Research On The Traffic Conflict Mechanism In Freeway Interchange

With the rapid development of highway in China, the road traffic safety become increasingly prominent. As highway traffic conversion nodes and its complicated structure, interchange often become accident-prone points. So traffic safety issues of interchange need further study. Safety analysis method based on the traditional traffic accident requires lots of accident data. Because of a nice correlation between traffic accidents and conflicts, the traffic conflict analysis of interchange safety is of great significance. Therefore, in this article, the main content is analyzing the formation mechanism of traffic conflict in interchange, and finding the reasons of generating conflicts and the origin of traffic insecurity status. The research on the relationship between conflicts and factors lay the foundation for safety evaluation and diagnose of interchange with utilizing traffic conflict technique.Firstly, after a vast amount of literatures reviewed, it points out problems in the filed of the interchange security and traffic conflict technology and the line of research papers is determined. This article selects MaQun hub in Nanjing as object of investigation. The UAV aerial photography technique was used in the investigation of weaving, merging areas and diverging area. Through video processing technology, traffic data is acquired by video processing technology, that including traffic volume, traffic composition, vehicle speed and percentage of traffic flow. The analysis of characteristic of traffic flow lays the foundation for microscopic traffic simulation and traffic conflict mechanism research.Secondly, traffic conflicts occurred in interchange are classified by the angle of conflict, severity of conflict and traffic trajectory. The time to collision (TTC) is selected as the conflict indicator, and the cumulative frequency curve of TTC of conflicts were drawn. The 85% value of the cumulative frequency curve determined rear-end conflict and land-changing conflict threshold of serious conflict and general conflict and the threshold of non-serious conflicts with non-conflict. As traffic conflicts that affected by multiple factors is difficult to obtain, this article is based on VIS SIM, that commonly used software in traffic microcosmic simulation, to acquire conflicts data. Driving behavior parameters in VISSIM are calibrated by survey data and its validation is verified using interval travel time and rate of conflicts. The aim to analyzing the traffic conflict mechanism as the main theory is to find the causes and process of generating conflicts. Traffic flow characteristic and geometric design are only two controllable factors among all factors. Using VISSIM simulation software, traffic conflict data is obtained and its development trend is analyzed under the influence of a single factor changing. Thus it's established relationship between traffic flow characteristic and geometric design parameters and traffic conflicts.