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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: Why do they happen?
By mmcdonalataocdotgov on 6/10/2009 11:33:47 AM , Rating: 2
These traffic jamitons, long called "brake checks" to truckers, are more like the density waves that form when there is a slower particle in the fluid.

The real culprits are LONG on ramps since people stuck back in the jam jump the white line to the right and get on the on ramp and perpetuate the problem. A long on ramp with foils to prevent on ramp jumpers would be more beneficial.

Another cause I notice is that traffic will move along pretty well when the road twists and turns, or has been straight for awhile, but as soon as the twists stop, the lane that is on the inside of the last turn stops. It is because people look up the lane they can now see for a long distance, count all the cars (regardless of speed) and think there are too many people in the lane and they brake. I call this the telephoto effect. They think since there are a lot of people ahead (that they can now see but couldn't when they were in the twisties) they stop. Watch this yourself. Whenever a twist in the road goes on to a straight, if the last twist is to the left, the left lane stops. If the last twist is to the right, the right lane stops. I'll bet lunch on it. But it is a visual effect, not a density effect.


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