Research On Modeling Of Intermodal Transport Service Network Optimization

China is experiencing the period of the rapid developments of its multiple transportation modes. The integrated transportation network in China is rapidly developed and improved, and the alternative freight transport modes are increased. Establishment and improvement of an efficient integrated transport system will be our effort direction for the development multi-mode transport in our country. It is also the important foundation of the sustainable development of the social economy and the improvement of the living standard of the people. Furthermore, it is one of the main functional elements of logistics activities. An integrated transportation network with rational layout, scientific management, and efficient operation is strategically important to promote the development of logistics industry in China.The scale of logistics activities is rapidly developing and the level of infrastructure is improving. Meanwhile, it is accompanied by a series of problems, such as low efficiency and high cost of intermodal transportation system. The problems such as unreasonable resources allocation and plain operation design must be solved. The operation management method and construction mechanism does not fit the requirements of rapid development of logistics activities. Coordinate optimization is the management goal of the modern logistics activities based on integrated transport system. Considering the goals and requirements of intermodal transportation system, the study focuses on network optimization and transportation service design. A comprehensive optimization method is proposed from the perspective of strategic planning and tactical planning. The contents of the study are organized as follows.(1) Intermodal transportation hub location and network design The study is proceeding from the perspective of strategic planning. The paper proposes a bi-objective programming formulation for the intermodal transportation network design with multiple stakeholders (network manager, carriers, hub operators and intermodal users). The study represents a given intermodal network as the physical and operational networks. The model incorporates a parametric variational inequality (?) that formulates the mixed equilibrium (UE&SO) behavior of intermodal users in route choice for any given network design decision. The disutility of a carrier link or transfer perceived by an intermodal user is composed of two portions:the actual rate charged by the carrier on the carrier link or hub operator providing the transfer service and the monetary value of transportation or transfer time that equals the actual handling time multiplied with value of time(VOT). In reality, the second portion reflects the impact of congestion on the intermodal operator's route choice. A Cross-Entropy (CE) method embedded with diagonalization algorithm is employed to solve the model. Finally, the developed model is applied to a case study to demonstrate its applicability and gain managerial insights to some extent.(2) Intermodal transportation routing optimization The paper studies the intermodal route choice model and algorithm. The study proposes a multimodal hazmat model that simultaneously optimizes the locations of transfer yards and transportation routes. The capacities of links and transfer yards are embedded into the model. A0-1decision variable is defined which could make the optimization results reflect flow routing. However, it is nonlinear and also contains an absolute term, which makes it very difficult to solve. Several new constraints are introduced to replace the nonlinear and the absolute terms. A Cross-Entropy (CE) method is employed to solve the model.(3) Comprehensive optimization between intermodal transportation network optimization and main line transport service design The study presents an optimization framework for planning intermodal shipments based on hub-and-spoke network. The aim of the research is to minimize the total transport cost from the perspective of network optimization and main line transport service design. The decisions are including hub capacity planning, main line transport services designing, the access to alternate intermodal terminals and main line transport service for shippers and receivers and segments reconstruction. A Cross-Entropy based solution methodology is developed. The optimization framework is applied to problem instances to gain managerial insights. Our analysis indicates main line transport services accounts for a significant portion of transport cost.(4) Comprehensive optimization between intermodal transportation network optimization and feeder line transport service design A two-phase programming formulation is proposed for the simultaneous decision of network optimization and feeder line transport service. The hub location and spoke allocation problem for phase I and the feeder line transport service design problem for phase II. The problem in phase I is formulated as a0-1integer programming model. The problem in phase II is formulated as a vehicle routing problem with time window. A Cross-Entropy based solution method is proposed to solve it. Numerical experiment based on a simple network is carried out to be able to provide detailed model and algorithm outputs to better illustrate how the developed model and algorithm work. In the end, the model is applied to desing hub-and-spoke transpoation network with liner shipping for large-scale example.