A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand.

Thesis (M.Eng.) - Asian Institute of Technology, 1968

The objective of this study was to determine the relationship between the duration of glance exposure and the projected height of Thai characters used for highway place-name signs. Glance legibility of signs was measured from slides projected onto a screen at 7.5meters prospection distance. Six values of exposure (5, 2, 0.5, 0.2, 0.1, and 0.04 sec) were employed, and 30 subjects were tested under simulated driving conditions. The 30 place-name signs were classified into three groups, having high, moderate, or low levels of legibility in accordance with the consistency of their legibility at various durations of exposure. The results were stated as a regression equation for each group of signs, the regression line relating projected height of characters to the duration of exposure. From the group of signs which gave consistently high legibility, the results led to determination of the most legible design of Thai characters by evaluation of the width/height and character-spacing/height ratios. An attempt was made to study the amount of learning in recognition of place names. The six runs of the slides of signs exposed for the present study were compared with the findings of an earlier experimenter in which a particular group of subjects viewed a set of the slides only once. The effect of familiarity with the signs was statistically analyzed by finding the linear relationship and the degree of correlation between these two independent, but generally similar, sets of data.