A multiple ant colony system for a vehicle routing problem with time windows and uncertain travel times

In this paper, we study the capacitated vehicle routing problem with time window constraints, under travel time uncertainty. The uncertainty here represents the perturbation on the data caused by the effects of the unpredictable events in the reality, like traffic jams, road constructions, etc. To be able to near-optimally solve the large-instances of this problem without encountering memory errors or without taking too much time, we propose a heuristic approach based on ant colony optimization, which generates multiple solutions at the end of its execution, each solution with a different protection against the uncertainty. The trade-off between robustness and cheapness shown by these generated multiple solutions are then discussed.