Size limited iterative method (SLIM) for train unit scheduling

In this work, we are developing a hybrid method driving a core ILP solver with an iterative heuristic for the train unit scheduling optimization problem, which is formulated as an integer multi-commodity flow problem. This approach aims at reducing the problem to a minimal size but still retaining all the essential components for an optimal solution. This research is focussed on two aspects, (i) creation of an initial feasible solution, (ii) iterative improvement on a minimal sized problem extracted from incumbent best solution(s).