基于尖点突变理论的高速公路交通流状态判别方法

Freeway Traffic Flow Condition Criterion Method Based on Cusp Catastrophe Theory

为准确掌握高速公路交通流的运行状态及变化规律,给驾驶人和高速公路管理者提供科学决策依据,通过分析传统交通流计算模型存在的不足,对现有高速公路交通流状态划分方法和基于尖点突变理论的交通流模型进行改进,并引入混沌状态和突变区间的概念,同时添加大车混入率作为改进后的模型参数,得出不同大车混入率下混沌流状态、自由流状态和非自由流状态下的判别标准。以八车道高速公路标准路段为例,借助VISSIM交通仿真软件模拟车流的实时运行状态及变化过程,计算获得仿真情形下不同交通流状态的判别标准和方法。通过对典型高速公路代表性路段实测数据的统计分析,验证了判别标准和方法的合理性与可行性。研究结果表明:交通流在自由流和非自由流状态之间转变时,存在着一种短暂的突变,呈现出一种混沌流的状态;大车混入率对行车速度和时间占有率影响明显,可以对应获得混沌流、自由流和非自由流状态的判别标准;将仿真所获得的交通流状态界定标准与中、美高速公路服务水平划分标准进行对比,自由流状态处于二级或C级及以上服务水平,而且对自由流服务水平的标准要求更高。该方法对于高速公路运营管理、养护路段划分、安全性评价等具有科学、便捷、实用、可行的实际意义。

In order to accurately grasp the condition and the changing law of the freeway traffic flow,and provide the scientific decision-making basis for the driver and the freeway manager,the deficiencies reflected in the traditional traffic flow calculation model were analyzed,and the existing division methods together with models of freeway traffic flow based on the catastrophe theory were improved. The concepts of chaos and catastrophe interval were introduced,whilst the mix rate of the large vehicle was added as the improved model parameters. The criteria of large vehicle chaos flow state,free flow and non free flow state with different mix rates were obtained. Taking the eight-lane expressway standard road as an example,the real-time operation state and changes of traffic flow were simulated by dint of VISSIM,whilst the different traffic flow simulation criterion obtained by calculating. Through the statistical analysisof the measured data of typical freeway sections,the rationality and feasibility of the criterion and method were verified. The results show that the traffic flow changes between free flow and non-free flow condition. During the stage of transformation,there is a transient catastrophe,showing a state of the chaotic flow. The influence of the mix rates of large vehicle on two indicators the driving speed and time occupancy is significant. The corresponding criteria of the chaotic flow,free flow and non-free flow can be obtained as well. Comparing traffic flow state criterion obtained from the simulation with criteria in China and the United States,freeway service has reached the second level or C level and above,and the requirements for the free flow service level are much higher. The method is scientific,convenient,practical and feasible for freeway operation management,the classification of maintenance section and safety evaluation.