城市快速路交通流车头时距分布特性分析

Time-headway Distribution Features on Urban Freeway

在对北京市城市快速路实测单车数据分析的基础上,本文发现对数正态分布函数可以成功地对不同速度条件下的车头时距概率密度分布情况进行拟合.运用最小二乘法对该函数进行参数估计,得到不同速度条件下的期望车头时距值以及车头时距的平均值和标准差.结合实测车头时距分布特性,经过修正,发现城市快速路上期望车头时距随速度的变化趋势与高速公路上的测量结果一致,但在定量上却要远高于高速公路上的期望车头时距.最后利用平均车头时距和单车速度绘制出流量—密度和流量—速度关系图,并具体讨论了出入口匝道对外侧车道交通流特性的影响,定量标定了谐动流和自由流相位在不同断面条件下的速度区间.

Based on the analysis of single-vehicle data collected in Beijing 2nd ring of urban freeway, the statistical features of time-headway distribution at different velocities are investigated in this paper, and the time-headway distributions under different velocities are fitted well with the model. In the model, the parameters corresponding to velocity p is estimated to obtain the recommended time-headway, the average time-headway and the standard deviation. Considering the empirical time-headway distribution features, the recommended time-headways on urban freeway at different velocities are discussed quantitatively and qualitatively, and the result is different with the previous investigation works about highway traffic. In addition, the density-flow plane and the velocity-flow plane are plotted in a statistical meaning, then the effect of on/off-ramps on the traffic flow of lane 3 was analyzed, and the velocity thresholds of free flow and coherent-moving flow in different road structures are concluded.