Research On The Mainline Indicator Of Interchange

The integral security and economy of interchange are concerned on the rationalization ofmain line alignment, especially the technical indicator of main line. Although the correlatedtechnical indicators of main line are demanded in the Design Specification for HighwayAlignment, its value that rarely be researched do not have detailed description. The mainlineindicator value is random selected by the designer. The alignment is not reasonable and cannot meet the requirement of vehicle safe and engineering economy. Therefore the study ofmainline indicator is a problem that needs for solved.The limited factors of mainline horizontal and vertical technical indicator are proposedby collected a large number of relational data. It contains the safety and comfort of vehicle,the identified sight distance and the interchange integrality. The value of identified sightdistance is computed by analyzed the process, which the drivers identify the diverging pointmarking of deceleration lane and change lane. According to identified sight distance, theradius of horizontal and vertical curve is obtained by the geometrical computed model. Finally,according to the influence between grade and acceleration, the operated speed is computed bythe length computed model on the diverging point and merging point with the different grades.And compared it with the safe operated speed, the value of grade is recommended on thescope of interchange.The research conclusions provide a theoretical basis to the value of horizontal andvertical indicators and it has practical significance.