Mail-Delivery Problems with Park-and-Loop Tours: a Heuristic Approach

We are solving a tactical mail delivery problem by combining exact and heuristic methods. Routes for postpersons have to be planned visiting 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. In addition, it is possible to change the mode in the tour and walk a loop, which is called parkand-loop. Thus, the problem is characterized by several interdependent decisions: the clustering of customers into districts, the choice of a mode for each district, the routing of each postperson through its district and the starting points for park-and-loop subtours. We present a two-phase solution approach that we have implemented and tested on seven real world instances. Results show that embedding park-and-loop subtours achieves significantly better results compared to single mode routes. Keywords— mail delivery, park-and-loop, set covering, heuristic;