Characterizing Braess's paradox for traffic networks

We generalize Braess's (1968) paradoxical example by defining a Braess paradox to occur when the Wardrop equilibrium distribution of traffic flows is not strongly Pareto optimal. We characterize a Braess paradox in terms of the solution to a mathematical program. Examples illustrate unexpected properties of these solutions. We discuss a computational approach to detecting a Braess paradox.