Professor Jean Philippe Vial, University of Geneva, present this lecture on; “Traffic Equilibria with Elastic Demands”
Abstract:The solution of the traffic assignment problem with elastic demand is an extension of the standard Wadrop equilibrium for problems with constant demands. Under general conditions, the equilibrium can be computed as the solution of an optimization problem, whose objective is the sum of a congestion function and a disutility function. The problem with elastic demand is well-documented in the literature, but the reported numerical analyses deal with small problem instances only. In our study, we use Lagrangian relaxation. It leads to a concave dual problem with a two component objective: a nondifferentiable one and a smooth one. We exploit this special structure in connection with the Analytic Center Cutting Plane Method (ACCPM). We report results on classical transportation problem instances (Barcelona, Winnipeg, Chicago-region); some of them are very large.
Biography: Jean-Philippe Vial has been professor of Operations Research and Logistics since 1970, firstly at CORE (Center of Operations Research and Econometrics, Catholic University of Louvain, Belgium), then at the University of Geneva. He paid long term visits to the University of California, Berkeley, and the University Louis Pasteur, Strasbourg, France, and many shorter visits to University Paris-Dauphine (France), Institut d’Economie Industrielle (Toulouse, France), Technion (Haifa), Technical University of Delft (The Netherlands), GERAD (Montreal, Canada), INRIA (Grenoble, France). He his now Emeritus, but he pursues his activities in the consulting company ORDECSYS (http://www.ordecsys.com ) he co-founded with Professor A. Haurie.
Jean-Philippe Vial is a specialist is Logistics, Operations Research and Algorithmic. He has been very active in developing new techniques for solving large-scale optimization problems, such as those arising in multi-regional planning and in the dealing of uncertainty. He has contributed new numerical methods for optimization and has developed specialized software in this area. He has strong interest in applications of logistics, in particular in the area of environmental management. The algorithmic tools he developed are instrumental in the coupling of regional models. The same tools make it possible to couple physical models (climatic change, gas diffusion) with economic models. He chaired the Mathematical Programming Society for three years, and has particpated to the jurys of some prestigious international scientific prize (Tucker prize, Franqui prize). He has delivered several plenary or semi-plenary invited talks at international conferences.
Chair: Professor John Pollak, Centre for Transport Studies
Afternoon Tea and Coffee will be served in CPSE Common Room, Top Floor Roderic Hill Building at the end of the seminar.