交通分配中转向流量的直接计算方法

为了在交通分配中直接得到转向流量而不是通过事后推算或网络扩展获取,对常规的交通分配算法稍作修改后提出了转向流量的2种直接计算方法.第1种方法基于转向路径关系,其原理类似于路段流量的计算,适用于给出具体路径构成的交通分配算法.第2种方法利用了转向路段关系及其衍生的路段上流量守恒律,是一种改进型Dial算法.这2种方法能避免传统的诸如Furness,Frator模型的事后推算法以及网络扩展法在精度、稳定性和计算量等方面的缺陷,其有效性通过算例分别得到了验证.

Direct computing methods for turn flows in traffic assignment

Two methods based on a slight modification of the regular traffic assignment algorithms are proposed to directly compute turn flows instead of estimating them from link flows or obtaining them by expanding the networks.The first one is designed on the path-turn incidence relationship,and it is similar to the computational procedure of link flows.It applies to the traffic assignment algorithms that can provide detailed path structures.The second utilizes the link-turn incidence relationship and the conservation of flow on links,a law deriving from this relationship.It is actually an improved version of Dial's logit assignment algorithm.The proposed approaches can avoid the shortcomings both of the estimation methods,e.g.Furness's model and Frator's model,and of the network-expanding method in precision,stability and computation scale.Finally,they are validated by numerical examples.