公铁联运规模效应和枢纽拥挤效应的联动分析

Integrated Analysis of Economies of Scale and Hubs Congestion Effect on Rail-road Intermodal Transport

公铁联运最主要的优势就是采用轴辐式网络结构实现规模经济,降低货物的运输成本,货运量越大,规模效应越明显;另一方面,过多的货物在枢纽集结会造成枢纽拥挤,增加货物在枢纽的停留时间,从而降低了公铁联运的竞争力.本文分别采用与流量相关的分段成本函数和M/M/c的排队模型来描述公铁联运的规模效应和拥挤效应,建立了非线性的整数规划模型,用于综合分析规模效应和枢纽拥挤效应对公铁联运的影响.采用混合禁忌搜索算法求解本文的模型,该算法具有较好的收敛效果.最后,分析了铁路服务固定成本、公路运输成本、货物运到期限和枢纽能力对公铁联运竞争力的影响.

The economies of scale which reduce the unit transportation cost is a major advantage of intermodal transport. It indicates that more goods result in a lower unit transportation price. However, hubs become congested on account of too many goods handled in hubs, and it may result in that some goods miss their delivery deadline. This weakens the competitiveness of rail-road intermodal transport. In order to analyze the economies of scale and hubs congestion effect on this intermodal transport synthetically, we use flow-dependent cost function and M/M/c queue model to represent them respectively. Next, we develop a hybrid Tabu search algorithm to solve this nonlinear integer programming, and this algorithm converges quickly. Finally, we analyze how the share rate of rail-road intermodal transport to be influenced by rail connectivity cost, road unit transportation cost, time limit for delivery and hubs capacity.