Three-dimensional Space Description Model of Geometric Alignment Comprehensive Index of Highway

In order to evaluate the objective safety of road alignment synthetically,according to the influence of the space geometric characteristic index of the horizontal,vertical and cross-sectional alignment index on speed and safety and considering the driving behavior,the horizontal,vertical and cross-sectional alignment comprehensive index functions are set.Based on the space geometric theory and the alignment design characteristics,the three-dimensional road alignment comprehensive index description models including curvature,curvature variation,the angle of curve,grade and lane width are established by using the mode of horizontal,vertical index as primary and the cross-sectional index as correction.At the same time,the influence of the bridge and the tunnel are also considered.Three-dimensional space description modeling of alignment comprehensive index solves the key technical problem of operating speed prediction and alignment safety evaluation.