Study On Capacity Of Interchange

At present, there is not a uniform definition about interchange capacity at home and abroad, neither the capacity calculation method. The most often used capacity calculating method by domestic engineers is the"adding up method", that's take the sum of capacity of each mainline and ramp as interchange capacity to guide the interchange planning and design. But it has been proved that this capacity calculating method has certain shortcomings, such as disproportional distribution of interchange capacity among all the interchange compositions. In our opinion, the radical reason of this phenomenon is: the above method doesn't consider the differences of traffic demand among different traffic flow directions of interchange.In light of the existing problems and causes of"adding up method", the author put forwards the concepts of design capacity and actual capacity, together with the point that interchange capacity should be one to one correspondent with the level of service (LOS). In details, design capacity under a certain LOS is the sum of each mainline and ramp capacity, actual capacity under a certain LOS is the total volume that can be accommodated by interchange under the design flow direction and volume, while one of the interchange compositions has reached the above LOS.Chapter 2 of this paper has generalized and analyzed the production in interchange capacity field at home and abroad. Chapter 3 has put forward a new set of theory to calculate the capacity of each composition of interchange, including weaving segment, mainline segment in merge (diverge) area, ramp junction, and basic segment of mainline and ramp. Chapter 4 has given out the definition and calculating method of interchange capacity. Finally, chapter 5 takes example of Gonghe interchange in Shanghai to illuminate the differences between design capacity and actual capacity, to show how to carry through operation analysis and make correspondent improvements with the new theory in this paper.