Flexibility and consistency in static and dynamic inventory-routing problems

In the Inventory-Routing Problem (IRP) a supplier must deliver commodities to a set of customers over several periods. The objective is to minimize the sum of routing and inventory holding costs. The problem was introduced by Bell et al. in 1983 and has generated increased interest in recent years. We consider IPRs with two new features: flexibility and consistency. In the first case, planned transshipments between customers are allowed. In the second case, constraints are imposed on the spacing of deliveries to customers, on the quantities delivered and on the vehicle delivering to a particular customer.  The problem is modeled as an integer linear program. It is solved by branch-and-cut and by an adaptive large neighbourhood search heuristic. The dynamic case of the problem is also analyzed. Computational results are reported.