Excerpt from On the Performance of User Equilibria in Traffic Networks
While Wardrop (1952) had introduced the concept of Nash equilibrium to describe user behav ior in traffic networks, traffic engineers have proposed to utilize user equilibria in route-guidance systems to prescribe user behavior. Yet, Nash equilibria in general and user equilibria in particular are known to be inefficient (dubey and critics favored in principle the difficult-to-implement system optimum, which guarantees that the average travel time is minimal. Hence, the recent result that user equilibria are near optimal (roughgarden and Tardos 2002) came as a welcome surprise, which may help to justify the use of user equilibria in retrospect.