The time window assignment vehicle routing problem (TWAVRP) was recently introduced by Spliet and Gabor (2014). This problem can be viewed as a two-stage stochastic optimization problem (see Birge & Louveaux, 1997). Given a set of customers to be visited on the same day regularly during some period of time (e.g., a season), the TWAVRP consists of assigning in the first stage a time window to each customer before customer demand is known. In the second stage, when demand is revealed for each day of the time period, vehicle routes that respect the assigned time windows are constructed. The assigned time windows have a predetermined width and can start at any time within an exogenous time window that can be customer- dependent