为加强对高速公路交通运行不稳定状态的控制,基于三相交通流理论,分析亚稳定自由流特性。综合运用交通流基本参数的三维曲面分析、等值线分析和Z型结构基本图分析,分别确定双向6车道、8车道条件下亚稳定自由流的参数阈值,并建立基于亚稳定自由流识别的高速公路不稳定状态预警机制。通过监测、识别、决策、警告4个功能,实现对高速公路交通拥挤和瘫痪的预判和干预。结果表明,对亚稳定自由流的有效识别与预警,有助于提升道路交通管理执法与决策的科学化水平。 In order to strengthen the control over the unstable state of expressway traffic operation, based on the theory of three-phase traffic flow, the characteristics of metastable free-flow are analyzed. Based on the three-dimensional surface analysis of basic parameters of traffic flow, contour analysis and basic structure analysis of Z-structure, the parameter thresholds of unsteady free flow under six-lane and eight-lane conditions are respectively determined and established based on sub-stable free flow identification Highway unstable state early warning mechanism. Through the four functions of monitoring, identification, decision-making and warning, it can predict and intervene on the freeway traffic congestion and paralysis. The results show that the effective identification and early warning of metastable free flow helps to improve the scientific level of road traffic management law enforcement and decision-making.