Traffic Jam II

If you remember, almost a year ago, I wrote a short article about traffic jam. Today, the Michigan State University Mechatronics class demonstrated what I postulated about "Traffic Jam," beautifully. Although the purpose of the demonstration was just for fun and not at all intended to validate my theory about a phenomenology of traffic jam, it is worth to bring up what I have observed from our demonstration today. 

Traffic jam is one of those understudied urban phenomena which I think deserves a full attention from any academic community since the correct mechanism of how traffic jam occurs and how it propagates remains uncertain. People who think that it happens simply because there are more cars than a road can handle are completely wrong since traffic jam can occur independent of the size of traffic flow as we have seen in the video (from the previous article). There are some papers which try to analyze its mechanisms of formation by parameterizing driver response time, cruising speed, curvature of road,... often resulting in overcomplication of system making it more difficult to understand. 

The following video shows up a case of traffic jam formation when the following parameters are controlled to be uniform independent of individual drivers.
1. Response time
2. Acceleration/deceleration
3. Cruising speed



Notice that when the leader bot is briefly stopped manually, the next bot is then forced to stop after approaching the leader to certain distance. When the leader bot is released and let free to roam, it will be able to follow the leader again, but due to the insufficient response time, the third bot approaches to the second bot and is forced to stop afterward. By the time the third bot starts again, the fourth bot stops and this chain reaction goes on and on. Now, if you stop to think about this, this is analogous to a propagation of localized traffic jam in a form of a wave packet. Also, think about this, whenever you were in a traffic jam and when you think you just got out of the mess, you see a road ahead completely free of cars almost always and didn't the very fact that there wasn't really anything that may have caused the traffic in the first place make you wonder why you had to waste so much time for, literally, nothing?


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