Tragédia dos bens comuns na mobilidade urbana: o caso de Belo Horizonte

Abstract

This work has sought to evaluate the possibility of the tragedy of the commons in urban mobility in the City of Belo Horizonte, Brazil. In short, this tragedy would occur if the increased car use worse the mobility in terms of time spent in traffic. More completely, it is a study assessing whether the rational individual choice of each citizen choosing the most satisfactory mode of transportation for himself or herself, can somehow effect a result worse for all, that is, if all citizens make the decision by the same criterion. A similar phenomenon had formerly been described regarding the sharing of public ground pastures by certain pastoralists, a sharing whose inevitable environmental degradation result falls into the tragedy of the commons predicate. The latter is a special instance of the Prisoner's Dilemma conception, a game described in Theory of Games. According to the analogy or application proposed here, commons is the road network of a city; and the decision to be made by individuals would concern the dilemma of using either car or bus as their mode of transportation. The chart of choices and rewards for this analogy, seen as a case of the Prisoner's Dilemma in urban mobility, can be considered a pioneer in the literature. Incidentally, the literature reviewed hereby, shows that using buses as a form of cooperation which cooperation if feasible could avoid the tragedy cannot take place in a large city, where travelers generally do not know each other. Using the route database of the Research of Origin and Destination of RMBH 2012, and through a methodology that involved the routing of riding courses; and the estimation of road speeds and densities; the adjustment of a macroscopic traffic model allowing the prediction of traveling clocked times in hypothetical traffic situations; it was possible to compare traveling times, to compare the one situation in which all travelers used only the bus and the another situation in which everyone only used car. The time under this second situation was considered infinite, since the downtown density during afternoon rush or peak hour would reach the maximum value possible. Therefore, the final conclusion of the work is that tragedy of common goods is a real possibility in Belo Horizonte. That is, the rational choice to opt for car because it is faster nowadays; if taken by all citizens, can paradoxically lead to an increase in average traveling time. This has been a proposition of the source literature, but it had not yet been demonstrated quantitatively, as was done in the present work. In this way, this work corroborated previous studies warning society about the risks associated with the increasing use of automobiles in large cities.