Column generation for multi-matrix blocking problems

The blocking problem in railroad freight traffic is a tactical routing problem. The problem was modeled as an arc-based MIP in former publications. We reformulate the problem and introduce a new model. The modified objective function can be handled easier without loss of structural information. Nevertheless, real instances cannot be solved by standard algorithms. Therefore, we present a column generation approach. The model is reformulated in a path-based way. We exploit the new model structure in the pricing step. Sets of new paths for each relation are generated in polynomial time.