对于确定的行车路线，利用随机变量描述公交线路中的行车时间，需要进一步考虑的问题是利用随机过程的知识建立乘客的排队模型，各个站点的队长可用泊松过程在相继到达车辆的时间间隔上的增量来描述。在不同的发车间隔假定下，考虑每个站点在相继到达的车辆间隔内，平均排队长度与发车间隔的关系。

By using random variables to describe the travel times of bus lines on a network diagram, and calculating the mathematical expectation and the corresponding probabilities of the journey time, we can consider the establishment of passengers queuing model by using the knowledge of the stochastic processes. In this paper we consider the relationship between the bus frequency and the average queue length between adjacent time periods at each site for the different assumptions of headuay. 