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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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Why do they happen?
By mdogs444 on 6/10/2009 11:23:08 AM , Rating: 2
I've often wondered how traffic can come to a full stop when there are no stop signs or streetlights and no cross roads to turn off onto.

The biggest reason is too many cars getting on and off the exits close to the same time. The exit ramps are notoriously too short, and the entrance ramps usually merge onto traffic way too soon.

I wish they'd create a wall for a half mile before the exit so people cannot merge at the last second, and a wall at the entrance for at least half mile that splits into two lanes before it can merge with traffic. This won't solve all the problems, but i'm sure it would help.

Some might say its a danger putting a wall there because someone might hit it...but if they hit the wall at the merge/split...then its one less driver we have causing traffic jams! :)




RE: Why do they happen?
By FITCamaro on 6/10/09, Rating: 0
RE: Why do they happen?
By mdogs444 on 6/10/2009 11:28:38 AM , Rating: 2
Yup - we all win in that case. Less cars on the road, population reduction by survival of the fittest, less emissions, less gasoline consumption...and I can get where I'm going faster.


RE: Why do they happen?
By inighthawki on 6/10/2009 11:33:43 AM , Rating: 5
What happens is that a car will step on a brake, and any good driver behind them, especially on the freeway, wants to make sure they also slow down to a point less than or equal to the speed of the car in front. More often than not it will be less then, in which case the cars behind that car also brake, and we have something of a chaos effect going here. A small step on the brake can eventually lad to a huge traffic jam.


RE: Why do they happen?
By arazok on 6/10/2009 1:52:16 PM , Rating: 2
I read a study a while ago regarding the impact of adaptive cruise control on traffic congestion, and the authors determined that if only 20% of cars utilized it, then traffic congestions would be cut in half.

These are cruise control systems that will slowdown automatically if another car is in the way, then accelerate again when if moves.

It’s funny how governments focus on MPG, biofuels, and expensive hybrid technology as a solution for our environmental problems – but if they simply mandated an existing and (somewhat) cheap technology be installed in every car we could reap benefits far in excess of these solutions.


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.


RE: Why do they happen?
By bhieb on 6/10/2009 11:40:03 AM , Rating: 2
That would only push the jam further up stream. They will still wait until the last minute to get over inside the wall, thus creating a slow down further back. Problem is just too many cars not enough road. By the time a construction project finishes that was meant to "fix" the problem the number of cars have outgrown the fix, and construction has to start over. The fixes are 10 year ordeals.


RE: Why do they happen?
By nixoofta on 6/10/2009 2:33:14 PM , Rating: 4
quote:
The fixes are 10 year ordeals.


Often referred to as "Godd4mmitons"

Okay, okay, I'll stopiton already...:P
(In my own defense, I laughiton-ed so hard at "jamitons". I don't know how someone could say that with a straight face....iton.)


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