Legibility and Comprehension of Traffic Sign Symbols

In recent years, symbols have been used to improve the ability of traffic signs to communicate their messages. A study of traffic sign symbols was recently completed at the Federal Highway Administrations Turner-Fairbanks Highway Research Center in McLean, Virginia. In this study, a laboratory experiment was conducted to determine the relative legibility distance and driver comprehension for 22 symbol warning signs currently in use in the United States. The results showed that the legibility distance of symbols decreases with increasing driver age and that bold symbols of simple design provide the best legibility distance for all age groups. This study also showed that the legibility distance for symbolic signs can be equal to that of alphabetic signs or have as much as 4 times greater legibility distance depending on the message. The sign comprehension data indicated several symbols need redesign or increased driver education efforts.