Traffic shockwaves are cause of traffic jams

I'm sure everyone has experienced this:

You're travelling along at a nice pace on the highway when all of the sudden everything grinds to a halt. You get a couple miles down the road and everything is moving again, but there was no apparent cause of the slow down; no accident; no busy on/off ramp; no construction; nothing that would have caused it.

The theory of "traffic shockwaves" has actually been demonstrated on a test track in Japan.



And it's all attributed to human error. As one researcher comments: "If they had set up an experiment with robots driving in a perfect circle, flow breakdown would not have occurred."