The change rule of visual field in the dynamic environment is analyzed,and legibility distances are meas- ured under different velocities by dynamic experiments The results of experiments show that the effects of velocity on the legibility distance are not significant below a velocity of 120km/h,and the results are also analyzed with the theory of psychology and vision.

According to the common problems exist in setting highway traffic signs and analysis on them,giving calculation formulas for density of settings and distance of visual cognition under the common situation.

Through generalizing related literature,we summarized some properties of cognitive distance and reduced all research on this concept into two aspects: pure value,and real cognitive distance.

Having summarized the sorts of icons and analyzed the problems of the interfaces in common softwares,this paper pointed out that the cognition distance could be shorten determineed success in icon design.