LEGIBILITY OF TRAFFIC WARNING SIGNS BY DRIVERS

Abstract

This study aimed to investigate the minimum sizes of traffic signs that young and elderly drivers could recognize and also to see if the distance for recognizing those signs are more than the required minimum distances of MOTC (Ministry of Transportation and Communications, R.O.C) regulation. Experiments were carried out in a laboratory. Twenty-four elderly and young subjects separately participated in the study. The method of limits was employed to find the absolute threshold. In the experiment, various traffic signs were displayed on the screen with the size enlarging from small to big until participants could recognize the sign. The size of the recognized stimulus was recorded and then transformed into visual angles. The results show that the legibility capabilities of elderly drivers are indeed poorer than young subjects. Average visual angle of elderly group is about 1.6 times of that of young group. Ideogram signs can be better recognized by all subjects compared to the pictogram ones. When at speed limit of 90 km/hr, the minimum distance for recognizing all the signs cannot satisfy the requirements of the regulation. Based on the results needed sign sizes and changing sign location are proposed. Keyword: The Elderly; Traffic Signs; Legibility; Warning Signs; Ideogram.