Modeling Real-time operations of Metro-based urban underground logistics system network: A discrete event simulation approach

Fast-growing logistics demand aggravates traffic congestion while posing great pressure on the urban ecology. A prospective solution is to split extensive goods movement from roads to underground, especially the metro systems. This paper proposes a simulation-based approach for supporting the operational decision-making of the metro-based urban underground logistics system (M−ULS). Based on a holistic concept of M−ULS network archetypes, two integration schemes of passengers and freight transport in metro network (i.e., collinear-detached metro and the collinear-trailer metro) are explicated. Next, mechanisms of metro freight service assignment, standardized packing, timetable coordination, and rolling stock circulation are proposed and formulated considering multiple criteria and travel patterns. A data-driven discrete-event simulation model with user interface is developed to acquire the real-time operating states of M−ULS in 36 tested scenarios. Experiments conducted on the Nanjing Metro case show that the proposed method can effectively capture the dynamic performance and bottlenecks of network operations in different operating periods and environments. The two considered system schemes show respective advantages in terms of freight demand backlog, capacity, traffic flow control, and efficiency, both of which have good compatibility with metro passenger services. The value of this paper is to provide a quantifiable design framework and assessment paradigm for M−ULS operations. It also offers new insights for solving “big-city diseases” and the potential innovations of urban underground space and metro systems.