Fog Highway Traffic Safety Analysis And Research,

Since the first expressway was built in mainland of China in 1988, the construction and the traffic course of expressway has increasingly enhanced. Meanwhile, the rate of accidents occuning on expressway has also increased, while this caused by ambient fog obviously tend to ascent. The accidents caused by fog on expressway not only result in lots of injuries and deaths, but also lead to large economic loss. Consequently, it has received more attention from communications departments and press circles.The paper sums up the researches on fog and expressway visibility from domestic and abroad. According to the definition of ambient fog and its forming characteristics, conditions and features of the fog forming in the areas along some typical expressway are pointed out. With the Lambert-Beer law and the relative luminance contrast equation, course of visibility reduction and traffic safety influenced by fog is analyzed. The data of physical parameters from typical fog occuning in the areas along the Huning Expressway are used. With the statistical method, relations between the visual range in fog and these parameters, such as number density of fog droplet and moisture content in fog, are analyzed. As a result, the regression relations are obtained. In addition, the paper provides the quantitative relation between visual range and extinction coefficient. Furthermore, the change of visual range influenced by the microscopic parameters of fog is discussed. The safe velocity limited by visual range in expressway is analyzed. As an example, values of the velocity limited responding to different visual ranges in fog on Huning Expressway are calculated.The paper sums up the present situations in traffic manage to fog on expressway in China and points out the flaws. According to the managing measure to fog on expressway in abroad especially in the U.S.A., the traffic safety system is suggested. The system consists of four parts: fog prediction and surveillance system, traffic monitor system, outline indication and traffic organizing. It can be used to effectively prevent accident occurring on expressway in fog weather.Finally, as a technology of artificial fog dissipation, the feasibility of dynamic method to improve visual range in fog on expressway is discussed.