A number of treatments for making signs more conspicuous were compared in a laboratory experiment. Three involved placing the sign on a plain square backing board (three colours were tested: black, light grey and yellow) and a fourth used a larger version of the sign having the same area as the basic sign plus backing board. Slides showing the signs against three backgrounds were projected on a screen for fixed time periods of between 100 and 250 msecs. Subjects were required to locate the signs while performing a continuous steering task. The most effective overall treatment was the use of a yellow backing board. This and the grey board were about equally good against foliage and grey was only marginally inferior against a street scene with potentially distracting coloured detail. However, against a background with high luminance contrast, tree trunks seen against a bright sky, the yellow board was markedly superior to any of the other treatments. It is concluded that the contrast between backing board and background is a more important factor in determining conspicuity than sign size. (A)

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