A Variable Neighborhood Search Approach for Solving the Car Sequencing Problem∗

In this paper we present a new method for solving large instances of the Car Sequencing Problem (CarSP) including constraints defined by the assembly shop and the paint shop. Especially the latter are of greater significance, since they allow no violations. Our approach combines general Variable Neighborhood Search with Integer Linear Programming (ILP) methods and benefits from the advantages of both techniques. While two neighborhoods—Swapping and Inserting—are adopted from previous work, two others are based on a new ILP formulation for CarSP, and CPLEX is used as general purpose ILP solver for identifying best solutions within these neighborhoods. The comparison with results obtained during the ROADEF Challenge 2005 shows that this approach is promising and competitive. In particular, we were able to obtain some new, so far unknown best solutions for some of the ROADEF instances.