Robustness Evaluation and Optimization of China’s Multilayer Coupled Integrated Transportation System from a Complex Network Perspective

With increasing exposure to natural hazards and anthropogenic risks, the robustness of transportation networks must be enhanced to ensure national security and long-term sustainability. However, robustness-optimization research has mainly focused on single-layer networks, while the systematic exploration of multilayer networks that better reflect real-world transportation system characteristics remains insufficient. This study establishes a multilayer integrated transportation network for China, encompassing road, railway, and waterway systems, based on complex network theory. The robustness of single-layer, integrated networks and the integrated transportation networks of the seven major regions is evaluated under various attack strategies. The results indicate that the integrated network exhibits superior robustness to single-layer networks, with the road sub-network proving pivotal for maintaining structural stability. Under the same edge addition ratio, the robustness improvement achieved by the low-importance node enhancement strategy is, on average, about 80% higher than that of the high-importance node strategy, with the effect becoming more significant as the edge addition ratio increases. These findings provide theoretical support for the vulnerability identification and structural optimization of transportation networks, offering practical guidance for constructing efficient, safe, and sustainable transportation systems.