The Evaluation Method Of Expressway Alignment Adaptability Based On Operating Speed

Expressway should be well adaptive for vehicles operation safety, comfortable,consistency in alignment design, it is that the extent to alignment should be better;the alignment adaptability can be made of consistency; safety; comfortableness tocomprehensive presentation. while how to evaluate the extent of expresswayalignment, the research in this area is very little in domestic and foreign currently,they often made a single analysis on alignment safety or comfortableness, andlacked a evaluation research as whole, in a single analysis of research often can’timprove on expressway alignment comprehensively; Therefore, from the Angle ofthe adaptability to evaluate the quality of the alignment is very necessary.The operating speed of vehicle is the comprehensive effect of alignment index,which is related to driving safety, comfort, continuity closely, then build acomprehensive evaluation model of alignment adaptability with speed as thefoundation. The foundation of the evaluation is the speed prediction research,considering the speed of different alignment conditions will keep changing, thepaper put forward the velocity variable prediction model, made the speed ofprediction research more reasonable;The first, this paper analyzed the investigation of the road alignment, reachedeach section of the alignment indicator; and then analyzed the investigation of theroad traffic flow, this paper briefly introduces the survey method and the dataextraction process, determined the small and large vehicles as the research object,use the technology to make it satisfy the free flow state; and obtained the V85valuespeed indicator with statistical method, to lay the foundation for the building of thevelocity variable prediction model.Secondly, according to the vertical alignment, using the two indexes of slopeand slope length, established the relation model of the uphill and the downhill’smileage slope with velocity variable; according to the horizontal alignment,analyzed the curvature change rate of the comprehensive index CCRS; establishedthe relation model of the first half and the second half’s curvature change rate withvelocity variable; then analyzed the combination of alignment’s velocity variableprediction, got a conclusion that the combination of alignment’s speed predictingmethod, and draw the related calculation flow chart.Next, based on the velocity variable and the speed, determined the85%of the velocity difference, lateral acceleration, axial acceleration, variation coefficient,unit mileage of speed relative difference as evaluation indexes. according to eachindex and operating speed relationship model, used the principal componentanalytical method, established the comprehensive evaluation model, and regardedthe coefficient of adaptability as the standard.Finally, selected one of the sections of beijing-zhuhai expressway as the caseanalysis, based on the velocity variable prediction, used the comprehensiveevaluation model and calculated each section’s coefficient of adaptability, accordingto the evaluation standard, obtained the poor sections, the model is proved thefeasibility of application, provided a certain theoretical basis for the improvementof expressway alignment.