中文摘要：

车头时距分布是研究交通流特性的重要方法．本文基于北京市若干交叉口的实测样本数据，研究分析了拥堵状态下信号交叉口的排队车辆越过停车线的车头时距分布及其变化特点，结果表明在第6个车辆之后达到饱和车头时距．在此基础上，针对中心城区拥堵区域次干道以上等级的信号交叉口，提出拥堵状态下的通行能力模型．进一步地，利用实测数据作了案例计算与对比分析，直行与左转车道通行能力的平均误差率分别为2．27％与4．28％，验证了模型的可行性与有效性．此外，该结果优于其它计算方法所得结果，表明在拥堵状态下，该方法的适用性更高．

英文摘要：

Headway distribution is an important way to study traffic flow. Based on the traffic sample data of several intersections in Beijing, this paper analyzes the headway distribution of vehicles which cross the stop in the queue with congestion and its changing characteristic. Result shows that it reaches saturated headway since 6th vehicle. On this basis, a traffic capacity model with congestion is built, and it＇ s for the signalized intersections which are formed by arterial or subordinate roads at city center areas. Further, the data surveyed at some signalized intersections is used for case calculation and contrast. The result is that the average error rates of going straight and turning left traffic capacity are 2.27% and 4.28%, which verifies the feasibility and effectiveness of the model. In addition, the result of this calculation method is superior to others, which shows that the method is of higher applicability in the congestion state.