Synergistic integration of fragmented transportation networks: When do networks (not) synergize?

The transportation of information, goods, people, and other entities inevitably experiences fluctuations in demand and supply, which results in the underutilization of certain links within a transportation network while other links are fully utilized and unable to accommodate any additional demand. A promising strategy for leveraging these links is the collaborative integration of fragmented transportation networks to facilitate access between isolated nodes. We present a novel analytical framework for examining the conditions under which such network integration would enhance the overall transportation efficiency. We conducted comprehensive numerical experiments to investigate the influence of the network structure on the synergistic effects of network integration with a focus on the link survival ratio and dissimilarity between networks. The results showed that networks comprising nodes with relatively uniform importance benefit significantly from network integration whereas core–periphery networks are less likely to benefit. Based on our findings, we propose an indicator for predicting the potential for synergistic effects that is related to the growth rate of the giant component. This study contributes understanding of transportation network dynamics and offers practical insights for optimizing network integration strategies to leverage underutilized capacities and improve various types of transportation systems.