Strategies for the low-carbon ‘direct rail-sea transshipment’ mode in ports under policy intervention and integrated pricing mechanisms: a three-party evolutionary game and simulation analysis

Rail-Sea Direct Transport at ports can significantly enhance intermodal efficiency and reduce carbon emissions by minimizing transshipment at storage yards. To address coordination challenges among government, ports, and intermodal operators, this paper constructs a three-party evolutionary game model treating the yard fee rate as an endogenous variable. Through replicator dynamic equations and Jacobian matrix eigenvalue analysis, stability conditions for equilibrium are derived, and the driving effects of key parameters are simulated. Results show that when the yard fee rate falls below a critical threshold, carbon taxes and subsidies become entirely ineffective, and the system cannot converge to the ideal equilibrium. Once the rate exceeds this threshold, the evolutionary speeds of both ports and intermodal operators accelerate as the rate rises. Raising the carbon tax coefficient does not alter the system’s ultimate evolutionary direction but differentially accelerates convergence across agents, with the strongest effect on intermodal operators. Excessive subsidies, conversely, weaken governmental regulatory incentives while suppressing the other two parties. A synergistic combination of yard fees, carbon taxes, and subsidies markedly outperforms any single or paired instrument in evolutionary speed, net government benefits, and emission reduction. Policymakers should therefore establish a multidimensional, coordinated policy system rather than a single tool.