Heuristics for a real-world mail delivery problem.

We are solving a mail delivery problem by combining exact and heuristic methods. The problem is a tactical routing problem as routes for all postpersons have to be planned in advance for a period of several months. As for many other routing problems, the task is to construct a set of feasible routes serving each customer exactly once at minimum cost. Four different modes (car, moped, bicycle, and walking) are available, but not all customers are accessible by all modes. Thus, the problem is characterized by three interdependent decisions: the clustering of customers into districts, the choice of a mode for each district, and the routing of the postperson through its district. We present a two-phase solution approach that we have implemented and tested on real world instances. Results show that the approach can compete with solutions currently employed and is able to improve them by up to 9.5%.