Design Method For Improving The Safety Of Low Grade Highway In Mountain Area

With the rapid development of economy in our country, the traffic network construction increase rapidly, especially for the growing of highway construction, which gradually reach to the saturation level. At the same time, the low grade road(Fourth class roads and substandard roads) which located at the bottom of road class faces good developing opportunities. The ministry of communications makes a demand of safety, environmental protection, and sustainable development for road design. It requires to achieve the goal of people-oriented, safety first, environmental protection, natural harmony, resource saving and sustainable development during the design process. How better to construct harmonious road is a big issue now.The function of low grade of highway in mountainous regions is mainly to serve for the people at mountainous areas. When doing the design of highway in mountainous regions, it should mainly focus on the safety issue and the particular condition of mountainous area, and it should do the targeted design based on the different terrain condition, which to avoid norms or standard copying phenomenon. It needs to consider from the actual situation in the design to ensure the quality of the engineering. Due to the influence of geological environment, the route is poor, which is prone to accidents.The plane and vertical indexes of geometrical linear design is particularly important when doing engineering design. However, it uses design speed to direct the design in the traditional design, it means when the design speed is determined the other related technical indexes is limited in a certain range, and then doing the design according to the actual topography condition. But the drivers will not drive at the design speed range, the driving speed will be different under the comprehensive condition, and it will exceed the design speed at some parts of the road, which means the driving speed and design speed have a large difference. The driving speed is introduced in the study, and the concept of driving speed and character is analyzed and expounded. Through vehicle driving rules studying and data analysis, the driving speed calculating model of low grade highways in mountainous regions is established on the basic of domestic running speed calculating model. A set of suitable design method for low grade highways in mountainous regions is concluded according to the design route safety evaluation by safety evaluation system and linear indicator adjustment and optimization of the route with safety risks.