Incentivizing efficient use of shared infrastructure: Optimal tolls in congestion games
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Throughout modern society, human users interact with large-scale engineered systems, e.g., road-traffic networks, electric power grids, wireless communication networks. As the performance of such systems greatly depends on the decisions made by the individual users - often leading to undesirable system behaviour - a natural question arises: How can we design incentives to promote efficient use of the existing infrastructure? Here, we answer this question in relation to the well-studied class of congestion games, used to model a variety of problems arising in theory and practice including traffic routing. In this context, a methodology for designing efficient mechanisms is so far missing, in spite of the vast scientific interest. In this manuscript, we resolve this problem by means of an elegant and computationally tractable approach, recovering and generalizing many results in the literature. Surprisingly, optimal mechanisms designed using local information perform closely to those designed using global information. Additionally, we show how mechanisms that perform optimally in the continuous-flow approximation (marginal cost tolls), worsen the performance when applied to the original discrete setup.
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