via the option in the car.

[SWoll]

DrJFoster said:

There are two things here. One is collision avoidance which is an emergency braking system and I've had that when it seems parked cars and doesn't know you've seen them and you're still driving straight at them and not braking. That said, its rarely applied the brakes, it just goes a little crazy on the dash with warnings.

Then there's happily driving doing maybe 70mph and the car brakes for no perceptible reason, and it is a known issue at Tesla. Musk himself even admits it because when asked if the latest beta software was going to cure it, he said he hoped so. Drive along the motorway on an overcast day where there are no shadows from bridges and you might get none, drive a couple miles in the wrong conditions like a low sun and shadows across the road and you might get one every couple of miles. It has nothing to do with the calibration of the cameras, but if in doubt you can calibrate them yourself via the option in the car.

This. Not had it occur quite as regularly as every couple of miles but in the right/wrong conditions it's very poor. I also find the AP cruise control in general not great as drives like a nervous learner most of the time and is very jerky in it's inputs.

I'm also annoyed at the change to the screen layout to provide more space for FSD visualisations in the right hand frame by reducing the size of the satnav/entertainment frame that I'm sure the vast majority of owners use far more regularly. This plus the alterations to the colour scheme and move/resize of the speedo feels like a step backwards to me.

[Otispunkmeyer]

Friend of mine sent a BMW X1 back because the thing kept braking randomly on its own. Not on the motorway mind, but when just driving around in an urban setting.

Their solution was to turn off the collision avoidance each time when getting in the car. He wasn't having that.

[Otispunkmeyer]

Lim said:

It would be interesting to see the stats. It would be good if NCAP etc could test for this, but it must be quite challenging to get the numbers together.

My opinion is of no use, as I got pretty good at anticipating phantom breaking and turning it off, so I'm not really sure if it's getting better or not. I havn't experienced it recently.

My partner's car rarely phantom breaks, but is much less ambitious in scope, so again hard to compare.

I think NCAP do do the ADAS testing. They have inflatable cars, bikes and peds that they can send out in front of cars to test the ADAS functions. But I don't believe any of them test for the likelihood of false positive and the tests are always nearly in isolation; flat open ground with just the obstruction.