Evaluation Of Highway Geometric Design Three-Dimensional Alignment

Highway is a three-dimensional space banded structure.Highway geometric design is a representation of the geometry of the three-dimensional belt,which is very important to improve the operation quality and guarantee the safety performance of highway.Iterative design process should be integrated into the highway design process.The demands of different design stages have a great effect on geometric design alignments.In this paper,highway performance is defined as vehicle operation time,vehicle operation energy consumption and highway safety performance,which are influenced by geometric design alignments.Highway engineering design stage is the elaboration of the preliminary design.In view of the present design stage only takes the route length and project cost as the selection standard of the route scheme comparison,not considering highway performance.Therefore,this paper introduced the vehicle path planning and driving safety risk prediction of the design phase to redefine and forecast in quantity,and to meet the demand of highway geometric design optimization in the design stage which is not affected by the dynamic traffic volume.By studying the relationship of geometric design decision and highway performance in the preliminary design and the design phase,this paper put forward the iterative design method should be integrated into the whole process of highway design.By analyzing the relationship between vehicle path planning and highway geometric design,the three-dimensional road surface model was established by using differential geometry theory and vehicle path planning in the 3D space.And it was applied to the establishment of the evaluation model of highway performance,such as vehicle operation time,vehicle operation energy consumption and highway safety performance.It provides a standard for quantitative comparison of optimal three-dimensional alignment in highway geometric design.Vehicle speed profile is planned with the three-dimensional design index geodesic curvature6)₂),and the vehicle operation time evaluation model is obtained.For the existing three-dimensional road surface approximation model and particle vehicle model,a wheel model based on the three-dimensional road surface analytical model was proposed,and the vehicle energy consumption evaluation model was obtained.Based on the theory of near-crashes this paper defined driving safety risk,and presented a description method of the relation between lateral acceleration,longitudinal acceleration and speed.Highway geometric design three-dimensional alignment safety performance evaluation model based on driving safety risk prediction is established.Through a section of Sichuan province highway of final design scheme comparison,highway performance indicators should also be introduced.This paper established the evaluation model of vehicle operation time,vehicle operation energy consumption and highway safety performance.It provides a quantitative comparison method for the optimization of the highway alignment design in the whole life cycle.Moreover,it also provided a new research method for vehicle operation and highway safety analysis with the three-dimensional road surface model and the wheel model.