Recognition Of Mandatory Lane Change And Crash Risk Analysis In Multi-lane On-ramp Merging Area

As an important part of the continuous flow facilities,the on-ramp merging section of the urban expressway assumes the function of the on-ramp vehicles merging into the main line.The vehicles interweave with each other in a complex way,which is an important factor restricting the capacity of the road network.The on-ramp and main line merge area of urban expressway is also one of the most common traffic bottlenecks,with a large number of vehicles passing,high-intensity vehicles interweaving,frequent vehicle lane changing and traffic congestion,results in a high risk of traffic accidents in this area.In the study of bottleneck traffic flow in the existing merging area,the on-ramp is mostly a single lane.However,there are significant differences in lane changing demand intensity,lane changing decision-making mechanism and lane changing safety risk in the multi-lane on-ramp merging area.Previous studies have not revealed the lane changing behavior and safety risk characteristics in the multi-lane on-ramp merging area.In addition,most of the previous studies on lane changing behavior in the merging area adopted driving simulation and traffic simulation methods,which lacked the data basis in line with the actual requirements and were quite different from the driver behavior in the real road scene.The vehicle trajectory data can overcome the above defects and provide the foundation support for the deep excavation of traffic flow theory and lane changing behavior.Therefore,the traffic flow characteristics and lane changing behavior characteristics of multi-lane on-ramp merging area are studied in depth with the vehicle trajectory data in this thesis.To understand the mechanism of mandatory lane change,a method of mandatory lane change phase recognition and safety risk analysis was established.It has important engineering application value to guide the safe operation of vehicles in the multi-lane on-ramp merging area.The main research contents of this thesis can be divided into the following aspects:First of all,the research scope and vehicle operation characteristics of the multilane on-ramp merging area are defined.High resolution extraction and processing of road traffic operation and vehicle trajectory data in multi-lane on-ramp confluency area are realized by using UAV and video automatic vehicle trajectory extraction technology.Based on the traffic flow theory,the temporal and spatial characteristics of the traffic flow parameters of the multi-lane on-ramp merging area are analyzed,and the bottleneck characteristics of the multi-lane on-ramp merging area are studied.Secondly,based on the vehicle trajectory data,the mandatory lane change types of vehicles in the multi-lane on-ramp merging area are distinguished.Starting from the division of vehicle lane change phase,the vehicle lane change data is obtained by identifying the feature points of vehicle mandatory lane change.Combined with the micro behavior parameters of vehicle mandatory lane change,the law of vehicle mandatory lane change was analyzed from the aspects of vehicle mandatory lane change demand intensity and lane change decision mechanism.Thirdly,the use of multi-class SVM method,through to the mandatory vehicle lane-changing behavior related characteristic variables were normalized and dimension,using radial basis as the kernel function of SVM,using the grid search algorithm of optimum combination parameters calibration,with two different compulsory lane changing types of lane changing vehicle lane changing phase recognition.Finally,the stopping sight distance and stopping distance index are selected as the surrogate safety measures,and the fault tree analysis method is used to systematically evaluate the safety risk of mandatory lane changing based on the degree of risk exposure and risk severity,so as to improve the safety risk recognition of multi-lane on-ramp merging area.According to the results of safety risk,the influence of lane changing speed,mandatory lane changing type and execution position on the safety risk of mandatory lane changing is analyzed comprehensively,which provides reference for the design of vehicle lane changing auxiliary system and the formulation of security control measures for multi-lane ramp merging.