Transport coefficients for the equilibrium of spatial interaction processes

In a neighborhood of the equilibrium solution of a doubly constrained gravity model of spatial interaction, or of a transportation problem, feasible solutions can be linearly approximated with the use of phenomenological (transport) coefficients. Paths to equilibrium can then be projected. Procedures for computing these coefficients-second-order derivatives of the entropy or the energy with respect to attractivity, emissivity, and distance deterrence parameters-are discussed.