Research On The Influence Of Average Speed Dispersion To The Highway Capacity Of Ring Expressway

There are many interchange nodes along the ring expressway,the distribution of ramp is dense with small spacing,the occasional traffic mutations are frequent,the unsteady condition of traffic flow is prominent,and the average speed dispersion is very obvious.Aiming at the difference between the ring expressway and the ordinary expressway,this paper analyzed the average speed dispersion in the process of traffic flow,established the traffic flow mechanics model of the ring expressway based on the average speed dispersion,and analyzed the relationship between the average speed dispersion and the traffic flow.At the same time,the influence of lane change behavior on traffic capacity was analyzed,the existing lane change model was improved,and the capacity model of ring expressway was established.The main research work of this paper includes:Firstly,from a macro perspective,the differences among the ring expressway,the urban expressway and ordinary expressway were analyzed,the characteristics that many ramps are at the entrance and exit of the ring expressway,the spacing is small,and the average speed dispersion are mainly cars were highlighted.Then the characteristics of the traffic flow in each traffic area of the freeway were summarized,the characteristics and mechanism of the discrete phenomenon of the freeway speed were analyzed,the influencing factors of the discrete phenomenon were analyzed,at the end it was concluded that the frequent lane change is the important cause of the discrete phenomenon of the ring freeway.Secondly,the relationship between the discrete degree of speed and the traffic flow parameters was explored,the intrinsic relations between the average speed dispersion and traffic flow parameters "flow,speed,density " were analyzed in different traffic flow condition,the multiple lanes of traffic flow dynamic model was built based on the front car information and lane changing rules,which was calibrated with the measured data.Thirdly,the changes of traffic capacity in each lane of the main line under the influence of ramp traffic and the influence of ramp traffic on the discrete speed of the main line were analyzed.Then,the hypothesis of the Laval.J.A four-parameter model was improved,and the improved model was used to construct the frequent lane change capacity model.Finally,the microscopic simulation research for the survey area was done with the VISSIM simulation software,the microscopic simulation capacity value of the confluence area was got,and combining with the measured data,the sensitivity analysis of simulation design parameter was done,then simulation model parameters were calibrated to determine the data files of the traffic capacity of confluence area,compare and analysis of the differences between the simulation value and the measured data.Based on the ratio of frequent lane-changing capacity and actual capacity,the change of frequent lane-changing capacity reduction coefficient was obtained,and the impact of frequent lane-changing on the capacity of the ring freeway was divided into favorable,unfavorable and very unfavorable after analysis.