A hybrid routing strategy based on carbon emissions in multi-layer networks

Abstract In response to the ‘Dual Carbon’ goals (China’s strategy of ‘carbon peak and carbon neutrality,’ aiming to reach peak carbon emissions by 2030 and achieve net-zero carbon emissions by 2060), this study proposes a Carbon Emissions and Closeness Centrality Hybrid (CCH) routing strategy for multi-layer transportation networks. The strategy integrates node closeness centrality and carbon emissions metrics into a tunable cost function, enabling the balanced optimization of traffic capacity and environmental performance. The three-layer architecture—comprising logical, low-speed, and high-speed physical layers—emulates real-world multimodal systems, where inter-layer coupling reflects mode transfers, such as between subway stations and major bus stops. Simulation results indicate that when the parameter β is approximately 0.8, the system reaches an ideal state. The CCH strategy outperforms the conventional Carbon Emissions Hybrid (CEH) method (a path optimization approach that only considers node degree and carbon emissions), increasing traffic capacity by up to 17.8% in large-scale networks ( N = 1000). Moreover, the carbon emission ratio consistently remains below 1 across different network scales, confirming the strategy’s effectiveness in achieving a sustainable balance between throughput and low-carbon objectives.