| As an important part of daily life,transportation plays a pivotal role in the development of the national economy.In recent years,compared with the continuous growth of the number of motor vehicles in China,the expansion speed of road space is relatively slow.As a result,traffic congestion problem has become serious increasingly.In the limited road space,how to make full use of the existing traffic management equipment to improve the efficiency of traffic flow and avoid the occurrence of traffic congestion is the current research focus in the field of traffic control.In this context,compared with the temporal and regional characteristics of traffic congestion,the dissertation studies the optimization methods of preventing over-saturation for the regional road network based on the limited storage capacity of the existing road space,and the main work completed is listed as follows:1.Aiming at the problems of poor clustering quality and rough division in the cluster-based traffic segmentation method,a traffic segmentation method based on image segmentation algorithm is proposed.According to the coverage of daily traffic flow distribution,the daily traffic flow is divided into three modes,then the traffic flow data under different modes are divided into time periods to reflect the difference in traffic travel characteristics of different working days and rest days,and improve the division accuracy.Aiming at the interference of subjective factors in the manual division method,the advanced FR-FCM(Fast and Robust Fuzzy C-Means Clustering Algorithm)algorithm is used to segment the traffic flow data image.The operation process of this method is simple and easy to implement,and the result of the division is visualized.The traffic time division method based on the image segmentation algorithm is based on the change trend and the value of the traffic flow to make objective and scientific division,which avoids the drawbacks of the manual division method effectively.2.Aiming at preventing over-saturation of critical intersection in the regional road network,the Same Entrance Full-Pass(SEFP)control method is proposed and applied to the critical intersection,which forms three-turn vehicle streams coming from the same entrance of the intersection into one signal phase,and releases or stops them at the same time.The new method can improve the safety and efficiency of traffic operation at the critical intersections.In addition,this method can avoid traffic conflict problem in the traditional two-phase control method effectively and the unfair queuing on adjacent lanes in the traditional four-phase control method.3.On the basis of analyzing the characteristics of the traffic flow between the critical intersection and its adjacent intersections,the related three-turn traffic flows control method is proposed and applied at the adjacent intersections,providing service for the critical intersection,that is,releasing suitable traffic volume to each critical intersection entrance according to its demand,avoiding the overflow on the section of the critical intersection.Combined with the theory of traffic waves,a coordinated control scheme based on signal phase difference is developed at adjacent intersections,which can reduce the vehicle delays and stops,and increase the throughput of the critical intersection.At the same time,a control method of "incomplete" interception is proposed,avoiding the saturation of the critical intersection and lays a good research foundation for preventing over-saturation of the regional road network.4.A method for grouping intersections within the regional road network based on overlapping division is proposed to address the shortcomings existing in the conventional road network division methods.This method considers the characteristics of vehicle flow between the adjacent intersections fully,and forms them into one control group.On this basis,the dynamic vehicle distribution rate on the central intersection entrance section of each control group is derived,and a new calculation method for the capacity of the regional road network is designed,providing a reasonable threshold for the flow control at the boundary intersections.In order to avoid excessive vehicles entering the regional road network,causing vehicle stagnation and congestion,the boundary flow control strategy of "reducing input and increasing output" is proposed and implemented at the boundary intersections.When the number of vehicles in the regional road network exceeds the threshold,the "incomplete" interception control method is adopted at the I-type central intersections at the boundary to reduce the number of vehicles entering the regional road network.At the same time,the releasing phases of the II-type central intersections at the boundary are switched to the vehicle-output phases,discharging the vehicles from the regional road network in time.The flow limit control method adopted at the boundary intersections has a significant effect,maintaining the number of vehicles in the regional road network within a rational range and avoiding the over-saturation of the regional road network effectively.5.The cooperative control strategy of "boundary service center" is proposed and applied to the intersections in regional road network.Based on the implementation of the timing control plan for I-type central intersections,a two-level fuzzy control model is established at the boundary intersections in I-type control group,which are also the II-type central intersection,so the releasing right and releasing time of each phase in II-type intersection can be adjusted dynamically to coordinate the traffic conditions of the relevant road sections by considering the release requirements of each I-type intersection entrance and the queuing situation on II-type intersection entrance sections at the same time.This control method not only ensures half of the intersections in the regional road network realize the optimal control of the maximum traffic volume,but also reduces the difficulty of coordinated control of the intersections in the regional road network,making it easier to implement and applications.The micro-traffic simulation software is used to build the traffic mode.Through simulation experiments,the simulation results of various optimization methods are analyzed and compared,verifying the feasibility and effectiveness of the optimization control methods proposed in this dissertation. |
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