Research On Speed Limit Of Mountain Highway Under The Influence Of Adverse Weather

In 2018,the newly-opened expressway of China’s expressways was about 6,000 kilometers,and the total mileage of expressways has exceeded 140,000 kilometers,this number far exceeds any other country in the world.With the rapid development of China’s economy,people’s demand for expressway is also increasing.Although the absolute number of traffic accidents on mountainous highway is not obviously more than that in other areas,the accident severity and fatality rate are higher than those on plain highway,and the major traffic accidents account for more than 60% of the country.At the same time,adverse weather conditions have further deteriorated the traffic environment of mountainous highways.Not only affects the expressway capacity,but also increases the traffic accident rate and the severity of the accident.According to statistics from authoritative departments,the traffic congestion caused by highways(rain,snow,fog)directly accounts for 15%.Therefore,this paper studies the characteristics of highway accidents and speed limit in bad weather conditions,and provides theoretical basis and technical support for improving the traffic safety of highways under bad weather conditions.Firstly,the influencing factors and characteristics of traffic accidents of expressways in mountainous areas are sorted out and analyzed.Based on a large number of relevant research results at home and abroad,the concept of bad weather and highway speed indicators is defined,and qualitative analysis of the influencing factors of highway traffic accidents is carried out from the perspectives of people,vehicles,roads and environment,which provides a theoretical basis for further research.Secondly,through the quantitative analysis of the traffic accident data of Luoluan Expressway 2013-2017,the influence degree of bad weather and road conditions of accident location on the number and severity of traffic accidents on Luoluan Expressway is studied.Then,the multivariate analysis of variance is applied to the characteristics of the correlation analysis of qualitative variables.It is confirmed that the influence of weather factors on the severity of traffic accidents is significant.In the aspect of speed limit,by analyzing and comparing the advantages and disadvantages of the existing vehicle following model,a speed limit model based on the safety spacing model and considering the driver characteristics is established.Based on this,the safe travel distance between the bad weather and the vehicle is further discussed.According to the model,the proposed method for determining the speed limit value under fog,rain and snow weather conditions is discussed.The speed limit values of factors such as road adhesion coefficient,driver response time and road longitudinal slope are obtained respectively.Finally,the simulation results of the speed limit calculation result are verified by using CarSim software.The results show that the speed limit calculated in this paper can ensure the safety of driving and the speed limit of the ordinary highway section under the bad weather conditions should be lower than the road design speed limit.This paper proposes the speed limit value to guarantee the highway traffic under bad weather conditions.Safety has practical reference significance.