The Research On Minimum Distance Between Interchanges On Urban Loop

With the accelerated process of urbanization in China, the city logistics and thepedestrian flow are aggregated in space .The conflict is getting increasingly tensebetween the traffic demand and supply .In the plan of the urban road network，theloop’s radial road network has been widely applied in the most cities in China. As thekey joint of the loop’s radial road network, the setting of interchange is animportant planning .One of the important influencing factors is a reasonable distanceof the interchange .How to study the reasonable choice of the interchange’s distance inthe urban road network from the view of the urban dynamic development has animportant role in connecting effectively the road network at all levels ,improving theoverall operation of the road network，balancing the network traffic，controlling theamount traffic of into and out of the city ,allocating reasonably the city constructionfund and designing the follow-up stage of the interchange .The research on the minimum distance of the interchange is not full in China.Only a small amount of paper has been showed . Among them most are the principle thatshould be maintained in the loop interchange’s layout, the function of the road networkbased on the characteristic of the junction,the research of the access density and the ramp form .But the majority of the study of the interchange’s distance is focused on the aspect of the highway .The results obviously don’t apply to urban road that relatively large amount of traffic,complex traffic and the evident land constraint .In this paper, with loop radial road network as the research background and theanalysis of urban traffic operational characteristics of this road network mode,meetThe service-level requirements of the urban road network, we can predict the amountof the attracted traffic interchange. As one of the most important factors to solving theminimum distance of interchange, traffic amount is introduced to the solving processin each part. A new model based on the service-levels to solving the minimum distanceof interchange is structured in this dissertation and it also supply preference for severalcommon combination of mainline ramp modes in the urban road system.Finally, with the traffic congestion phenomenon of the second belt highway in Changsha City as a pratice, this paper selects the road at three interchanges spacing asthe research object. After the accurate and reasonable investigation of the relevant data,we can calculate the several interchange spacing by using the new model, and obtainthe theoretical minimum. According to the contrast analysis with the actual distance,we can tell the reason of the traffic congestion tentatively, and give some releventrecommendations for the construction of the transformation of the second belthighway. The research results of this article have some guidance value for plnning andconstruction of the unban road network.