高速公路停车视距可靠性设计

Reliability Design for Stopping Sight Distance of Expressway

针对高速公路的停车视距进行研究,在现行规范《公路路线设计规范》计算停车视距的基础上,考虑汽车实际的制动过程,将制动过程分为4个阶段:驾驶员的感觉反应阶段、制动系统的间隙消除阶段、制动力上升阶段以及完全制动阶段,改进停车视距计算模型;并引入可靠度理论,基于该模型构建视距可靠度功能函数,对"驾驶员反应时间、汽车运行速度、路面摩擦系数等"随机变量的随机性及其分布规律进行分析。采用一次二阶矩方法讨论现行规范的停车视距设计取值的安全可靠性,提出采用失效概率来描述行车视距的安全可靠性。根据《公路工程结构可靠度设计统一标准》,为满足高速公路对应安全等级的可靠度要求,计算在120,100,80 km/h共3种设计速度下的停车视距值,并结合实例验证计算结果具有较高安全性。研究结果表明:引入可靠度理论经改进后计算模型计算的停车视距值大于现行规范值,其安全可靠度也明显高于规范值,120,100,80 km/h速度下停车视距失效概率分别降低22.32%,13.2%, 18.9%;视距失效概率较大,表明视距设计不足,易引发交通事故,推行基于可靠度理论计算得到的停车视距值进行高速公路设计,可提高道路安全性。

To research the stopping sight distance of expressway,based on the method for calculating stopping sight distance in current specifications Design Specification for Highway Alignment,considering the actual vehicle braking process,the braking process is divided into 4 stages:driver’s sensory reaction stage,braking system clearance elimination stage,braking force rising stage and complete braking stage,the stopping sight distance calculation model is improved.By introducing the reliability theory,the reliability function is established based on the optimized calculation model.Then,the randomness and the distribution of random variables,including reaction time of driver,vehicle operating speed and surface friction coefficient,etc.,are analysed.The safety reliability of the designed stopping sight distance specified in current specifications is discussed with first-order second-moment method,and the failure probability is used to describe the safety reliability of driving sight distance.According to the reliability requirement of the corresponding safety classes of expressway in Unified Standard for Reliability Design of Highway Engineering Structures,the stopping sight distances at the designd speeds of 120,100,80 km/h are calculated respectively,and an example is given to verify the higher security of the calculated values.The result shows that(1)The stopping sight distance values calculated based on the reliability theory and the improved calculation model are greater than that in current specifications.The safety reliability is also obviously higher.The failure probabilities of stopping sight distance at speeds of 120,10,80 km/h are reduced by 22.32%,13.2%,18.9%respectively.(2)The higher failure probability of sight distance indicates that the design of sight distance is inadequate and it is easy to cause traffic accidents.It is possible to improve the road safety by implementing the stopping sight distance value based on the reliability theory in expressway design.