Simulation on the External Benefits and Development of Metro-Based Underground Logistics System : A System Dynamics Approach

The dual utilization of urban rail infrastructures, especially metro network, for collaborative passenger-and-freight transport is gradually being recognized as a sustainable way to conquer many negative externalities caused by the urban freight activities. Based on system dynamic (SD) modeling and simulation, this study aims to assess the environmental and social benefits of the metro-based underground logistics system (M-ULS) under a variety of development scenarios. A SD model is established to integrate several boundaries of M-ULS development, such as investment, operations, externality metrics and market. Beijing, the capital of China, is taken as a case to verify the model and conduct real-life simulation from 2007 to 2035. The results show that the hypothetical M-ULS project with higher funding and capacity leads to greater reduction in the loss of traffic congestion, air pollution, and accidents. Furthermore, during the development stage, the early financial support by government and some policy means for balancing the variations among pricing, supply-demand level and investment do play a significant role in improving system performance. This study can serve as a generic framework for analyzing macro-level development of M-ULS or other sustainable transportation alternatives in a dynamic urban environment