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基于运行速度的定义,首先通过现场试验采集了试验车的实时行驶速度,分析了试验车的行驶状态变化情况,基于不同的行驶状态确定了车头时距的变化阈值,然后通过研究典型断面的速度波动规律,分析了不同车头时距下的速度变化特征与分布特征,确定出车头时距为自由流状态的度量指标,并通过统计分析方法,提出了车辆自由行驶状态的判别标准。结果表明:自由流交通状态的车头时距应大于9 s;研究结论为公路运行速度体系的建立奠定了理论基础。
Based on the definition of running speed, the real-time running speed of the test car was collected through field test. The change of driving status of the test car was analyzed. The threshold of change of headlamp distance was determined based on different driving conditions. Then, The variation and distribution characteristics of speed under different headway are analyzed. The measurement index of headway from freewheeling state is determined, and the criterion of vehicle free running condition is proposed by statistical analysis. The results show that the headway distance of free flow traffic should be greater than 9 s. The conclusion of the study has laid a theoretical foundation for the establishment of highway running speed system.