Optimizing the Service Network Design Problem for Railroad Intermodal Transportation of Hazardous Materials

Abstract

The service network design problem is one of the key problems in the field of railroad intermodal transportation of hazardous materials (hazmat). It lies in determining the frequency of the trains and the allocation of both hazardous and ordinary shipments to these trains, as well as the railroad connecting plan of all shipments based on the established train formation plan. Based on a unified method, we build a multiobjective mixed-integer linear-programming model that comprehensively considers both hazardous and ordinary materials, the compatibility of goods and services, the capacity of the transfer station, and the delivery time limit of each shipment. An augmented ε-constraint algorithm is customized to solve the model. Computational results of a practical example in China show that an increase of 8.4 million yuan in the total cost could reduce nearly 24541 the total risk. Moreover, the algorithms comparison and sensitivity analysis indicate that the augmented ε-constraint algorithm is a more suitable approach to handle the model because of its advantage in the uniqueness of distinct nondominated solutions. Finally, the sensitivity analysis shows that the total cost and risk could simultaneously be reduced if the delivery time limit is relaxed or if the transfer time is shortened.

Metamodel-Based Optimization Method for Traffic Network Signal Design under Stochastic Demand

“…In the metamodel ftting step, based on the current sample of average equilibrium fow, the metamodel is ftted by solving the optimization problem (9). Ten, the signal control optimization step uses the ftted metamodel as constraint (6) to solve the signal control design problem and derive the optimal signal settings g t . Further, the updated signal settings are implemented in the expensive calculation process, which leads to a new calculation result of the average equilibrium fow x ave t .…”

“…Trafc network design is a basic means to improve trafc fow distribution and alleviate trafc congestion in urban trafc networks. Te network design problem (NDP) is usually to determine optimal network supply decisions, such as adding new links or improving the capacity of existing ones, with certain objectives (e.g., maximizes social benefts or minimizes total travel cost), while considering users' route choice behavior [1][2][3][4][5][6]. Tere exist diferent network supply decisions for the trafc network design problems, including road network expansion design, signal control optimization design, and road tolling design.…”