Traffic micro simulation - a simulation of how traffic flows in different road scenarios, including the phantom traffic jam.

Traffic Microsimulation

Many times across my site you'll come across mention of driving practices and how small changes you make will affect the entire traffic flow. It's the so-called Butterfly Effect but it applies equally well to a flowing system in motion such as traffic. Ever been stuck in a traffic jam and when the traffic started moving again you wondered WTF? There was no crash, no lane closure - no reason at all for the traffic to have slowed down. That's what is called a Phantom or Shockwave traffic jam. Cars slow down just enough that miles behind them the traffic eventually comes to a complete stop.
Martin Treiber at has done a lot of research into traffic flow and has written this simulation which shows the effect very clearly. He has kindly allowed me to reproduce the java app here for you to enjoy.

How to use this app

It's all pretty self explanatory with the various buttons and sliders. If you want to see the phantom traffic jam, just select option 1 - ring road - and let it run. With no interaction from you, you'll see the shockwave effect for no reason. Fiddle with the sliders to change the traffic flow, number of trucks etc and eventually you'll reach an equilibrium where the traffic flows smoothly.
Messing with the sliders on the on-ramp option will show you how a few idiots who can't be patient or don't understand the concept of "give way" or "yield" can make an entire motorway clog up for no good reason. The same goes for the lane closed option. Anyway - spend some time with the app and have fun. Hopefully it will help you better understand how traffic flow works. If you're interested in the research and background behind this app, Martin has all the information available in papers on his website. (

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