  Consider a distribution of citizens in an urban area in which some services
(supermarkets, post offices...) are present. Each citizen, in order to use a
service, spends an amount of time which is due both to the travel time to the
service and to the queue time waiting in the service. The choice of the service
to be used is made by every citizen in order to be served more quickly. Two
types of problems can be considered: a global optimization of the total time
spent by the citizens of the whole city (we define a global optimum and we
study it with techniques from optimal mass transportation) and an individual
optimization, in which each citizen chooses the service trying to minimize just
his own time expense (we define the concept of equilibrium and we study it with
techniques from game theory). In this framework we are also able to exhibit two
time-dependent strategies (based on the notions of prudence and memory
respectively) which converge to the equilibrium.
