Study On Safety Of Flat And Longitudinal Alignment Combination Of Expressway In Zhejiang Province

The combination design of horizontal and vertical alignment is one of the most important links in the alignment design of expressway.The combination of horizontal and vertical alignment directly affects the safety of the corresponding sections.Therefore,the study of the safety of the combination of horizontal and vertical alignment has important practical significance for the alignment safety design of expressways in Zhejiang Province and even the whole country.On the basis of collecting the data of horizontal and vertical alignment design of expressways in service in Zhejiang Province and five-year traffic accident history data,this paper qualitatively analyses the design principles of horizontal and vertical alignment combination from three aspects: continuity and comfort of horizontal and vertical alignment combination,balance of horizontal and vertical alignment index and appropriate synthetic gradient.The advantages and disadvantages of different spatial alignment elements combination are analyzed by perspective theory.The accident mechanism of poor alignment of horizontal and vertical alignment is qualitatively analyzed from the aspects of alignment coordination,visual continuity and rationality of synthetic gradient.Using homogeneity method,the highway alignment is divided into the smallest unit module,and the accident rate is taken as the safety evaluation index.The discrete distribution degree of different types of horizontal and vertical alignment combination traffic accidents is studied,and the horizontal and vertical alignment combination forms are determined.The relationship between radius ratio,gradient difference and relative position of changing slope points and traffic safety in the combination of horizontal and vertical alignment is studied,and the combination of horizontal and vertical alignment indexes satisfying safety expectation is put forward.The grey clustering method is used to evaluate the safety of each horizontal and vertical alignment combination section,and the discriminant model of the relationship between the horizontal and vertical alignment combination section and traffic safety is established.According to the different severity of highway accident,the method of distinguishing the safety of different linear combination is given.With the help of the research results of the relationship between horizontal and vertical alignment combination and traffic safety,this paper puts forward the safety improvement safeguard measures of the bad horizontal and vertical alignment combination section after discrimination,mainly including speed control,marking,visual improvement,roadside guardrail protection grade enhancement,road surface Comprehensive Drainage and so on,which provides a certain reference for the safety design and safety guarantee of expressway.