Multi-trip vehicle routing problem with stochastic demands

We consider a version of vehicle routing problem where the vehicles are dispatched multiple times a day for product delivery and the orders (demands) arrive randomly throughout the day. There are two types of decisions, order assignment decisions and dispatch decisions. An order assignment decision decides how the orders are assigned to vehicles but the assigned orders are not dispatched until a dispatch decision is made which gives a vehicle routing plan to fulfill the delivery. A general framework is presented and then two variations are studied. For each variation, a stochastic programming model is proposed and a solution procedure is developed. Preliminary results show that our solution procedures achieve significant improvement over the current practice