Research On Trumpet Interchange Appropriate Size

The freeway network in China gradually forming, the cross between the highway willlead to a large quantity building of interchange. But some interchange pursuit in large scale,high speed index, Smoothly design line, which leads to the interchange project investment toolarge. Due to China’s large population base, the limited environmental capacity, it requiresChina’s economy transformation from bold type to fine type, which puts forward newrequirements of novation for interchange designers. How to reduce interchange scaleeffectively, and how to meet the future traffic demand, is an important problem in this thesis.In this article, we aim at trumpet shaped interchange as the research object, using thearea represent the interchange scale. We analyses the influence factors of interchange scale,including the interchange location, angle between road and main line, ramp circular curveradius, and the design of super-elevation between, design speed and circular curve radius.And we focus on the analysis of the influence of interchange ramp circular curve radius scaleand then we establish a calculation model of circular curve radius and inner ramp area.The design of interchange ramp must meet the expectations of the traffic capacity andservice level. By considering traffic engineering factors, analysis of highway traffic flowcharacteristics, the level of service capacity, we get different interchange scales in differentservice levels and capacity.We make the service level classification in reference to《Design Specification forHighway Alignment》, using traffic flow density as the evaluation index, and then we analythe Longmen interchange project large-scale, medium-scale and small-scale. And in order tomeet the target service level, we use the VISSIM microscopic traffic simulation software tosimulate the middle ramp section and the confluence area of the traffic flow simulation, verifythe feasibility of small scale interchange.In this article, we make connection between the scale and level of service of trumpetinterchange. Designers can reasonably select ramp alignment index, control of overpass scale,according to the forecast of traffic volume, specify the target service level. Especially inlimited mountainous area, it is full of vital significance.