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提出了利用感应线圈检测器动态提取饱和流率的方法,前后车辆离开线圈的时间差为车头时距,计算第4辆至最后一辆处于饱和状态车辆的平均饱和车头时距,运用指数平滑法处理历史饱和车头时距与当前周期饱和车头时距。确定了车型及饱和车头时距判断阈值,当线圈占用时间大于小型车平均占用线圈时间2倍时,判断为大型车,小型车的饱和车头时距判断阈值为历史平均值加1s,大型车的饱和车头时距判断阈值为历史平均值加5s。用VISSIM软件进行仿真,验证提取方法的有效性。仿真结果表明:动态提取方法能减少饱和车头时距突变的影响,当前周期车头时距骤减31.3%,饱和流率仅增加5.6%,5个周期的饱和流率分别为1 782、1 682、1 600、1 690、1 773veh.h-1,而HCM模型的计算结果为1 680veh.h-1。与传统方法相比,该方法能满足动态提取的需求,实施成本低。
The method of using dynamic induction coil detector to extract the saturated flow rate dynamically is proposed. The time difference between the front and the rear of the vehicle leaving the coil is the headway and the average saturation headway time of the fourth to the last saturated vehicle is calculated. The index smoothing method is used Historical saturated headway and the current cycle of the saturation headway. When the occupancy time of the coil is more than 2 times of the average occupancy coil time of the small vehicle, it is judged that the saturated head time judgment threshold of the large vehicle and the small vehicle is the historical average value plus 1 second, and the large vehicle Saturation front time to determine the threshold for the historical average plus 5s. VISSIM simulation software to verify the effectiveness of extraction methods. The simulation results show that the dynamic extraction method can reduce the influence of the sudden change of the saturation headway time. The current headway decreases 31.3% and the saturated flow rate increases only 5.6%. The saturated flow rates of the five cycles are respectively 1 782 and 1 682, 1 600,1 690,1 773 veh.h-1, while the HCM model was calculated as 1 680 veh.h-1. Compared with the traditional method, this method can meet the demand of dynamic extraction and has low implementation cost.