Strategic plan for China's air high-speed rail express freight network and its carbon reduction potential

The booming development of express freight demand is eager for innovative transportation modes to satisfy the demand for capacity, timeliness, and low carbon emissions. China is working to create an air-HSR fast freight mode based on the continuous expansion of its high-speed rail (HSR) network in an effort to relieve the burden on air freight and lower the emissions associated with it. In this study, a novel freight network design model for the air-HSR planning problem is developed. It combines the centrality of nodes, carbon emissions, and time efficiency to resolve the trade-offs between time efficiency and carbon emissions. This research supports the planning decision and the viability of the air-HSR mode. The hub location decision and initial air-HSR express freight network plan for China are obtained by using the traversal search algorithm and real case data. We then further examine the carbon emission reduction potential that the air-HSR intermodal express network can generate compared with the airline network. However, since the real problem is more complicated and involves many stakeholders, the carbon reduction potential is calculated based on some simplified theoretical assumptions to obtain specific quantitative results. The results indicated that the planned air-HSR network could provide express service nationwide in 24 h, while the carbon emission was reduced by 2.08 million tons, which is a 57.35% reduction compared to the original airline network, and saved the entire transportation sector 498.7 million RMB. Additionally, carbon emissions have decreased across each city pair, notably in the central and eastern areas where there is a substantial possibility for carbon emission reduction.