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MIT mathematicians model traffic jams like detonation waves

Most drivers have been stuck in a traffic jam at one point or another. Some of the jams are caused by an accident or closed lanes. Other traffic jams crop up with seemingly no reason.

A group of mathematicians at MIT is working on the development of a new model to explain how and why these so-call phantom traffic jams form. According to the researchers, these types of phantom traffic jams form when there are a lot of cars on the road and small disturbances like a driver hitting the brakes too hard or getting too close to another car. These little disturbances can escalate into a self-sustaining traffic jam.

The model developed by the team of researchers may help road designers build roads to minimize the possibility of phantom traffic jams. The key to the study is the discovery that the mathematics of these jams called jamitons are very similar to the equations used to describe the detonation waves produced by explosions.

The discovery of the jamitons allowed the researchers to solve traffic jam equations first theorized in the 1950's. The equations are reportedly similar to those used in fluid mechanics and model traffic jams as self-sustaining waves. The equations allowed the researchers to calculate the conditions that case a jamitons to form and how fast the jamiton will spread.

According to the researchers, once this type of jamiton forms it is nearly impossible to break up and a driver’s only choice is to wait the jamiton out. The researchers say that the new model can help road designers to determine speed limits that are safer and find stretches of road where accidents are more likely.

One of the researchers, Aslan Kasimov, said, "We wanted to describe this using a mathematical model similar to that of fluid flow." Kasimov and his team say that they discovered that jamitons have a sonic point that separates traffic flow into upstream and downstream components. Communication of the cause of the jamiton to drivers it the downstream segment of traffic is impossible say the researchers.

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RE: humans
By mmcdonalataocdotgov on 6/10/2009 11:40:18 AM , Rating: 2
True to that. It is not speed, but variations in speed that cause density waves. The people who go slow force other people to go around them, which forces people in the other lanes to slow and try to go around further, which forces etc. Density wave.

RE: humans
By radializer on 6/10/2009 8:03:46 PM , Rating: 2
On those lines, when I was living in the Phoenix metro area, I was once pleasantly surprised when the speed limits of a certain stretch of the Loop 202 freeway increased (yes increased! ) from 55pmh to 65pmh.

As for the reasons behind this ... everyone used to drive that stretch of freeway at speeds of 70mph, and rumor has it that those who actually stuck to the 55pmh speed limit were causing a traffic hazard - so I guess ADOT (or whoever sets these limits) figured they'd up the limit to 65mph to improve traffic flow.

By the way, if you drive out on I-10 headed east from Tucson towards El Paso ... the posted Minimum Speed Limit is 65mph almost through all of New Mexico.

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