Study On The Minimum Spacing Of Interchanges On Freeway

Interchange is an important part of the freeway,which plays the role of traffic transformation,grooming and controlling between freeway and the freeway or freeway and trunk.It is of significant influence to the traffic attraction and distribution,transportation and distribution of materials of the surrounding areas,it also has a far-reaching significance on promoting regional economic development and the improvement of living standard of the people.However,due to the economic development of the region,the national freeway network and local road network staggered arrangement.In order to achieve the conversion of traffic flow,we must set interchange.It is easy to occur"Interchange group"at close range, which will lead to road congestion and traffic,so interchange regional is the bottleneck of the whole freeway system.In order to improving the capacity,operational efficiency,security of the region,this article seeks to study of minimum spacing of freeway interchanges from both the macro-traffic and micro-traffic flow theory and the micro of it.This article first defines freeway interchange spacing and analyses the factors that influence it,including traffic density,sub-merging and weaving area characteristics of the traffic flow,traffic signs and signals of the layout,the driver's comfort,economic factors and environmental landscape,etc.Then by collecting designed information of more than hundreds of interchanges,fully considered the design time and geographical differences,statistically analyzing the structure length of the interchanges in our country,compared with the models, at last determined the minimum structure length of different interchange.For two independent adjacent interchanges,the minimum interchange spacing is determined based on the physical characteristics of the road users,driving comfort and road traffic conditions,considering the most disadvantaged driving manner to determined the minimum separation by use of lane-changing theory.The determination of that two adjacent interchanges linked by auxiliary Lanes which was determined.First,by use of the method of analysis weaving areas in"Highway capacity manual"of China,look on traffic density as the main indicators of efficiency to evaluate the operating quality,make weaving length meeting the target service levels(second class level of service)as a controlling condition to determine the minimum length of auxiliary lane;Then base on traffic conflict technology,make micro-traffic simulation software VISSIM as modeling tools,analysis the minimum length of the auxiliary lane meeting the target level of security(more secure)based on evaluation of the selected indicators and the establishment of evaluation system.Finally compared the most disadvantaged condition that meeting the object service and security level as the minimum length of auxiliary lane,and then determined the minimum interchanges spacingThe research of the paper provides strong theoretical guidance and reference for systematically solving traffic problem of the region of interchanges,and also offers some new methods and ideas to the existing specification relating to interchanges spacing,which has significance to some extent.