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Phoenix666 [soylentnews.org] writes:

Drivers are only too familiar with phantom traffic jams [here.com]: those occasions when you slow to a complete standstill, which frustratingly appear to have no concrete cause. In fact, they do have a cause – just not an obvious one. Thanks to decades of scientific research, we now have theories that not only explain why jams happen but point to ways of preventing them.

Experiments on traffic flow date back to 1933 – just 25 years after Ford’s Model T went on sale. American traffic engineer Bruce Greenshields took a movie camera out to a section of highway to record how many cars passed along it, and how long it took them.
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For traffic, it was mathematicians James Lighthill and Gerald Whitham who came up with a theory to predict the properties of a highway. Inspired by “theories of the flow about supersonic projectiles and of flood movement in rivers”, it used the physics of kinematic waves, treating traffic like particles in a liquid.

The theory introduced the idea of shock waves in traffic. In places where cars slow up or accelerate, a traffic wave ripples back down the road. Waves, they said, were “likely to occur on any stretch of road where the traffic is denser in front and less dense behind.”
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In other words, traffic jams needn’t be caused by a broken down vehicle or an accident. Just as, under the right conditions, a speck of dust can cause water vapor to condense into liquid in a cloud, the actions of a single driver could cause a jam.

MIT traffic researcher Prof Berthold Horn explains: “Suppose that you introduce a perturbation by just braking really hard for a moment, then that will propagate upstream and increase in amplitude as it goes away from you. It’s kind of a chaotic system. It has positive feedback, and some little perturbation can get it going.”

Horn has developed an algorithm that could smooth out traffic jams, technology permitting. If cars could sense the distance to other cars both ahead and behind them, they could keep an even distance between the two. A simulation shows the algorithm taking effect after the traffic first bunches up:

Interesting article worth reading in full, complete with illustrative animations.

Original Submission