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Comment by a_cardboard_box | Hacker News Reader

In this case the Tesla slammed on the brakes and changed lanes, so there wasn't a realistic way for the other car to prevent the collision.

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You're right. The first rear-ending may have been unavoidable. However, you can see from the rear surveillance camera that subsequent vehicles could have stopped if everyone agreed to keep larger following distances. As mentioned elsewhere in the thread, there is the game-theoretical issue of other drivers cutting in when large gaps form so it would take some coordination on a technology / policy / cultural level to resolve the issue.

The Tesla changed lanes and instantly became a stopped object. The car that hit it did the same, and so did every subsequent car. The follow distance to avoid a collision at that point is about 10 car lengths, or roughly the average stopping distance.

That's just not true. The two cars behind that one were well more than two car lengths apart. Following too close is a non-sequitur.

Unless they are going under 13mph, two car lengths is too close.

I have always heard you should keep two seconds between cars. So at 20mph, you are 60 feet apart. At 60mph you are 180 feet apart.

In any case they stopped successfully, it was the ones behind them that pushed them forward.

> drivers cutting in when large gaps form

if they do, so what? even if 10 people cut in front of you, with a 30 minute drive, how much time are you really losing? 50 seconds?

Curiously the vehicle behind the Tesla barely hit it whereas the drivers of the cars further back in the pileup seemed to have paid less attention.

There would have been multiple ways for the cars further back to prevent a pileup: Drive slower, keep more distance. If you speed, have both hands on the wheel, look at the road, and be ready to brake quickly.

It does sound like there were no severe injuries, so you could argue that people kept enough distance to avoid serious injuries.

There are lighting conditions that could play a role here since this was when people were entering the tunnel. This might also be something that freaked out the Tesla. But it is hard to know without being in the situation.

Even if all the vehicles following each had the same following distance and reaction time, each of them is going to encounter a vehicle stopping more quickly than the one in front of them did. So even if everyone performs similarly, the cars at the back are going to hit harder.

It’s really hard to tell, but to me it looks like the one behind that one managed to stop in time. But only with the tiniest margin. Action further back was much more dramatic, that’s for sure.

The Tesla looks like it slowed down 200+ feet over 4 seconds. That's far from slamming on the brakes. It's also, however, very far from expected behavior which could explain why the drivers behind didn't slow down enough in time. They weren't expecting the Tesla to come to a complete stop. I'd guess if the other car was a Tesla it probably would have stopped in time to prevent the collision because it's basing its decisions on the environment not based on prior experience driving in that particular spot.

I'd also argue that the Tesla pulling over into the left lane (merge 1 lane left vs 3 lanes to the right) is the right behavior in a situation that warrants stopping. Try to get to the side of the road so other cars can pass.

that is, in fact, slamming on the brakes. your estimate of 200+ft over 4 seconds, assuming perhaps a low highway speed of 60mph, is faster than many cars are capable of stopping, even assuming zero reaction time.

It's ok, the car may have cut people off and caused an accident, but if you look at it on the basis of the the number of fatalities/mile, cutting off and causing a minor accident is no big deal. Clearly keeping Tesla's stock price up is a bigger deal.

It's cars 3,4,5 or 4,5,6 that really hit hard.

Coming to a full stop in the left lane is really last-resort stuff. That is the speed/passing lane (in most jurisdictions, all lands are speed/passing around the Bay Area and especially on the bridges).

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