| 5 | The Probabilistic Traveling Salesman Problem (PTSP) models situations in a delivery context where a set of customers have to be visited on a regular basis (e.g. daily), but all customers do not always require a visit (they have \probabilities" of being visited). In general, every day only a subset of customers requires a visit, and this subset is only known the same day as the required deliveries so re-optimizing vehicle routes from scratch every day is unfeasible. In this situation, the delivery man would follow a standard route skipping the customers that do not require a visit on that day. Therefore, the goal is to fi |