中文摘要：

该文以嘉兴境内G15w常台高速和G60沪昆高速各一个路段为对象，进行了双车道和多车道交通流的实地拍摄、车速数据采集和统计分析。发现高货车比例的城际高速公路交通流与城市快速路存在不同的特征，客车与货车具有明显的速度分布差异，总体车辆速度分布呈现双峰特征。提出了一种能够刻画车速分布双峰特征的五参数概率密度函数，其中参数具有清晰物理意义，可以根据具体问题中峰值的不同位置、高度、方差进行调节。三个实测样本拟合优化结果显示，多车道路段两个速度峰值之间的距离比双车道路段更大，而双休日车速（尤其是货车速度）数据的集中程度比普通工作日更高。

英文摘要：

Taking two sections of highway within the borders of Jiaxing from G 15w Changzhou-Taizhou Highway and G60 Shanghai-Kunming Highway respectively as subjects, this article researches into the traffic flow on double-lane and multi-lane by field shooting, speed data collecting and statistical analysis. It is discovered that the traffic flow of intercity highway with higher proportion of freight vehicle is different from that of urban expressway. There is obvious difference between the velocity distribution of passenger car and freight vehicle, and the general vehicle velocity distribution reveals the feature of double peak. Based on these discoveries, it is proposed in this article that a five-parameter probability density function which can depict the double peak feature of vehicle velocity distribution. All the parameters have clear physical meaning and can be adjusted according to different position, height and variance of peak value in concrete problems. According to the result of fitting and optimizing three measured samples, distance between two peak values of multi-lane section is larger than that of double-lane section, while the concentrative degree of speed data （especially speed of freight vehicle） in weekend is higher than that of working day.