Chaotic Characteristics Of Traffic Flow At Bottleneck Section Of Urban Expressway Under Speed Limit Control

The bottleneck section of urban expressway is an important node in urban traffic network,which has a great impact on the traffic safety and traffic efficiency of the whole road section.In order to solve the problems existing in this kind of node section,some traffic management and control methods such as speed limit control and ramp control are put forward,and positive results are obtained.Speed limit control has received extensive attention among them due to its strong adaptability and operability.In the field of macro traffic flow,there have been many researches on the effect of speed limit control,but most of them are from the point of view of traditional traffic flow theory,and seldom involve the nonlinear and traffic flow chaos;and it is a very meaningful job to analyze the effect of speed limit control on this kind of node section from this point of view.In this study,the bottleneck section of urban expressway is taken as the research object,and the relationship between speed control factors and traffic flow chaos is explored by using chaos theory,simulation and field investigation.The main work of this paper can be summarized as follows:(1)Building simulation model for bottleneck link of urban expressway.According to the characteristics of the bottleneck section,the road sections are divided into three types:?traffic bottleneck caused by the reduction of traffic lanes;?traffic bottleneck caused by confluence;?traffic bottleneck caused by distributary.The traffic flow data of various sections are investigated,and the VISSIM simulation model is established.The model is calibrated and verified,and the reliability of the model is verified;(2)Researching chaotic characteristics of traffic flow at bottleneck section of urban expressway under static speed limit.Using the method of chaotic time series discrimination,changing the speed limit value in speed limit control,speed limit sign position and driver compliance rate,to explore the influence of these3 factors on the chaotic characteristics of traffic flow speed in the bottleneck section of urban expressway,the results reveal the complex nonlinear relationship between the chaotic characteristics and three factors under different scenarios,providing the reference for city expressway traffic flow chaos control.(3)Researching chaos fuzzy control method for road bottleneck area.Firstly,the knowledge base of chaos controller of traffic flow mainline in road bottleneck area is established.Secondly,a traffic flow adaptive neuro fuzzy chaos controller based on traffic flow occupancy,average speed as input and speed limit value as output is established.Whether the traffic flow parameters in the bottleneck area exceed a certain threshold are considered as the starting conditions for the control.Finally,building simulation platform and the optimal starting threshold and the optimal control cycle of chaos control in traffic flow are simulated and analyzed.The validity of the method is verified and the optimal starting threshold and optimal control cycle of different bottleneck sections are obtained.This chapter lays the foundation for analyzing the chaotic characteristics of traffic flow at the bottleneck section of urban expressway under variable speed limit control.(4)Studying on chaotic characteristics of traffic flow at bottleneck section of urban expressway under variable speed limit.The chaotic characteristics of traffic flow velocity under different scenarios are studied by changing speed limit sign position and driver compliance rate in variable speed limit control and the static speed limit control of the corresponding characteristics of comparative analysis.The results reveal the similarities and differences between variable speed limits and static speed limits.