Prediction Model Of Traffic Conflict In Diverging Area On Expressway

There are a wide range of interchange arrangements for expressways.The interchange can be defined as the road consisting of three parts:the confluence area,the interweaving area and the diverging area.Diverging area is a section near the export ramp where one or more traffic flows are separated from the main line,including the area where the traffic flow is different from the basic section of the expressway.In the diverging area,there are frequent changing lane phenomena in the traffic flow,which leads to the disruption of the traffic flow and the frequent traffic conflict.The interchange has become a prone area for the highway traffic accident.Therefore,how to ensure the traffic safety has become a serious problem of highway interchange traffic safety improvement.In order to analyze the traffic safety situation in the diverging area,traffic accident data are usually used as the basis.However,in some cases,it is not possible to obtain the accident data satisfying the statistical requirements,so that the safety evaluation method based on the accident data is difficult to be used.Therefore,the traffic conflict technology is used to improve the evaluation method of traffic safety.For traffic conflict technology,the effective conflict data is the basis of safety assessment and safety improvement.Therefore,this paper establishes the traffic conflict prediction model of diverging area on expressway.By collecting the characteristics of the diverging vehicle and the traffic flow parameters,the number of conflict in the expressway diverging area can be calculated,which reduces the workload and improves the efficiency of access to traffic conflict data.Around the establishment of the prediction model of traffic conflict in diverging area on expressway,the main research is as follows:1.the data collection method of traffic flow and traffic conflict in the diverging area of expressway interchangeThrough the aerial video observation of the diverging area traffic,different types of data are obtained by using playback.On the one hand,the traffic flow data of the vehicle in each lane,such as the running speed,the headway distance and the changing position,are measured in the interchange of the actual expressway.On the other hand,on the basis of summing up the experience of the predecessors,it is proposed to use the Delphi method to judge the conflict first,and then use the software to measure the TTC value to further test its reliability to ensure the validity of the traffic conflict data acquisition.At the same time,on the basis of collecting the data of traffic conflict,the data of traffic conflict and the data of traffic conflict are collected in order to the study of traffic conflict mechanism.2.Analysis on the characteristics of Traffic Flow and Traffic Conflict in diverging areaAccording to the data obtained from the observation,the basic characteristics of the traffic flow in the diverging area of the expressway are analyzed firstly.It is concluded that the speed and the headway distribution of the main lane are different in each lane of the diverging area.The outermost lane is especially obvious;then the location of the traffic conflict and the outside headway are analyzed.It is concluded that the location of the traffic conflict has a strong correlation with the position of the vehicle lane changing,and the outside headway of the occurrence of traffic conflict is concentrated in a range.3.The traffic conflict formation mechanism based on the gap acceptance theoryBased on the characteristics of diverging vehicle,the diverging behavior of the diverging vehicle is regarded as the process of gap acceptance,and the formation mechanism of traffic conflict is described.It is pointed out that the occurrence of traffic conflict in the expressway diversion area is caused by the fact that the gap of the outside traffic flow is located in a certain interval,which the accepted gap is not big enough or the driver’s fault judgment is caused by the rejected gap,and the calculation method of the critical gap is used to determine the threshold of the interval.4.The prediction model of traffic conflict in diverging area on expresswayBased on the analysis of the vehicle conflict mechanism and the improvement of the gap acceptance theory,the probability of the traffic conflict is calculated by the distribution of the traffic distance and the critical gap.Then the traffic conflict prediction model is established.The model is verified by the measured data.Finally,based on the influence factors of the model,the traffic risk reduction based on the design and management is given.To sum up,based on the actual investigation and data analysis,this paper improves the investigation method of traffic conflict,analyzes the mechanism of traffic conflict,puts forward a new gap acceptance model,gives the parameter calculation method,and establishes the model of traffic conflict prediction.The accuracy of the model is verified by the measured data and the method of reducing the traffic conflict is given.