## 1 Introduction
This intermodal transport can save remarkable time and costs, as well as improving comfort and safety. Moreover, intermodal transport can eliminate the need for constructing lengthy subways or municipal roads. Fast and efficient intercity railways and high-speed trains are used for long-distance travel, improving transportation efficiency while reducing dependence on expensive subways and urban elevated expressways. As a result, the overall cost-effectiveness of transportation infrastructure is significantly enhanced. However, transportation infrastructure in megacities is constructed and managed by different departments. Different transportation infrastructure is often planned, constructed, operated, and maintained independently, without considering interdependence and the overall impact on the integrated transportation network in megacities. This independent approach has caused significant duplicate constructions, resulting in the waste of resources and funds [9]. Additionally, the independent planning, construction, operation, and maintenance of megacity transportation infrastructure are almost incapable of optimizing the overall transportation system for intermodal transport, reducing the overall effectiveness of the transportation network [10]. Compared to the construction, operation, and maintenance phases of transportation infrastructures in megacities, the planning phase is the most important and simple part for achieving intermodal coordination in transportation infrastructure. In terms of importance, the planning phase serves as the foundation for subsequent phases. Implementing coordinated planning for multiple transportation infrastructures can create a feasible basis for coordinated construction, operation, and maintenance [11]. In terms of simplicity, there are significant differences in the construction, operation, and maintenance of different transportation infrastructures. Different transportation infrastructures, as well as the phases of construction, operation, and maintenance, are often implemented by different departments. In the planning phase, there are many commonalities in the planning tasks involved in different transportation infrastructures, indicating that the same planning department can often handle the planning work for different types of transportation infrastructure [12]. The key to the coordinated construction of transportation infrastructure in megacities lies in the coordinated planning of such infrastructures. There is an urgent need for a coordinated planning approach for the multiple transportation infrastructures in megacities worldwide. The current situation and unique characteristics of various transportation modes should be considered in the planning phase to avoid functional duplication and overlapping routes. The advantages of different transportation infrastructures should be maximized to improve the operational efficiency of existing infrastructures and significantly reduce construction and maintenance costs. Therefore, the financial challenges posed by the planning and construction of transportation infrastructures can be managed, and the service capacity of transportation networks can be improved. Meanwhile, service gaps and voids in the transportation infrastructure have been avoided, enhancing efficiency and ensuring fairness in public services. Although the importance of coordinated planning for transportation infrastructure has become very evident in megacities, a widely accepted method for coordinated transportation planning has not yet been established. This study aims to analyze this complex issue and propose a novel method for the coordinated planning of transportation infrastructure in megacities based on Agent-AI dynamic simulation. This approach aims to promote the development of multimodal transportation infrastructure planning and attempts to address the marginal effect of transportation infrastructures in megacities. The rest of this paper is organized as follows. In the Section 2, existing relevant studies will be reviewed.