中文摘要：

为了有效地优化城市公交网络，综合考虑了乘客和公交企业的利益，建立了双层优化模型。上层模型考虑整个公交系统的利益，以乘客出行和公交企业运营费用最小为目标，下层模型作为辅助，以乘客直达率最大为目标，尽量减少总的换乘次数。针对该模型设计遗传算法进行求解，并给出算法的具体实现步骤。最后考虑定长设线的方法，设计一个简单的算例，给出不同站点数量的线网的优化方案，并对优化结果进行了对比．验证了模型和算法的有效性。

英文摘要：

In order to optimize the urban transit network effectively, considering the benefits of passengers and bus companies, a bi-level programming model is formulated. Considering the total benefits of transit system, the upper level aims at the minimum cost of passengers and bus companies operation. Meanwhile, the lower level takes the maximum direct-transport as objective with decreasing the total transfer times at most. Genetic algorithm is designed to solve this model and the solution steps are presented concretely. Finally, considering the network optimization method of fixed station number for a numerical example, the paper works out the network optimization outcomes with different number of stations, makes relevant contrast, and shows the efficiency of the model and algorithm.