Research On Driver's Dynamic Visual Characteristics In Mountainous Area Highway Of Foggy Environment

In the foggy environment,the distinguishing degree of roads along with surroundings will be weakened,so that drivers would be influenced when making accurate judgment of roads ahead as well as obstacles,which will negatively affect the safe operation of expressways.There are more linear curves as well as precipitous and long longitudinal slopes of expressways in mountainous areas,which will obviously cause much more adverse effects for the safe operation,combined with fog areas.Therefore,to carry out researches of the driver's dynamic fixation feature and target dynamic identification distance on expressways of mountainous areas in foggy environment will be helpful in recognizing the characteristics of behavior choice and identification of spatial distance.Firstly,based on the basic theory of human vision and the research of the field of dynamic visual behavior during driving processes of drivers home and abroad,and combined with the driving condition of expressways in foggy mountainous areas,the analysis of foggy environment affecting running speed,visual scope and traffic safety has been done for designing a testing scheme of eye movement of natural driving behavior in foggy environment and another testing scheme of artificial foggy environment.Secondly,the location distribution of driver's fixation point under different levels of visibility has been obtained from the real vehicle test of driver's eye movement,taking advantage of Smart Eye Pro 5.7 eye tracker;the driver's fixation points have been clustered based on the dynamic clustering method.The area of fixation could be divided into six parts,including the left side,the forward vicinity,the forward middle,the forward distance,the vicinity of right side,the distance of right side,and each area is set as the representative of the condition of driver's fixation point;the one-step transition probability matrix has been built based on the Markov chain theory for grasping the transfer law of the condition of driver's fixation point under various visibility conditions,the result of which shown that in the condition of higher visibility,the probability of driver fixating the forward middle area becomes lower.When the visibility VI<50,the visual search concentration ratio is 23.6%higher than it in sunny days,which illustrated that lower visibility leads to more concentrated visual search scope;higher visibility leads to wider range of driver's visual search.Finally,the test of the distance of driver's recognition of traffic signs has been done,mainly relying on the test of natural driving behavior in foggy environment and secondarily relying on the test of driving behavior in artificial foggy environment.Combined with the experimental data,the influence of single factor on driver's recognition distance has been analyzed.The transformation law of driver's target dynamic recognition distance has been obtained,which is that higher visibility results in longer recognition distance,and higher running speed results in more obvious decrease of recognition distance.When the circular curve radius R<1000m and the longitudinal slope i>3%,the influence of linearity on driver's target dynamic recognition distance is significant,which has positive correlation with horizontal curve radius and negative correlation with longitudinal slope.With application of Levenberg-Marquardt method,the model of driver's target dynamic recognition distance in foggy environment has been built,as well as the threshold matrix of driver's target dynamic recognition distance in foggy environment.When the visibility is as low as 50m,the driver's target dynamic recognition distance is only 20m.The research results have provided theoretical methods for relevant researches of the characteristics of driver's visual attention distribution and road transportation safety.Also,theoretical foundation has been provided for formulating the speed limiting values under low visibility on expressways,improving the linearity of expressways and designing traffic signs,in which the practical significance has been shown.