There is an important relationship between the visibility and the degree of traffic sign and the shape of traffic sign. In appearance, the same area, the effect is good and easy to identify the sequential: triangle, diamond, square, is pentagonal, hexagonal, round and octagonal.
Is the "Safety colours and safety mark" draft standard provisions regarding geometry: is represented as a triangle warning: circular said prohibitions and restrictions; square, rectangle representation of cue; circular pattern with a slash, also said the ban. The international standard of traffic sign geometry and the standard of "safety sign" in our country are basically the same.
A triangle. Show a high degree, regardless of the condition of the light is good or bad, are more eye-catching than other shapes. In our country, the geometric shape of the warning sign is used as a warning sign, in which the "stop to give way" and "the slow line give way" are used.
The circular. Round display degree is higher, the vision is big, also is easy to arrange the text, our country will circle the geometry shape which is used to prohibit and indicates two kinds of marks.

The square. Including rectangular and square, its visibility, for the direction of the traffic signs of the geometry.