School of Traffic and Transportation, Beijing Jiaotong University, Beijing, China.
Department of Transportation, China Railway Guangzhou Group Co., Ltd., Guangzhou, Guangdong, China.
PLoS One. 2018 Oct 10;13(10):e0204598. doi: 10.1371/journal.pone.0204598. eCollection 2018.
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.
不定期列车，其运营频率随货运需求波动；以及定期列车，它们的运营基于类似于旅客列车的定期时刻表。定期列车的时刻表一旦确定就会向公众公布，不受货运需求的影响。通常，定期列车的总容量可以满足快递货物的预测平均需求。然而，在实践中，需求总是在变化。因此，如何将货物分配到定期和不定期的列车服务已成为铁路运输面临的一个重要问题。本文关注于混合列车服务网络中铁路快递货物分配的协调优化。在充分利用定期列车服务容量的前提下，我们提出了一种车到列车的分配模型，以合理地将铁路快递货物分配到定期和不定期列车上。目标是最大化运输铁路快递货物的利润。约束条件包括服务弧的容量限制、流量平衡约束、运输截止日期约束以及决策变量之间的逻辑关系约束。此外，我们讨论了一种线性化技术，将非线性的运输截止日期约束转换为线性约束，使其可以通过标准的优化求解器求解。最后，基于京广铁路线进行了一个实例研究，以验证所提出解决方案的有效性和效率。
