Theory And Methods Of Traffic Safety Security For Mountainous Freeways

During the recent years, the rapid development creates a solid transportation infrastructure for rural areas in China, particularly with the construction of a large number of high grade freeways in mountainous regions. Under the help and guide of these facilities, the life mode has been changed and its quality has been improved as well due to the free freeway traffic. However, one issue should not be ignored which is just the traffic accidents and severities. By far, such a concern and its related problems have evolved into a heated topic. Therefore, it is urgently required to carry out the research on traffic safety security theory, methods and techniques.This research has collected5426accident samples over the years of2005～2008from three typical mountainous freeways in China:North Yue Section of Jingzhu Freeway, Chongqing Section of Chengyu Freeway and Shenda Freeway. Following the analysis of distribution features of traffic accident in mountainous areas, this research has made a deep insight into the safety security theory and methods for mountainous freeway traffic, which aims to provide some valuable technique support for the freeway design and operation management in mountainous areas, and the achievements of this research also helps improve the overall safety level of mountainous freeways in China.The effect factors are defined firstly and the relationship between geometric factors including radius of horizontal curve, angle of rotation, longitudinal slope, radius of vertical curve, rotation-slope joint variable and accident rates are analyzed and the mathematical models are put forward. At the same time, the influences of drivers, motor vehicles and environmental condition on the occurrence likelihood of accidents on mountainous freeway are compared with those on plain areas.On the basis of analyzing the present identification methods of road black spot, the corresponding black detection and treatment techniques are discussed. Considering the geometric condition of black spot locations and traffic flows, the FCM clustering method is proposed to identify the black spots in mountainous areas. Combining the accident observations from North Yue Section of Jingzhu Freeway, the causes of the original13black spots are analyzed and the18effect factors are clustered into4types according to the level of effect. Then the safety improvement measures are proposed to treat with the segments consisting curves, up and down grade and cross sections.Re-considering the roadside accident data, the characteristics of roadside crashes in mountainous freeway is analyzed and compared the research differences of roadside safety space and roadside barriers between China and USA. The evaluation level is divided and then the safety measures are provided for roadside safety including facilities improvement, management suggestions and barrier disposal operations. Due to the driving vision distance, roadside safety design method is proposed considering the driver’s vision, which ensures the safety of road-side design from the horizon and vertical angles.After analyzing the relation between environment condition, especially the snow, rain, fog and other adverse weather factors, and traffic safety, the concept of visibility is introduced to construct the speed limit model using the safe following distance equation between the guiding-following vehicles. Therefore, the speed limit standards are determined for different visibilities under the condition of fog, rain and snow day. The risk driving behaviors are clustered and6penalties standards are provided for the three types of risk driving behaviors that prone to cause accident, induce traffic conflicts and affect the traffic efficiency.In this paper, the corresponding theory and methods for traffic safety security of mountainous freeways is treated with as the breakthrough point and it recommends a breakthrough in four fields:①suggesting the roadside safety improvement measures for mountainous freeway;②proposing the roadside safety design method considering the driver’s vision scale;③constructing the speed limit standards for mountainous freeways under extrem weather conditions;④providing the penalties measures and standards for risk driving behaviors on mountainous freeways. Given the imperfections of this study, and the limitation of this theoretical models and methods, the improvement of this research and construction of simulation program and demonstration project merits further deep researches.