Abstract: One important issue of probe vehicle traffic information collection is how to determine the sample size，under the premise of ensuring the traffic information received by GPS equipped probe vehicles accurate and reliable.In consideration of the validity of data，probe vehicle speed，sampling time interval，especially the mixed ratio coefficient，it analyzes the effect of mixed ratio coefficient to the sample size.The model of probe vehicle sample size on road network is established by the combination of different types of sample size model.The result shows that：compared with the previous model，this one is more reasonable and greatly enhances the ability of the practical application.

Key words: probe vehicle, sample size, sample type, mixed ratio coefficient

摘要： 在保证GPS浮动车获取的交通信息准确可靠的前提下，如何确定浮动车数量是浮动车信息采集技术应用中的一个重要问题。在考虑数据有效性、浮动车运行速度和采样时间间隔等因素的基础上，重点考虑了浮动车样本的混合情况，分析了混合比例系数对样本数量的影响，通过对不同种类浮动车的计算模型进行融合，建立了面向道路网的浮动车样本数量计算模型。仿真实验表明：与前人模型相比，该模型更具合理性，并极大地提高了模型的实际应用能力。

关键词: 浮动车, 样本数量, 样本种类, 混合比例系数