Abstract: The distribution center is usually far away from the city center because of the limitation of its location, the land cost and so on, as well as the limited funds of the logistics enterprises or traffic congestion. To reduce the routing number and vehicle distance from distribution center, the multi-temperature joint pickup for suppliers and joint distribution for retailers with virtual linehaul-feeder depot vehicle routing problem within time window constraints(LFVRPTW) is studied. The optimization model is to minimize the total system cost, including vehicle dispatching cost, vehicle running cost，cooling cost，penalty cost for breaching time window，carbon tax cost, insulated box cost and less than one box cost. Assuming that in the system, one distribution center that uses large vehicles for pickup of the cold chain goods for suppliers, one virtual depot that uses medium vehicle to distribute cold chain goods for a certain customer and to provide linehaul-feeder for small vehicles to reload cold chain goods for retailers, other small vehicles distribute goods directly from distribution center to retailers. All the pickup and delivery adopts cold accumulation mode and the virtual linehaul-feeder depot is selected according to lowest cost. Then, an improved ant colony system algorithm is designed to solve the model, which includes pheromone concentration, initial solution by greedy strategy, path selection and hybrid pheromone updating, and the effectiveness of the model is verified by a simulation example of 20 retail stores and 6 seafood suppliers. It is found that (1) the number of lines in the LFVRPTW is lower than that of the VRPTW; (2) less restricted time window constraints can benefit to LFVRPTW; (3) the total cost of the LFVRPTW is lower than that of VRPTW; and (4) the cold accumulated multi-temperature joint pickup and distribution with virtual depot is conducive to the construction of both economical and environmental cold chain system.

Key words: cold accumulation mode; multi-temperature joint pickup and distribution; virtual linehaul-feeder depot; VRP