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Comment by toast0 | Hacker News Reader

Automatic emergency braking systems don't generally brake for stationary objects once the vehicle is going beyond parking speeds. They're really designed to reduce colission forces between vehicles in motion (or recently in motion), and some more recent systems try to reduce forces between vehicles and pedestrians.

A Tesla is happy to slam into a parked emergency vehicle at full speed, as has been demonstrated several times; it's not surprising they don't stop for trees either.

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A Tesla will, yes. But even a small Toyota Yaris will absolutely smash the breaks if you try to drive above parking speeds against something. It's EuroNCAP mandatory for top rating so every 5 star rated car from 2021 has this.

Teslas are 5 star rated, so how does that work?

An F150 will too. Are we sure a Tesla won't?

My 2018 Subaru Forester will absolutely emergency autobrake at highway speeds. I've seen it happen when it detects a car exiting out of the lane as still being in the lane (road is curved so car is still in front, but I have no intention of following it).

> I've seen it happen when it detects a car exiting out of the lane as still being in the lane

The car it braked for was also in motion, or recently in motion, right?

Hmm, true, perhaps that was a bad example. It also brakes for cars that are waiting to turn (completely stationary) that it thinks I'm approaching too fast (say at 40 mph).

Not true for Subaru, mine emergency brakes with objects ahead at any speed

So it will emergency break on the highway if something flies in front of the car? Sounds dangerous and unlikely.

It is possible to see a difference between a fly, bird or car..

Right. I somehow doubt Subaru is ahead of the game compared to Tesla on that.

I took a look at how Subaru Eyesight works. It uses a dual camera system to identify a vehicle ahead and apply braking if it slows down, pedestrians and other specific patterns. Some of it is limited to a 19mph closing difference (surprise).

So the statement above that “mine emergency brakes with objects ahead at any speed” is, unsurprisingly, incorrect.

It doesn’t react to any object and would probably happily hit a tree under the right conditions, or a parked car. Happy to be proven wrong with a demonstration video of the car at full speed.

Uhh, no, it's totally correct that it will slam on the brakes.

Source: own a Subaru, have driven it at a cardboard box in the middle of the street, and have had it slam on the brakes. Have also had it slam on the brakes when swerved into my lane, saving me from an accident. So... worth it.

A Tesla Will also slam on the brakes in general. Swerving into your lane likely fits the 20mph window that Subaru is designed for. But that’s not what’s in question in this comment thread.

Have you tested yours again a stationary emergency vehicle or a tree? Otherwise there isn’t much to discuss here.

Did you read what I wrote? I drove it down the street at a cardboard box and it slammed on the brakes and stopped.

Tell that to my Lexus, which 100% does beep and will smash the automatic brakes if I try to drive into a stationary car behind me.

Are you doing that at parking speed or highway speed? The rules are different.

This is not true for Teslas, and I've tested it (in a safe environment) in my own. It uses vision, as well as radar, to detect obstacles, and will brake from highway speeds to zero when there is a car stopped ahead.

I don't think it's guaranteed though. I've noticed the same as you, but I've also had it lock the brakes after seeing a shadow (lol) and I've had it speed up to 70 mph on Topanga Canyon Blvd (speed limit 45 mph) and nearly run into a parked semi.

This varies based on exact hardware revision, software revision including OTA updates, and active settings at the time. I don’t think anyone but Tesla can make any definitive statement about the behaviour of any given car at any given point in time.

That's insane! That alone should make it illegal on the road.

I agree and I can't fathom why this is an unpopular opinion. It's bad enough when my phone or computer suddenly works differently (or not at all!) due to mandatory OTA update. It'd be terrifying if it my car's safety features could do the same.

Except the kind of radar used in a Tesla cannot do that for you hence while the AP ignores static objects and crashes happily into parked cars, fire trucks, ...

Here's an explanation of why written on here a long time ago by @chowells: https://news.ycombinator.com/item?id=16239612

This user wrote:

To add even more detail, as there still appears to be a lot of confusion:

The radar systems in these vehicles send out a radio pulse in a broad approximate-cone forward. They get bounces back from everything that reflects radio in front of them. Distance from the object is calculated by time between pulse and response. Speed towards/away from the object is calculated from Doppler shift of the radio frequency.

There are two main things that these systems can't detect.

1. Speed of the object perpendicular to the direction of radio wave travel.

2. Location of the object within the approximate-cone the radio pulse travels in.

Note that thanks to the second, you can't calculate the first with higher-level object tracking, either.

So the data you get back is a list of (same-direction velocity component, distance) pairs. There's no way to distinguish between stationary objects in the road and stationary objects above the road, to the side of the road, or even the surface of the road itself.

Radar just doesn't provide the directional information necessary to handle obstacle detection safely.

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