引入服务可靠性这一概念，以乘客出行成本和车行运营成本最小为目标建立随机需求下的 公交网络模型，并提出固定需求的服务方案模型和改进的二阶随机方案模型。该模型体现了乘客 公交出行的选择策略并反映了公交网络中不确定需求和服务可靠性的相互联系。在分析公交出行 网络中的服务设计，包括常规服务和特别服务的基础上，运用二阶下降法通过规定不确定的随机 变量（服务可靠性参数） 来求解二阶随机方案：首先在一阶段减少混合整数规划的数量以节省计 算时间，随后在二阶段中模拟出一个线性规划，以便有效地求解二阶随机方案。最后，通过实例 模型验证了该方案的可行性。

The notion of service reliability was introduced. The public transit network model with the stochastic demand was established through taking minimizing the passengers travel cost and bus opera⁃ tion cost as the target. The fixed demand service scheme model and two-stage stochastic scheme model were put forward respectively. The travel choice of passenger for public transit was embodied while the inter relation between stochastic demand and service reliability was reflected by this model. Then the service design of public transit network was analyzed, including the regular service and the particular service. The two-stage stochastic scheme was solved by using two-stage descent method and defining the stochastic parameter of service reliability. The computing time was saved by reducing the number of mixed integer programming during the first stage, and then a linear programming was simulated to solve the two-stage stochastic scheme during the second stage. Finally, the feasibility of this model was veri⁃ fied with instance model.