Real-time management of vehicle breakdowns in urban freight distribution

This paper considers a problem in which an unexpected event immobilises a vehicle of a distribution fleet permanently, and the remaining vehicles are rerouted to serve some of the clients of the failed vehicle. We model this case as a variation of the Team Orienteering Problem (TOP), constraining all vehicle routes to an upper time, or distance, limit, and taking into account the limited capacity of the fleet vehicles. The problem requires an effective solution in almost real time. We propose a new heuristic to provide efficient solutions within this strict computational time constraint. To test the quality of the heuristic, we have developed and validated a Genetic Algorithm (GA) that obtains high quality (but computationally expensive) solutions. The solutions of the heuristic compare favorably to those obtained by the GA. The latter has also been tested successfully in a real-time fleet management system.