| With the rapid development of urbanization,the corresponding traffic congestion problem is becoming more and more serious.There are two reasons:(1)the existing urban roads are difficult to meet people’s growing travel demand,and the traffic pressure is great,(2)limited land resources are difficult to achieve large-scale expansion of roads;in order to alleviate the urban traffic pressure,many cities upgrade or expand the urban expressway on the basis of the existing roads.Compared with the ordinary roads,the urban expressway has the advantage of "fast",but it also causes the most concerned traffic safety problems;it is worth our thinking and research that how to effectively manage the operation speed of the expressway,so that it can ensure the safe operation while taking into account the higher traffic efficiency.The paper relies on the general project of National Natural Science Foundation of China "optimization of self-organization mechanism and related design parameters of Expressway continuous interchange traffic flow(No.51878236)" and the scientific research project of Hefei key engineering construction administration bureau "Research on Key Technologies of expressway system evaluation and traffic design(No.2019FFCJ4364)".In order to determine the safety speed limit value and the speed limit method of expressway diverging and confiuence area,firstly,combining the actual traffic flow data of UAV aerial photography,using SPSS,origin and other software as well as single factor analysis of variance,LSD test and other methods to analyze the six characteristics of traffic volume,traffic density,section speed,lane speed,vehicle lane change and traffic conflict,and then a reasonable experimental platform is constructed from three aspects:software selection,driving behavior parameter calibration and scene effectiveness evaluation,at the same time,based on the collected data and relevant standard values,the experimental scheme is designed,and the scheme is simulated by combining with the experimental platform,and the relevant software is used to extract the downstream traffic volume and the number of traffic conflicts,and considering the traffic efficiency and traffic safety comprehensively,taking the difference between efficiency and conflict rate as the evaluation index,the data is analyzed in detail and the reasonable speed limit value of the diverging and confiuence area is determined,finally,based on the actual traffic accident and speed data,the safety level factor index is established and the grade threshold is determined,at the same time,the speed limit guidance method is studied,on this basis,the safety warning and speed limit guidance method is constructed.The results show that:(1)there is a significant relationship between the speed and the traffic volume,the rate of vehicle change,the rate of traffic conflict and the effective lane ratio of diverging and confiuence area,in addition,no matter what kind of traffic demand,the main lane of diverging and confiuence area has a more significant impact on the vehicle speed;(2)taking the efficiency-conflict rate difference as the index,the control variable method is adopted,the reasonable speed limit value of confiuence area is analyzed from three aspects of total traffic volume,main line traffic volume and on ramp traffic volume,and the reasonable speed limit value of diverging area is analyzed from the angles of main line traffic volume and diverging ratio;(3)based on safety level factor and variable speed limit method,the safety warning and speed limit guidance method is constructed,which considers the influence of the reduction of the effective lane ratio of the main line in the confluence area on safety,and the running speed of vehicles in the upstream of the confluence area can be adjusted reasonably,so as to reduce the probability of traffic accidents caused by the traffic bottleneck in the confluence area and improve the traffic safety of the area. |
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