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Comment by zaroth | Hacker News Reader

His car increased speed because the adaptive cruise was set to a higher speed than his car was going, and for 4 seconds before impact there were no cars in front of him.

The adaptive cruise increased speed to his set point when his car left the flow of traffic. The AEB will not trigger on a stationary object at highway speeds. I do not believe there exists any AEB that will emergency brake at highway speed, maybe except perhaps for a pedestrian shaped object?

He hit a crash attenuator which had not been reset (so basically direct impact with concrete) after it had been hit by another car 11 days prior.

Resetting the attenuators is a simple task, but apparently this particular one is hit fairly frequently.

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I don't understand that the attenuator wasn't reset. In my country the lane will stay closed until all safety feature are operational again, including replacing the guardrail.

Yea so in America, transportation departments are either underfunded, overworked and other times delayed due to contracting laws. So instead of some guy coming out to replace the attenuator, they need to by law put out a contract to hire some guy and go through a months long process to approve it. If they don't, some random guy might sue them for not putting it out to bid, etc, etc. It's just never ending stupid.

Where I live, there's a guardrail that is so heavily bent out of shape from constant crashes that it needs some serious replacement because it'll eventually give and allow cars to fly into the opposite lanes. The problem is there was already a contract to replace 10 miles of guardrail issued a year ago and the contractor has not reached this part of the road yet. The DoT can't just go replace it themselves early.

>crash attenuator

>this particular one is hit fairly frequently.

Interesting way to build your road infrastructure

With the number of people who drive drunk or sleepy or while texting, crashes are inevitable.

Unfortunately tesla autopilot drives like an impaired human.

Not a big fan of bay area roads, but this particular junction sees crashes because of a high frequency of law breakers. There is only so much you can do against a large number of people that are super-happy to break the law because the fine/insurance rate is probably not a big deal.

One way or another highways have portions where there has to be a solid, flat, vertical surface on the edges of barriers, exit ramps, etc. It's similar in many ways to the hairy ball theorem.

https://en.wikipedia.org/wiki/Hairy_ball_theorem

You can't just round over the edge of the barrier, because that still leaves a portion where a car could collide perpendicular to it. You can't just slope it down to the ground, unless you want an impromptu Dukes of Hazzard reenactment. You can't have just an unguarded edge because that would just be a death sentence if you hit it at any appreciable speed. The solution is to place those crash attenuators so that it slows the vehicle down over a small distance rather than just over the length of the crush portion of the car.

https://megarentalsinc.com/sites/default/files/feature-image...

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