A new paper envisions a multimodal passenger-and-parcel sharing (PPS) network for urban logistics integrating metro, taxi, and truck. A hub-and-spoke structure is designed including hubs located at metro stations and service stores connected to the hubs.
Parcels are transported by metro on backbone links between the hubs and are carried by taxis or trucks between service stores and hubs, depending on the unit costs of these two modes and capacity constraints of the taxi. A mixed-integer linear programming model for hub location problems – fusing the multi assignment p-hub median problem without capacity constraints and the capacitated multi assignment p-hub covering problem – is formulated to optimize the multimodal PPS network.
The model is implemented based on the real-world data in Shanghai (China) under a series of scenarios to evaluate the network performance from two perspectives: the number of hubs and the proportion of taxi drivers who are willing to carry packages.
The scenarios show that with an increased number of hubs, the spatial distribution of hubs disperses from the city center to peripheral areas and more areas can be serviced by taxis. There is, however, a trade-off between the operation cost saved by taxis and the establishment cost of an extra hub. The analysis also presents that if the proportion of taxis willing to carry packages associates with the incentive payments to taxi drivers, an optimal value of incentives exists, by balancing the operation costs of taxis and trucks.
The scenarios show that with an increased number of hubs, the spatial distribution of hubs disperses from the city center to peripheral areas and more areas can be serviced by taxis. More hubs lead to more packages transported by taxi, which reduces the costs on spoke links, but the marginal savings of transport cost declines as well. There is, nevertheless, a trade-off between the operation cost saving by taxis and the establishment cost of an extra hub.