text: how can i model traffic jam ?   not sure exactly what you mean by "model."  if you are good with math and are looking for a computer model, i would try out a program called "extend 5lt."    this program is used by manufacturers, industrial engineers and others who need to simulate stuff.  it is a little difficult to learn in the beginning but it is a very valuable tool.  i believe they still have a free version available at the web site below.  good luck.