[kabes]

A lot of traffic jams are so called shockwave/phantom traffic jams and a lot of other ones are where lanes have to merge in each other. Those could be avoided with self driving cars. Maybe in the beginning they will be too cautious for that, but after some time and experience, I'm sure these optimizations will be implemented.

It may not make the traffic in downtown SF faster, but it sure will make the traffic on the 101 from SF to San Jose faster. And good luck walking that.

[dragonwriter]

> A lot of traffic jams are so called shockwave/phantom traffic jams and a lot of other ones are where lanes have to merge in each other.

And, to build on this point, a lot of urban ones are produced or exacerbated by improper behavior at stoplights.

[erispoe]

It is true but as pointed the benefits are mainly on highways.

[saosebastiao]

Those won't go away. They might be mitigated, but once again, you can only mitigate the portion that is due to driver error, and the major problem in those scenarios is physics.

The shock wave phenomenon is one caused by physics (it literally is modeled by fluid dynamics simulation), exacerbated by limited visibility, and exacerbated once again by human reaction times. You can only get rid of the human reaction times, and maybe a little bit of visibility due to communication (although I'm extremely skeptical that there is any incentive for cars to rely on wireless communication to make decisions).

Lanes merging is a physical bottleneck. Sure, humans might make the merge worse, but speed is still limited by the capacity bottleneck, not the friction of the merge. The zipper merge has never proven to be faster, merely safer and more space efficient. You'll get to the bottleneck faster, and cars that try to exit before the bottleneck will get out of your way faster, but that's about it.

[jedberg]

Those traffic waves are in large part psychology though. If every car traveled at the average speed you wouldn't have them. If even just 10% are self driving and have data on average speed for that section of road, they can not only avoid the wave but break them up, making traffic better for everyone.

I've even done this myself. I see a standing wave in front of me and slow to what I know is about average for that time of time. People cut in front of me as the gap gets bigger, but by the time I get to the choke point the wave dissolves as I pass through, and everyone behind me who was pissed about my slow speed is suddenly happy.

[saosebastiao]

I'm not convinced, and I don't think there is very much evidence either way. Are the traffic waves caused by erratic driving due to driver error at misjudging average speed? Or is it more caused by small fluctuations due to actual and unavoidable conditions? Would a self driving car see a plastic bag blowing in the wind and slam on its brakes, or drive right through it? What about a kitten? What about a bowling ball, or an unsecured 2x4 falling off a truck? Any one of those situations can cause a shock wave.

We know, due to fluid dynamics simulation, that reduced reaction times will make traffic more resilient to small fluctuations in speed (they can "recover" from the shock wave with lower space requirements), but when the freeway is at capacity there is no recovery room and the shock wave will happen regardless of reaction time.

[bashinator]

I try to leave 10-20 car lengths between myself and the next vehicle in this kind of stop-and-go heavy traffic. No waves for me! The anti-traffic essays indicate that doing what I'm doing will actually speed up the breakup of a traffic jam.

[galdosdi]

That's true, but depending on the local driving culture, this may just lead to many vehicles cutting in front of you and making the gap vanish. In metro NY/NJ, at stop-and-go speeds on freeways, 1 to 2 car lengths seems to be about as much as you can safely leave without it quickly being snatched away. Too bad.

[bashinator]

Cars cutting you does not make the gap vanish - you just have to slow down marginally more for a short amount of time.

[crucini]

This is an interesting insight. What if we replace 20 sequential cars with a huge "road train" ala Australia - a tractor with multiple trailers?

The road train has no cushion (ignore the few inches in pintle hooks) so it brakes as a unit. And accelerates as a unit. Does that make it's recovery from shocks 20x as good as 20 cars?