Assessment of Workplace Safety Symbols

Written signs are commonly used in industrial sites to provide hazard warnings and safety information. The use of safety symbols and pictorials may increase the effectiveness of safety communication, however, because such signs are language-free, and because they can be recognized more rapidly and accurately even under some conditions of interference and distraction. The effectiveness of safety symbols critically depends upon the selection of symbolic images which are readily understandable to the intended audience. A three-phase evaluation of a set of selected workplace symbols is described in the following paragraphs. First, thirty-three messages (referents) important to workplace safety were selected, based upon industrial site visits, sign catalogue review, and safety standard examination. These messages were divided into five categories: hazards; protective gear; first aid and emergency equipment; prohibited actions; and egress. Secondly, two to forty symbolic images were collected for each of the thirty-three referents. These images were rank-ordered according to their appropriateness for a given referent by thirty participants drawn from the graphics and safety communities. Three to five images for each referent (for a total of ninety-one images) were selected from the preference rankings for further experimentation, except for five messages where nationally standardized images already exist. These include laser, biohazard, radiation, fire extinguisher, and standpipe. The final set of images for each referent represented a range of abstraction, complexity, activity, and use of the human figure. (It was hypothesized that less abstract figures engaging in activity might be better understood.) The final phase consisted of two portions: determination of understandability and preference ranking. In the first portion, participants from industrial sites in three disparate geographical locations provided a short definition of the meaning of each image. The images were shown one at a time in a random order. Subjects saw only one symbolic image for each referent. Secondly, all the images for each referent were presented along with the meaning, and participants selected the image that best conveyed the intended meaning and indicated any reasons for the preference. Similar data were obtained from a pilot group of participants who were not familiar with workplace hazards, so that the effects of workplace experience on symbol understandability could be examined. Symbol understandability, in terms of percentage of correct responses and confusions, varied widely for the thirty-three referents and for the images tested for each referent. Despite standardized use for a number of years, the radiation, biohazard, and laser symbols were frequently mis-identified. Symbols for protective gear, first aid and emergency equipment were generally correctly identified. The different images selected for various hazards show the greatest range in understandability, with versions for entanglement, electricity, corrosion, and overhead hazard being quite different. Referent messages for which all symbolic versions received less than 85% correct responses included radiation, laser, biohazard, general warning, poison, combustible, eyewash, exit, no entrance and no exit. The first four referents do particularly poorly for both informed and naive participants. The preference data generally supported the understandability data, with the most correctly identified image usually being the most preferred image. Participants also provided insightful comments about the reasons for their choices, including ideas about the visibility, representativeness, and effectiveness of the images proposed for each referent.