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行程时间的不确定性是影响货运车队路径选择的一个重要因素，特别是对于要求货物准时送达的配送任务（例如商品混凝土的配送），提出了在车辆调度中考虑由拥挤路段交通流量波动引起的行程时间不确定性的方法，建立了考虑行程时间可靠性要求的车辆优化调度数学模型，给出了相应的启发式算法，通过算例介绍了该模型和算法的应用。结果表明配送总成本随行程时间可靠性要求的提高而增加。

Optimizing Vehicle Fleet Management with Travel Time Reliability Constraint

Although uncertainty on travel time is an important aspect of routing for many freight carriers, the existing works on goods vehicle fleet management problem do not take into account the uncertainty on travel time resulting from the fluctuations of traffic flows on congested roads in urban road network. This paper introduces the constraint of the travel time reliability into the goods vehicle fleet management problem particularly for the just-in-time delivery of goods such as the ready-mixed concrete. The mathematical model formulation of the reliability-constrained vehicle fleet management problem is presented together with the heuristic solution algorithm. An example network is used to illustrate the applications of the proposed model and solution algorithm. It was found that the total travel time of goods vehicle fleet is increased when the required travel time reliability is increased.