Study On Highway Reconstruction And Expansion Work Zone Based On Traffic Conflict

There were greater potential safety hazards on the highway reconstruction and expansion work zones than normal highways.Traffic safety risk assessment is an important measure to improve the level of traffic safety in construction areas.Traffic conflict technology is an alternative method for historical traffic accident analysis.The paper analyzed and summarized the current technical inadequacy of traffic conflicts and the environmental characteristics of highway reconstruction and expansion work zones,conducts research some aspects from the collection of conflict data,conflict identification indicators,conflict identification methods for small radius curve sections,the severity of conflict consequences and the Bayesian conflict model of road sections in typical work zones.The main research of the paper is as follows:1)In view of the insufficiency of the field observation video photography method used in most of the current traffic conflict studies,which can only collect information from several cross-sections of vehicles to derive traffic conflict data,this paper used high-altitude high-precision UAVs to collect regional videos,and then obtaind a large number of the continuous accurate trajectory data of vehicles according to the video recognition program(Including image calibration,vehicle recognition and vehicle tracking),which were further processed to obtain vehicle motion data and overall traffic flow data.After verification,it was found that the accuracy and reliability of the identified data were relatively high.The initial successful recognition rate and continuous tracking rate were around 90%,and most of the trajectory errors could be controlled within 1m.At the same time,the coordinate data of fixed objects WERE collected,which provides support for the fixed objects conflicts,which was often ignored in previous studies.2)Aiming at the complex road environment where a large number of rear-end,lane changes and fixed objects conflicts coexist in the highway reconstruction and expansion work zone,a combined traffic conflict identification index Ti was proposed.Ti integrates the characteristics and advantages of each traditional single indicator,and overcomes the shortcomings of each single indicator,and can better identify rear-end collisions,lane changes and fixed objects conflicts.Based on continuous vehicle trajectory data,the conflict rate of TTC,PET,DRAC and Ti is calculated,and the conflict-accident correlation analysis is performed.The results showed that the average value of the accident correlation of each indicator under different severe conflict thresholds was: Ti 0.715,TTC 0.681,PET 0.582,DRAC 0.665,and the average value of Ti indicator correlation is higher than the other three traditional indicators.Subsequently,the spatial distribution characteristics of traffic conflicts and accidents of the three typical characteristic road sections are analyzed in detail,and the distribution law of traffic conflicts in typical construction sections is found,and the reasons are analyzed.At the same time,it is found that the location of the serious conflict concentration and the accident point are relatively overlapped,which proves the spatial correlation between the conflict and the accident under the Ti indicator.The results of this study showed that TTC and DRAC were prone to miss many lane change conflicts,PET was prone to misjudgments for rear-end collisions with faster vehicle speeds,and the information content of PET is lower than other indicators.At the same time,none of these traditional indicators considered the fixed objects conflicts.The combination Ti can overcome these shortcomings,and Ti has the highest correlation and its safety evaluation ability is also strong.3)There are a large number of lane transition sections in the reconstruction and expansion work zone,and the transition section is a small radius curve section.In view of the unclear and misjudgment problems in the definition of conflict indicators in traditional Cartesian coordinates on small-radius curved road sections,the Frenet coordinate system is first introduced.Using the characteristics and advantages of Frenet coordinate system,a more suitable small-radius coordinate system is proposed.The paper raised a new method of conflict identification in radius curve section.The process of this method includes: 1)Establishing the Frenet coordinate system according to the centerline of the road(the reference line).Synchronously transform the vehicle trajectory into the trajectory coordinates in the Frenet coordinate system;2)Define the judgment process under each state(car-following /lane change)in the Frenet coordinate system.3)In the Frenet coordinate system,according to the state of the vehicle,the rear-end,lane change and fixed object conflicts are calculated based on Ti recognition.Then the two conflict identification methods "Cartesian coordinate system + Ti" and "Frenet coordinate system + vehicle state determination + Ti" were compared with instance data.Finally,the superiority of this method was verified by data comparison.The new identification method could reduce missed judgments and misjudgments in small radius curve sections,and better identify conflict risks.This new identification method overcomes the problems of unclear definition and misjudgment of conflicts on small-radius curve sections of traffic conflict indicators under traditional Cartesian coordinates,and extends the previous conflict identification of straight line sections to full-line recognition.4)Most of the current studies on the severity of traffic conflicts only considered the possibility of potential collisions caused by conflicts,but ignore the seriousness of the consequences of potential collisions caused by conflicts.At the same time,there are many conflicts in the work zone,and there might no energy to prevent them.Only limited financial,material and human resources can be concentrated on the targeted prevention of conflicts with serious consequences.Therefore,the study of the seriousness of the consequences of traffic conflicts is very important.In response to this problem,a model of the severity of the potential collision consequences of traffic conflicts was derived based on the theory of vehicle collisions.The model takes into account the possibility of potential accidents and the severity of the consequences,and considers the two situations of vehicle-vehicle and vehicle-road fix objects.It is found that the correlation between the conflict rate and the accident rate is 0.585,and the conflict severity rate that takes into account the severity of the consequences has a higher correlation with the accident severity rate that considers the severity of the accident consequences,reaching 0.669.Finally,through further analysis of specific work zone cases,it was found that the severity rate of conflicts can better reflect the severity of the consequences of the accident,and it was possible to find out the locations and factors that have a greater rate of conflict severity.5)There was currently a lack of traffic conflict research specific to the scenes of work zones,and work zones of different types of scenes had their own characteristics.In the past,traffic conflict prediction and evaluation models mainly considered the factors of traffic flow,and less considered the road conditions of the work zone and the factors of the vehicles themselves.Therefore,this chapter aimed at the two typical work zones of Jinan-Qingdao Highway—lane transition work zone and single-lane closed work zone.Based on the combination indicator Ti,the whole road alignment recognition method,and the traffic conflict consequence severity model,construct each serious The Bayesian network causality model of the severity of the consequences of the conflict and the road factors in the work zone,the traffic flow and the vehicle’s own factors,conducted inference analysis and analyzes the model results.The results showed that factors such as large vehicles,average vehicle speed,standard deviation of traffic flow speed,radius of circular curve,corner of driving unit length,angle of upstream transition zone,length of working zone and other factors had a significant impact on the serious consequences of conflict.Then introduced the Bayesian network-based vehicle collision risk assessment method,and finally gave targeted suggestions to reduce the probability of severe traffic collisions.and establishes a risk assessment of the consequences of vehicle collisions in each typical work zone.In summary,the paper conducts a traffic conflict study on a typical highway reconstruction and expansion work zone.This research can better identify the conflict risk of the highway reconstruction and expansion work zone,and has important guiding significance for the traffic design and safe operation during the highway reconstruction and expansion work zone.