Research On The Method Of Setting Speed Limits On Mountainous Second-class Highway

At present,the traffic accident rate of second-class highway is much higher than other grades highway in china.The mountainous second-class highway is restricted by the mountain topography and other factors,and the traffic accident rate is more prominent.There are many factors that lead to the traffic accident of second-class highway,and the unreasonable vehicle speed is a very important factor.The previous research showed that the unreasonable driving speed would cause instable traffic flow,increase the probability of collision between vehicles,cause various types of road traffic accidents.So,reasonable control of vehicle speed through scientific speed limit is an important measure to improve the traffic safety of mountainous second-class highway.Therefore,to research the method of setting speed limits on mountainous second-class highway,and establish an objective and reasonable speed limit model and method of mountainous second-class highway are extremely urgent for preventing and improving the safety of mountainous second-class highway.Firstly,the classification threshold of curve radius and longitudinal slope were determined by analyzing the concept and the linear characteristics of mountainous second-class highway.Meanwhile,the relationship among the operation speed,traffic accident rate and severity was analyzed,and the necessity of speed limit of mountainous second-class highway was proposed from the perspective of road safety.Secondly,based on the geometric alignment of road,the index system of speed limit for mountainous second-class highway was constructed by existing research and correlation analysis between various speed limit index and operation speed.At the same time,the speed limit model of linear segment,horizontal curve segment,longitudinal slope segment and horizontal curve that combined with longitudinal slope segment of mountainous second-class highway,which were constructed by analyzing the influence of single or multiple speed limit indicator that acting on operation speed.Then,the segmentation speed limit was proposed as a method of speed limit on mountainous second-class highway by analyzing actual driving conditions.And based on the existing relevant norms,the achievements of speed limit theories,and the investigation and analysis of actual road,this paper determined the threshold of setting transition segment,minimum length of speed limit segment and the transition segment of mountainous second-class highway.Meanwhile,the speed limit road was reasonably divided by using the method of ordered cluster analysis,and the speed limit steps was provided for mountainous second-class highway.Lastly,taking measured data form NanFu road as example,this paper used the proposed speed limiting value model and the speed limiting method to analyze.And the analysis result shows that the speed limit model and method of mountainous second-class highway have certain practicality for mountainous second-class highway.Mountainous second-class highway was considered as a studying object in this paper,and a novel speed limit method was introduced,the reasonable speed limit model was established for mountainous second-class highway.This research results can provide some theories for the determination of limit value and prevention of traffic accidents of mountainous second-class highway.