Hacker News Reader

Comment by CamperBob2 | Hacker News Reader

Every autonomous braking system has that problem, including the one in my 2020 Macan. They are dangerously-flaky hacks. As of 2025 they are mandated by law.

View on HN

I own another VAG car with automatic emergency braking. If it is actually applying the brakes for you more than in cases where you are clearly about to rear-end someone, you should consider not tailgating as much. The sensor even gives you a warning if you are following too close at highway speeds.

The radar system they use in modern VW and Audi cars is extremely conservative, claiming to not engage the brakes at all above 35 mph, and waiting until the last possible moment to apply the brakes below that window. It's been absurdly accurate for me. Once every few months or so it "warns" outside of a dangerous situation, but they are almost always situations I could have prevented with a gentler approach to driving, for example following closely a truck with a trailer that is slowly turning off the street will erroneously activate the warning because I'm continuing as if it will be out of my way, which is not the safest.

The time it activated in a real danger situation it didn't even apply the brakes, it "primed" them so that my action of pressing the brakes would happen faster.

If it is actually applying the brakes for you more than in cases where you are clearly about to rear-end someone, you should consider not tailgating as much

Thanks, Dad. Clearly I have no idea what I'm doing, or what I'm talking about, so my real-world experience is invalid.

For the benefit of everyone else, phantom braking is a thing that by definition occurs when you're not following anyone. Such as when the car slams on the brakes upon approaching a car that's clearly about to turn right from a nearby parking lot, but who is equally clearly waiting for you to pass before entering the road.

I think I meant to add more weasel words to that like "consider". Let me be more direct. In 20k miles in this vehicle, I have never once encountered the radar based AEB warning, not even activating, in a situation where it wasn't obviously sensing a car that would be in the path of my vehicle. It has not activated for trash, or overhead bridges, or cars in the next lane over, or any of the number of things everyone else says radar can't handle. It has only ever warned me when there is a car in front of me, sometimes a car that is taking extra time to turn off the road, once because of a car in a suicide lane. In those instances it does NOTHING else than play a generic warning tone and put a red warning on the dash, it never activates the brakes, and does not even do the brake "priming" that it claims to do if it thinks an accident is likely. It is EXTREMELY conservative, to the point that I do not consider it a backup.

I shouldn't have been patronizing, I'm just so confused how the same hardware and (possibly) software can produce such different results. Why would the audi version be so much more sensitive?

>Such as when the car slams on the brakes upon approaching a car that's clearly about to turn right from a nearby parking lot, but who is equally clearly waiting for you to pass before entering the road.

Like I've driven past this exact situation hundreds of times with not even a peep from my car.

I did 30,000 miles in a 2019 outback with a significant amount of phantom breaking, more than I've had in my Tesla or e-tron. Anecdotes don't mean much.

> The radar system they use in modern VW and Audi cars is extremely conservative, claiming to not engage the brakes at all above 35 mph, and waiting until the last possible moment to apply the brakes below that window.

I love my 2021 RS 5, but I have to disagree with this. Even in Traffic Jam adaptive mode, many times it will accelerate towards a vehicle _that it detects_, and only brake very late, and hard. On several occasions I've intervened because I wasn't sure if it would. When I've been alone in the car, I've waited later (and seen it brake hard, of its own accord), when I've held off on the brake since I have no passengers to give whiplash.

It will also absolutely emergency brake above 35mph.

It's possible the features introduced in the upmarket trims are to blame. I have all the hardware for things like distance based cruise control and parking assistance and lane keeping, but the previous owner did not buy them so I ONLY have automatic emergency braking. In 20k miles the worst problem I had was it failing self-calibration and just turning itself off for a few months.

Definitely possible - my girlfriend has a 2017 A4 without anything but AEB, basically, so I have no real comparison source.

Someone else on HN commented this the other day. RSymons RSEV did a comparison[0] of the self-park feature of Tesla's compared to three other cars. All cars nailed the spots they tested flawlessly while the Tesla just straight up didn't see most of the spots. When they moved the cars further and further away so that the spot became more obvious it eventually did see the spot but parked over a foot from the curb

Tesla seems to have a lot of software issues when it comes to "smart" features like these. I wouldn't be surprised if they are indeed worse than the competition, but I'd love to see a similar comparison

[0] https://www.youtube.com/watch?v=nsb2XBAIWyA

Apparently not as common as Tesla. You should read about "phantom braking" issues on Tesla , especially after they removed the radar

Yeah, I can't even imagine what it would be like to implement a system like that without radar. Tesla's approach would make a good Most Interesting Man In the World meme. "I don't always tackle the hardest engineering problems in human history, such as self-driving cars. But when I do, I tie one hand behind my back, close one eye, and consume some alcohol or drugs first."

One episode per 3000 miles is too many, and that's about what I was seeing before I disabled the feature.

Are you referring to the "gentle slow down" behavior that Autopilot often does or the "slam on the brakes as hard as you can" behavior of Automatic Emergency Braking? I definitely see the former more than once per 3000 miles but it doesn't bother me. I've never seen the latter.

In my vehicle, the 'gentle slow down' part that's associated with the radar-driven auto cruise control usually works OK. I'm referring to false triggering of AEB in completely-inappropriate circumstances when no obstacle is in the car's path.

If someone has built an AEB system with the degree of immunity from false triggers that's needed to make it a net positive for road safety, I haven't seen any evidence yet. Similar complaints across many different car models are widespread.

On my car, all of these occurred frequently.

It definitely is erratic with the speed, speeding up and slowing down slightly, which is annoying, but not so dangerous.

The dangerous parts are driving home from work, 6 miles, at least two very hard brakes each trip with no cars ahead of me (I only made a few trips like this before disabling it).

Automatic emergency braking (with the loud beeps and red message on the screen) on two lane highways, over crests, a myriad of other circumstances.

Musk's obsession with not relying on radar and using only cameras as sensors is nuts and likely a big reason why competitors systems perform so much better. But it seems Tesla has finally backtracked on this

https://electrek.co/2022/06/08/tesla-files-use-new-radar-con...

The rate for me was approximately 1 emergency brake maneuver per 6 miles of driving. I doubt any of them are as bad as the Tesla system.

Better a false positive (phantom braking) than a false negative (not braking when it should). I imagine they're all tuned with this in mine.

I think the current state of Tesla's self driving is more dangerous in this respect than I am.

Are you kidding me? One of the several times autopilot tried to kill me was when it randomly tried to flat stop on I-80 with a semi driver following me. No way he could have stopped in time if I hadn't disengaged and slammed on the accelerator.

(Absolutely no reason to stop and no weather or afternoon sun for confusion. My best guess is that flaky vision systems thought a semi truck was entering my lane, but I really don't know.)

But it didn't kill you. If you had a false negative, that means it failed to stop when it should have, and that almost definitely would have caused an accident. False negatives are more dangerous than false positives. Both can be dangerous, but false negatives are worse.

All AEB's from all manufacturers have a certain amount of phantom braking, but non-Tesla AEB are well studied and definitely save lives.

GP gave an obvious example of a false positive. I don't why them thinking fast enough to save their life neglects the point...

"Here's a drug that is guaranteed to prevent pancreatic cancer if you take it every day, but is very likely to give you one or more heart attacks at random intervals. Even if that happens, though, you'll probably be OK, because most of the heart attacks won't be all that severe. Want some?"

"Oh, by the way, starting in 2025, your breakfast cereal will be legally required to contain this drug."

Reply on news.ycombinator.com