Research On Optimization Method Of Road Traffic Safety Facilities Under The Influence Of Visibility

Visibility is a critical factor affecting traffic safety.Reduced visibility will directly affect the driver's perception on road geometric alignment and characteristics of the traffic flow,and thus easily cause accidents.As an essential infrastructure in municipal engineering,the construction of road traffic safety facility directly affects personal safety of traffic participant and efficient operation of road traffic system.However,most of the existing studies on road traffic safety facility mainly focus on the good weather conditions and seldom consider the impacts of environmental factors such as visibility.This will lead to the existing road traffic safety facilities can not give fully play to the function of ensuring traffic safety and reducing the severity of accidents under low-visibility conditions.Thus,exploring the optimization method of road traffic safety facility under the influence of visibility is of great theoretical and practical significance,which is helpful to maximize the effectiveness of road trafic safety facility and ensure the safety of drivers under low-visibility conditions.Based on the National Natural Science Fund Project "Accident Risk Assessment of Highway Traffic Flow and Optimization of Safety Design Parameters under the Influence of Visibility",the research explores the optimization method of road traffic safety facility under the influence of visibility systematically.The main work of this dissertation is composed of five sections as follows:Firstly,based on valid traffic accidents records under low-visibility conditions,the occurrence or absence of a low-visibility fatal accident was set as the dependent variable.The more important influence factors that screened by the variables importance sorting method of random forest were set as independent factors.And then,a binomial logistic model was developed based on these factors to evaluate the impacts of independent factors on the severity of these accidents.The results show that visibility,accident modality,presence of a median divider,road surface conditions,accident site and road type are important factors that affect the severity of traffic accidents under low visibility conditions.Secondly,a driving simulator experiment was conducted to collect drivers'micro-driving behavior data under different visibility conditions and road alignment conditions.Anova was used to explore the differences in micro-driving behaviors of drivers under different visibility and road alignment conditions.A fine classification method of road traffic visibility was proposed.The results show that average speed is significantly different under different visibility conditions.A specific classification of road traffic visibility of straight section and curved section has been proposed on this basis.Thirdly,to determine reasonable driving speed limit in dynamic low visibility environment,driving simulator experimental research on drivers' visual ability affected by driving speed and visibility was conducted.The quantitative model of drivers'recognition time,driving speed and visibility was established to explain the interactive relationship among these factors in-depth.And then the determination method of reasonable driving speed in dynamic low visibility environment was given based on response-braking stopping sight distance model.By taking secondary highway as the research object,the reasonable driving speed calculation models of straight section with a certain stopping line-distance and curved section with a certain circular curve radius were constructed.And the reasonable speed limits of straight section and curved section of secondary highway under the influence of visibility were obtained.Fourthly,the game theory was used to analyze the game phenomenon existed in the setting of road traffic safety facility under low-visibility condition.By taking speed measurement system as the research object,the selection process of mixed strategy game existed in traffic management department and driver was analyzed,and the mixed strategy nash equilibrium system was established.The nash mean value of mixed strategy of game model was solved by designing the decision-making utility survey method of driver and traffic management department.And then,the setting condition of speed measurement system under low-visibility conditions was proposed.The forward prospect and backward derivation strategy were used to analyze the planning and design of road traffic safety facility under low-visibility conditions from the micro level,and the research framework solving the optimization problem of road traffic safety facility under low-visibility conditions by using the game theory was proposed.Finally,the warning road pavement was taken as the research object,and driving simulator experiment was conducted to collect the driving behavior and physiological characteristic data at road black-spots with different warning road pavements.According to different road black-spots,drivers' driving behaviors and physiological characteristics under different visibility conditions and warning road pavements were compared.The results showed that there were significant differences in driving behaviors and physiological characteristics of drivers under different visibility conditions and warning road pavements.Combined with the strategy of "forward prospect and backward derivation",the grey premium evaluation method was applied to evaluate the effectiveness of different setting methods of warning road pavement at road black-spots with the influence of visibility.Finally,the setting method of the warning road pavement under visibility condition and road black-spot coupled condition was proposed.