drivers are often not able to recognize the letter in time and sometimes it is a waste of money with too large letters in guide signs. In order to solve this problem, a new Chinese character height model for guide signs has been developed based on 3D technology and the apperceive characteristics of Chinese drivers. The model was built according to the visual and kinematic theory based on the legibility process of drivers. Then the key parameters of the model were validated by some special designed simulation experiments. The experiment was designed to determine the minimum visual angle needed. The relationship between the information units and the reaction time was studied based on 3D technology. The disappearing distance was computed according to the geometric relationship concerning about road width, the height of the sign and the disappearing angle. In the end, the letter height for various design speed was computed and compared with the value specified in the standard. The results revealed that the height value of Chinese characters in guide signs which was computed in the model has a relatively good consistence with the current value in national standard, but the value in the standard is a bit small for high speeds and high for low speed. The model of Chinese letter height was built at the first time and it is projected to play a big role in the traffic safety.
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