Study On The Safety Assessment Method Of Uncontrolled Intersection With Mixed Traffic Based On Area Conflict Probability

As the development of urban traffic,the problems brought by traffic,especially the safety problem have attracted more and more attention.At present,an intersection is usually assessed and improved based on historical accident data,but there is few methods to assess the safety of an intersection which is newly built or in design phase.Taking uncontrolled intersection as an example,this paper mainly studies the prediction of conflict probability between vehicles and between pedestrians and vehicles as well as its distribution within the intersection,and proposes an intersection traffic safety assessment model and visualization system considering both the conflict probability and severity of potential collision.The main researches of this paper are as follows:Firstly,based on the statistics and analysis of investigation data,the vehicle operation rules can be summarized as arrival rate and lateral migration probability within its trajectory scope.Therefore,the conflict will happen in an area instead of a point.This paper proposes a prediction model of conflict probability between vehicles at uncontrolled intersections considering vehicle size and its operation rules.In addition,the model of kinetic energy loss is built to determine the potential collision severity.Secondly,on the basis of data analysis,a series of rules about pedestrian reaching and then walking through the crosswalk are studied,for example,arrival rate,crossing behaviors and the pedestrian distribution on the crosswalk.Combining with the vehicle operation rules,the prediction model which reflects the conflict probability between pedestrian and vehicle at any position on the crosswalk is built: a prediction model of conflict probability between vehicles and pedestrians at uncontrolled intersections taking pedestrian crossing behavior and their operation rules into consideration.Meanwhile,the vehicle velocity before collision is selected as the representation of potential collision severity between pedestrian and vehicle.Next,this paper proposes a method to assess the safety of uncontrolled intersections considering both conflict probability and severity,which are two major properties of traffic conflicts.The assessing model can be divided into two parts: the first part takes grey cluster model as the main body,and this determines the safety levels as well as their distribution within the intersection;based on the first part,the second part with different performance metrics assesses the safety of the intersection as a whole,and this achieves the comparison between different intersections or schemes.At last,the effectiveness and reliability of the safety assessment model is verified by a real case.At last,an intersection safety heatmap system based on the safety assessment model is presented.The input of the system is the geometric data,vehicle and pedestrian data,while the output would be a safety heatmap.This system achieves the visualization of the assessment results.Then,a case demonstrates the application of the system.The achievements of this paper makes it possible to investigate the hidden danger in advance,enhance the safety according to designing scheme improvement,and reduce part of accidents as well as the pain they will bring.At the same time,this saves the improvement cost.