“…Educational level [ 7 , 8 ] and prior training [ 3 , [9] , [10] , [11] , [12] , [13] ] also improved comprehension levels. The effects of cultural differences on comprehension of graphic symbols have been demonstrated by several researchers [ [14] , [15] , [16] , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] ]. The design characteristics of a sign (i.e., color, shape, pictogram, size, visibility, readability, and comprehensibility, as well as the placement, illumination, and maintenance of the sign) and working conditions (i.e., dust, chemicals and fumes in the air, precipitation, time pressure, and performing multiple tasks simultaneously) can also affect the comprehensibility of a sign.…”