考虑货运方式和客运硬时间窗的地铁客货共车运输优化

Train-shared metro passenger and freight co-transportation optimization considering freight modes and passenger hard time windows

鉴于地铁网络在解决大城市居民出行问题上的成功实践,能否利用非高峰时段地铁线路的冗余运力缓解城市交通拥堵和货运压力,成为近年来城市货运领域的一个热点话题。本文研究了一个基于“客货共车”模式的地铁客货协同运输优化问题,特别考虑了货运需求的运输方式约束(即同一货物运输需求将完全通过地铁完成,或完全不依赖地铁)以及客货需求的时间窗约束,其目标是在必须满足乘客需求的情况下,充分利用地铁运力服务货运需求,同时减少货运对乘客的影响以及混合编组的工作量。货运需求的运输方式约束使得该问题被构建成一个非线性整数规划模型。通过线性化技术,将非线性整数规划模型转化为等价的线性整数规划模型,并利用商业求解器CPLEX进行求解。以北京地铁八通线为例的实验结果表明,所提出的方法能够有效解决所关注的问题,同时所得到的协同优化策略能够提高地铁线路的“客货共车”运输效率。为了进一步说明所考虑的问题特点,相关计算结果与已有研究进行了对比,这为地铁货运管理和决策提供了更多参考。

As a result of the successful practice of metro networks solving the travel problem of residents in large cities,the use of redundant capacity of metro lines in off-peak hours to alleviate urban traffic congestion and freight pressure has become a hot topic in the urban freight field in recent years.This paper explores an optimization problem in metro passenger and freight co-transportation with the“train-shared”mode.It specifically considers transportation mode constraints for freight demands(i.e.,a freight demand either fully relies on the metro or not at all)and time window constraints for passenger and freight demands.The objective is to make optimal use of metro capacity to serve freight demands under the premise of meeting all passenger demands,and meanwhile to minimize the impact of freight transportation on passengers and the workload of mixed train composition.The transportation mode constraints for freight demands result in the problem being formulated as a nonlinear integer programming model.By employing linearization techniques,the nonlinear integer programming model is transformed into an equivalent linear integer programming model,which is then solved using the commercial solver CPLEX.Experimental results using the Batong line of Beijing subway as an example demonstrate that the proposed method can effectively address the problem of interest,and the obtained optimization strategy can improve the efficiency of the“train-shared”mode for a metro line.To further clarify the characteristics of the problem,the relevant results are compared with an existing study,which provides more references for metro freight management and decision.