Study On Operating Speed Prediction Models For Small Vehicles On Combined Sharp Horizontal And Vital Curves On Mountainous Expressway

Among the plains,hills and mountains,the number of accidents in the mountain highway is the least,but the death toll and the direct property loss per hundred accidents are the most.Therefore,it is necessary to make a thorough study of the expressway in the mountain area.The appropriate degree of road alignment design is found to be significantly associated with traffic accidents.Therefore,negative alignment combinations are the main factors to be considered in safety evaluation of road design.The operating speed,as the result of the joint effects of the driving behavior,physical and mental statuses of the driver,visual demand,vehicle performance characteristics,linear geometric elements and other factors,is an important reference standard for safety evaluation of road alignment.In this paper,the operating speed of small vehicles on combined sharp horizontal and vital curves on Henan Province,Luoyang-Luanchuan expressway is studied to establish accurate prediction models of operating speed effectively,which are conducive to the alignment selection in expressway design,the safety evaluation of the built expressway alignment and the improvement of bad linear conditions.On the basis of road alignment indices,the relationship between operating speed and the factors including horizontal alignment,vertical alignment,cross section of linear and linear combination is analyzed in this paper.The characteristic point speed observation test is carried out on combined sharp horizontal and vital curves,and the operating speed of the characteristic points are calculated.And then,the characteristics of operating speed on combined sharp horizontal and vital curves are analyzed.The road alignment factors are selected by partial correlation analysis and factor collinearity diagnosis to determine the variables of multivariate linear regression model.Combine with the elected variables,operating speed prediction models for small vehicles on midpoint of curve of combined sharp horizontal and vital curves are established in the condition of straight-curve inlet and curve-curve inlet and operating speed prediction models for small vehicles on terminal of curve of combined sharp horizontal and vital curves are established in the condition of curve-straight exit and curve-curve exit.Then,4 models established are tested by the statistical method and the validity of the models is confirmed.According to the analysis of influence factors for the operating speed,the input and output variables and the corresponding membership function of fuzzy inference speed prediction model are ensured.The input variables include radius of horizontal curve,first half slope,second half slope,exit radius,inlet velocity;the output variables include middle speed,outlet speed.Then,in view of the application of fuzzy inference theory,operating speed prediction model for small vehicles on combined sharp horizontal and vital curves on mountainous expressway is established.Finally,the regression model and the fuzzy inference model are verified by the measured data.The results show that the two models can be used to predict the operating speed of small vehicles on combined sharp horizontal and vital curves on mountainous expressway is established.