The time duration for which drivers observe signs while in motion is short; between 0.1-0.5 sec. The optimum brightness of exposed lamp signs and the legibility threshold for this short period recognition must differ from that for longer period recognition. This study is aimed at clarifying the relationship between duration of presentation for exposed lamp signs and legibility threshold. The results show that as duration of presentation decreases, legibility threshold increases, and the legibility threshold at duration of 0.1 sec. is double of that at 0.5 sec. Furthermore, as duration of presentation decreases from 0.5 to 0.03 sec., the quantity of light at the legibility threshold reduces.
ASJC Scopus subject areas