Abstract
A freight train service network generally involves two categories of trains: unscheduled trains, whose operating frequencies fluctuate with the freight demand, and scheduled trains, which are operated based on regular timetables similar to passenger trains. The timetables for scheduled trains are released to the public once determined, and they are not influenced by the freight demand. Typically, the total capacity of scheduled trains can satisfy the predicted average demand of express cargos. However, in practice, the demand always changes. Therefore, a method to assign the shipments to scheduled and unscheduled train services has become an important issue faced in railway transportation. This paper focuses on the coordinated optimization of rail express cargo assignment in a hybrid train services network. On the premise of fully utilizing the capacity of scheduled train services, we propose a car-to-train assignment model to reasonably assign rail express cargos to scheduled and unscheduled trains. The objective aims to maximize the profit of transporting the rail express cargos. The constraints include the capacity restriction on the service arcs, flow balance constraints, transportation due date constraints and logical relationship constraints among the decision variables. Furthermore, we discuss a linearization technique to convert the nonlinear transportation due date constraint into a linear constraint, making it possible to solve by a standard optimization solver. Finally, an illustrative case study based on the Beijing-Guangzhou Railway Line is carried out to demonstrate the effectiveness and efficiency of the proposed solution approach.
Highlights
In recent years, the competition between railway and highway transportation has become increasingly intense, especially for the long-distance transportation of high-value freight
We study the car-to-train assignment problem of rail express cargos on the mixed scheduled and unscheduled train services network and conduct an illustrative case study based on the Beijing-Guangzhou Railway Line
The contributions of this work to the existing research literature can be summarized as follows: 1. The operating frequencies of the unscheduled trains fluctuate with the freight demand, while the scheduled trains are operated based on regular timetables similar to the passenger trains; this paper coordinately considers the train service network that involves both the unscheduled trains and the scheduled trains
Summary
The competition between railway and highway transportation has become increasingly intense, especially for the long-distance transportation of high-value freight. Based on our previous estimation, the transportation demand of high-value freight is very large and is far beyond the supply of the 156 train services. In this situation, it is necessary to improve the railway freight transport service to attract more freight flow from the road. It is an important task to evaluate whether the train service plan is reasonable enough as well as globally optimize the car-totrain plan using state-of-the-art methods These important tasks were traditionally done manually, but there is an increasing move toward automated software based on mathematical models and algorithms. Optimizing the car-to-train assignment for the rail express cargo is an important problem that needs to be addressed both theoretically and practically
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