Study On The Minimum Length Of Weaving Area Of Expressway Interchange Ramp Section

At present,in the interchange area,due to land use or cost restrictions,there is a ramp road section sharing a road and forming a ramp road section interweaving area.However,the current route specifications and interchange design rules in China do not clearly stipulate the value of the length of the interweaving zone when there is an interweaving zone on the ramp section,so designers often determine the length of the interweaving zone based on experience.The interweaving area of the ramp section will be more congested.Therefore,it is necessary to study the minimum length value of weaving area in the ramp section to help designers have the reference of the minimum length value in the design process.First of all,the paper introduces the definition of the ramp section interweaving zone on the basis of carefully studying the existing research results of the interweaving zone,and analyzes the factors affecting the traffic operation of the ramp section interweaving zone.Secondly,it analyzes the following behavior,lane changing behavior and lateral behavior of vehicles running in the interweaving area of the ramp section.And based on the theory of acceptable gaps,amends the software’s lane changing model parameters.Based on the Wiedemann physiologicalpsychological following model The parameters of the car-following model were revised,and the traffic flow in the interweaving area of the ramp section was studied by analyzing and using the Wiedemann physiological-psychological car-following model,the gap acceptance theory to analyze the lane change model,and the vehicle speed and slope relationship model.Then,for50 km / h,40 km / h,35 km / h,and 30 km / h ramp road interweaving zones,VISSIM software was used to build models of ramp road segments of different lengths,and the corresponding fourlevel service level was designed according to different design speeds..Based on the analysis of the traffic flow characteristics of vehicles in the area of the intersection of highway interchange ramps and the relationship between the three parameters of traffic flow,the relationship between the average density of traffic and the length of the interweaving zone of the ramp section is established.After summarizing,determine the length of the interweaving zone at a given slope condition.Then change the slope of the longitudinal slope of the interweaving area,and use the same method to obtain the recommended length of the interweaving area of the ramp section under different longitudinal slope conditions.Next,the relationship between the longitudinal slope and the length of the interweaving area is analyzed,and the recommended value of the minimum length of the interweaving area of the ramp section under the design speed and longitudinal slope is given.In the same way,the recommended value of the minimum length of the interweaving zone of different longitudinal ramp road sections at different design speeds can also be obtained.Finally,through the simulation of engineering examples,the rationality of the minimum length of the interweaving zone of the ramp section proposed in the paper is further verified.It is pointed out that the length of weaving segment is affected by the longitudinal slope.The reference values of minimum length of weaving segment of ramp section under different longitudinal slope conditions with design speed of 30km/h,35km/h,40km/h and 50km/h are established respectively.On this basis,it is proposed that the longitudinal gradient of the section with weaving zone on the ramp with design speed of 40km/h and 50km/h should not be greater than or equal to 6% and 5%.To help designers in the design of the weaving area of the ramp section to provide a reference,so that the ramp section can ensure its traffic efficiency.