Solving symmetric vehicle routing problems asymmetrically

The vehicle routing problem can be regarded as a traveling salesman problem with additional constraints. Algorithms based on assignment relaxations provide better solutions for the symmetric traveling salesman problem if they are used on an asymmetric transformed distance matrix, as shown by Jonker et al., in a paper in Operations Research. The generalization of such a transformation to the distance matrix of symmetric vehicle routing problems is described. The approach is illustrated within a heuristic algorithm, although it can also be the basis for an exact algorithm. For a number of standard problems computational results are given, that are competitive to results of other algorithms.