TACTICAL DESIGN OF RAIL FREIGHT NETWORKS .2. LOCAL SEARCH METHODS WITH STATISTICAL-ANALYSIS

This paper deals with the statistical study of the local search method s which we used in Part I of this work. In that part, a tactical plann ing model of the rail freight transportation was defined as a network design model. Different local search methods have been used to solve i t: Simulated Annealing, Tabu Search and a 'Descent' method, The soluti on and method convergence depends on the initial feasible solution and the convexity of the feasible region, so the comparison among them wi ll be made with the help of statistical theory. Assuming the hypothesi s that the distribution of local minima can be represented by the Weib ull distribution, it is possible to obtain an approach to the global m inimum and a confidence interval of this. The global minimum estimatio n has been used to compare the heuristic methods and the parameters fo r a given heuristic, and to obtain a stopping criterion.