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August 26, 2008

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Shockwave Traffic Jams

Here’s the setup:

  • You’re one of 20 or so cars driving around in a perfect circle.
  • No seriously, it’s a perfect circle.
  • So your only job is to follow the car in front of you.
  • And keep your speed at around 20 miles per hour.

The result? You guessed it: traffic jams!

Check out the video evidence.

And apparently this experiment corresponds to real-world observation in at least one important way: In both cases, the “shockwave” of slow-down propagates back through cars at around 12 miles per hour. It’s pretty mesmerizing to watch.

Thanks, Mathematical Society of Traffic Flow!

Posted August 26, 2008 at 3:42 | Comments (1) | Permasnark
File under: Briefly Noted


The most interesting thing about these experiments is that there is a critical number of cars. Below the critical number, the flow continues smoothly, but once you cross the critical point (within a window of about 1-2 cars) you get a jam.

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