Effects of pictorial size and circle-slash thickness on glance legibility for prohibitive symbols

Abstract

The purpose of this study was to investigate the effects of pictorial size and thickness of the red-circle slash on glance legibility for prohibitive symbols under different figure/ground luminance contrasts and limited exposure times. Analyses showed that the two-factor interactions of luminance contrast and exposure time; luminance contrast and pictorial size; luminance contrast and slash thickness; exposure time and pictorial size; and pictorial size and slash thickness were significant. Under higher luminance contrast (1:20) or longer exposure time (50 ms), the effects of pictorial size and slash thickness were not significant. Under degraded situations resulting from the reduction of luminance contrast of the symbols or limited exposure time, pictorial size and thickness of circle slashes influenced glance legibility. Glance legibility for the 100% and 75% pictorial sizes did not significantly differ, but glance legibility for the 50% size was significantly lower. Moreover, glance legibility for the 25% and 35% thickness of the red-circle slash did not significantly differ, but glance legibility for the 45% thickness was significantly lower. Relevance to industry A red circle with a slash is used extensively to convey that some activity or thing is forbidden. The design of prohibitive symbols may profoundly affect their efficiency and effectiveness in communicating the desired message. This article provides recommendations to improve the design of prohibitive symbols.