Study On Traffic Flow Characteristics Of Interchange Merging-Areas Basing On Traffic Safety

Freeway interchange merging-area is a bridge which connects the ramp and main lanes.It is a concentration area of lane changing behavior.Since merging behavior is different from common lane-changing behavior,it has a remarkable influence on the flows of main lanes.Therefore,the merging-area has become one of the bottlenecks of the entire freeway system.In order to study the formation mechanism of the bottleneck,this paper will study the traffic flow characteristics from the perspective of traffic safety.Using traffic conflict techniques,this paper aims to establish the relationship between traffic flow and safety condition.First of all,literature review was performed to better understand the development of relevant researches.On this basis,this paper proposed a detailed investigation plan considering the investigation time,manpower,safety and other factors.Maqun hub was selected as the investigation object of which the road design parameters and traffic flow were observed.The trajectory tracking software was utilized to collect sufficient traffic conflict samples.By analyzing the field collected data,traffic flow characteristics of the merging-area were grasped and safety situations at different segments were studied.The typical characteristics of traffic flow were selected from the perspective of safety.VISSIM simulation software was then adopted to study the traffic flow characteristics and safety conditions at different segments of merging-area.The field collected data were used to test and calibrate the simulation model.According to the results of the simulation experiments,this paper studied traffic flow characteristics under different road and traffic conditions.Specifically,the traffic flow characteristics under different acceleration lane lengths were analyzed to find the traffic flow patterns at different segments of the merging-area.After the analysis of traffic flow,a safety assess,ment index was determined based on traffic conflicts.Finally,this paper described the relationship between the safety assessment index and crash data using an exponential function,with which the corresponding accident rate and conflict amount can be calculated.A safety level classification standard was then proposed based on the value of velocity standard deviation coefficient.