A literature search was conducted in the field of visibility using this term as a warning against stationary or moving hazards. The review was conducted to establish the extent of research conducted on the Visibility Index. This Index was designed to provide the method for examining the effective value of such properties as color, texture, pattern, contrast, and other variables which can be used to improve the effectiveness of warning devices, signs, labels, and markings aimed at providing increased safety through visible means. Future research was to be conducted in order to evaluate the effectiveness of increasing visibility as a means of reducing the hazard of a worker being struck or injured because he was not able to see a hazard in his path. References were cited for existing standards for visibility in the U.S. and foreign countries along with international standards. Other areas for which references were listed include current practices (air and ground transportation, safety clothing, underwater visibility, visibility measurement, and industrial and occupation applications), design factors (camouflage, pattern recognition, color contrast, luminance contrast, area, and reflectivity), and environmental variables (illumination, background, types of lighting, distance and moving targets).