Research On Sight Distance Calculation And Safety Evaluation Method For High-grade Highway Curves

The sight distance of curved roads is an important factor that affects the safety of high-grade highways.The sight distance evaluation is also an important content in the safety evaluation of highway projects.Sight distance safety is affected by many factors including people,cars,roads,and the environment,and there are also interactions among these factors.Existing sight distance calculation methods often only take into account the effects of limited factors when performing safety assessments,do not take the overall traffic environment into account in all directions,and the evaluation process is not standardized.In view of this problem,this paper studies the method of sight distance measurement and safety evaluation of high-grade highway curves.The thesis starts with the parking sight distance as a safety criterion and analyzes the relationship among ground friction and lateral braking force and longitudinal braking force based on the "circle conditions" of corner braking.The high circular curve and the curved slope combined road section analyze the force of the vehicle,explore the speed and acceleration changes under the lateral stability conditions of the vehicle on these three roads,and derive the expression of the braking distance;The calculation model for the parking sight distance of curved is given,and the applicable conditions of the model are given.Then,the geometrical sight distance of the highway design stage is analyzed from three perspectives: plane sight distance,longitudinal sight distance and spatial sight distance.Aiming at the plane sight distance,the relationship between the plane sight distance and the horizontal and vertical distance of the highway is elaborated.Based on the calculation of the maximum horizontal and clear distance when the transition curve is set,the original calculation expressions for the widened sections are modified;In terms of longitudinal sight distance,the problems of convex vertical and concave vertical-curve sections were proposed,and their minimum length and minimum radius were controlled.In terms of spatial sight distance,the coordination Principles related to sight distance of linear combinations was elaborated,and list some disadvantageous combinations that should be avoided.Then,in view of the actual sight distance measurement in the highway operation phase,a new idea based on machine vision and lane extraction was proposed.Based on the RGBimages of the Bicheng Expressway collected in the field,it was grayed out and enhanced using Matlab software;the images were binarized by threshold segmentation,and the outer lane lines were detected by Huff transform based on edge detection;Taking the outer lane line as a reference,the intermittent scanning lane line is extracted by the following scanning method,and the algorithm is designed to achieve the actual sight distance calculation of the highway.Finally,based on the above research results,a process for sight distance safety evaluation during the design and operation phases of the highway is established with examples,and related engineering measures to improve sight distance are summarized.Compared with the existing sight distance calculation and safety evaluation methods,this paper considers the comprehensive influence of various factors in the traffic environment,and provides new ideas and methods for the reliability of highway sight distance calculation and the standardization of the evaluation process.