Study On The Impact Mechanism Of Large Vehicle On Traffic Safety About Freeway Upgrade Section And The Research Of Improvement

Due to the limit of terrain, landforms and geology, some freeway sections are consisted of long and steep slope in order to adapting to the terrain, reducing damage to the environment and landscape, reducing the project cost, which are often freeway traffic accident black-spots. With the increasing demand of the transportation and the development of city, the construction of highway and the rapid development of the logistics industry enables the rapid development of large transport vehicles which are larger and heavier. Then, the adverse effects of the large vehicles on the traffic flow and safety of freeway upgrade section will be more prominent.Through the collection of lots of reference, the existing research on the status of the impacts of the large vehicles on traffic flow and the relationship between the traffic flow and safety is classified. Comprehensively considering time, labor power and safety factors, a detailed survey programis developed. Through observing East Lushan segment of Nanjing-Hangzhou Freeway, the data is collected such as road design parameters, traffic volume, traffic composition and speed of different vehicles. At the same time, on the basis of the basic features of large vehicles and the moving bottleneck under different service levels, the article analyzes the characteristics of freeway upgrade section.Due to the constraints of objective conditions, traffic flow characteristics on upgrade are studied based on the micro-simulation software VISSIM. The calibration and validation of simulation model are done by using observed data, speed standard deviation coefficient (Cv) and average changing times between car and large vehicle, the index representing the impact of large vehicles on freeway upgrade section, are analyzed in different traffic and road conditions by a series of simulation tests on upgrade section with straight road section before and after. This paper analyzes the relationship between Cv and the rate of accident, using the cumulative frequency of the rate of accident. Then this paper determines the safety evaluation criteria based on Cv that can analyze the impact of large vehicles on freeway upgrade section.Finally, this paper puts forward measures to improve safety including engineering measures and traffic management measures to manage the traffic flow effectively so that we can reduce the accidents and ensure the safety of freeway upgrade section...