Monday, May 25, 2015

John Nash, Wardrop's principles, and the concept of equilibrium in traffic assignment

Here is an email that I sent to my "Transport Modelling" class today.

Hi class,

You might have heard the news that John Nash has died in a car crash today. I am not sure if anyone of you has taken a course or read a book on "Game Theory". However by now, you all know about Wardrop's principles and the User Equilibrium and System Optimal concepts in traffic assignment. This isn't very different from Nash equilibrium in game theory.

In a non-cooperative game of two or more players, if each player chooses a strategy and no player benefits by changing strategies while the other players stick to their strategies, then this is called Nash equilibrium. See this scene from the movie Beautiful Mind:

Now compare this with Wardrop's UE in which no user will benefit by changing routes and SO in which the entire society benefits, just like the blond girl scene in the bar in the movie.

Anyways, just wanted to share my thoughts and maybe trigger more thinking in you.


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