A paired-vehicle recourse strategy for the vehicle-routing problem with stochastic demands

This paper presents a paired-vehicle recourse strategy for the vehicle routing problem with stochastic demands (VRPSD). In the VRPSD, a fleet of homogeneous capacitated vehicles is dispatched from a terminal to serve single-period customer demands, which are known in distribution when planning, but only revealed with certainty upon vehicle arrival. While most existing research for this problem focuses on recourse strategies where each vehicle operates independently, this paper alternatively considers a strategy in which vehicles may be coordinated in pairs. A tabu search heuristic is developed to find good solutions to VRPSD instances with homogeneous customer demand distributions given this alternative recourse strategy. Finally, a computational study on a set of test problems with a variety of demand distributions reveals that the paired-recourse strategy may lead to expected travel cost savings of 3% to 25% on problems with 50 or more customers.