The Guest List: Solving the Mystery of Traffic Jams

Have you ever been stuck in traffic for hours, only to come out at the end of the traffic jam to see no apparent reason for the cars to have stopped in the first place? Driving back from Nashville after Thanksgiving last year, this happened to me twice on a particularly long and rainy stretch through the mountains near Asheville. I was glad to see that nobody was hurt, but wondered how I could have been in crawling, stopped traffic for over an hour without any apparent cause.

Soon afterwards, I saw that Science Daily announced that a team of mathematicians have developed a model that explains why this happens:

"Their model revealed that slowing down below a critical speed when reacting to such an event, a driver would force the car behind to slow down further and the next car back to reduce its speed further still. The result of this is that several miles back, cars would finally grind to a halt, with drivers oblivious to the reason for their delay."

So, the lesson for drivers seems to be one that is common-sense (yet always seems to bear repetition) - stay alert and react quickly but appropriately to the traffic around you.

One way to demonstrate this concept at home is to take out a sleeve of plastic cups and a stopwatch and sit at the kitchen table. Have everyone sit around the table, except for one person who runs the stopwatch. Mark one of the cups to identify it as the "lead car" and time how long it takes to pass it around the table. Then add additional cups, with a 1-minute penalty if any of the cups touch each other as they are passed around the table. It will take longer each time for the lead cup to get from start to finish. This should be a good demonstration of the ripple effect of adding variables (traffic).

It's interesting to see how some complex scientific and mathematic theories (such as chaos theory, in this case) affect our everyday lives!