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Comment by bjterry | Hacker News Reader

I was very confused about this video until I watched it with the sound on. The Tesla beeps at the driver clearly before the accident has occurred, but doesn't appear to decelerate until afterwards.

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I disagree. Watch the horizon, e.g. by putting your mouse on it. During the beeping, well before the collision, the horizon moves upward suddenly, indicating that the nose of the Tesla is dipping due to sudden deceleration or braking.

You're right. What's confusing is the speed reading on the dashcam lags by about 2 seconds.

I believe the speed reading on most dashcams is actually from GPS, so it has to wait until the next position measurement to derive the speed from it.

Most automatic systems brake proportionally to danger. On their own (without driver assistance) the goal is usually to bring an accident down to a "safe" speed like 30mph rather than prevent the crash completely.

I guess the point is to strike a balance between trust in the automatic systems and trust in the driver to make the right decisions.

Another way to look at it is that the system is designed to protect you, not the car. Use automatic braking to bring the crash down to something the car can protect you from, the rest is up to you

Right - automatic braking is for saving lives, not saving cars.

After watching the footage several times, it seems to me like the car is breaking either just before or immediately at the point of impact, certainly way faster than a human driver could.

What I'm curious about is whether the autopilot predicted the crash due to the relative speed of the two cars ahead of it, or if it was reacting solely to the change in speed of the car that braked.

If you look through the red hatchback you can clearly see the brake lights of the 4x4 go on (visible from 0:02, though not yet clear), and brake hard to a stop. The hatchback barely seems to react..

I imagine it'd get pretty annoying (and dangerous) if it slammed on the breaks every time two cars got close. It knew what was happening and was ready to break when the accident actually occurred.

That's not what the article says is happening. The Tesla is alerting because the radar sees the (black) car in front of the (red) car in front (of the Tesla) is decelerating, even if the red car isn't, it's alerting because of that. It doesn't "know" they'll be an accident, it just predicts that it will have to slow.

> if it slammed on the breaks every time two cars got close

With some software I'm sure they can determine some unavoidable accidents before they happen.

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