Brainard, R. W., Campbell, R. J. & Elkin, E. H. (1961). Design and interpretability of road signs. Journal of Applied Psychology, 45(2), 130-136.

(Summary and conclusions.) The purpose of the present study was to investigate the interpretability of selected European road signs, to determine if stereotypes existed for signs, to compare the general characteristics of the European signs with the characteristics embodied in the stereotypes, and to determine if stereotype-based signs enhanced interpretability.

Interpretability was investigated by two different methods. In Phase I Ss wrote the meaning which they thought a sign conveyed, and in Phase II they chose from a list of possible meanings the one meaning which best matched the particular sign being shown. In Phase III, the same Ss who had participated in Phase II were told the meanings of the signs. Then the signs were presented again and Ss wrote the meaning which they thought the sign conveyed. Phase IV investigated the stereotypes for road signs. In this phase, sign meanings were read to Ss, and they designed signs which would convey these meanings. Stereotype-based signs were constructed from the results of Phase IV; the interpretability of these signs was determined in Phase V.

The results of the study can be summarized as follows:

1. Interpretability of the European signs was partly a function of the method by which interpretability was examined. The mean interpretability score from Phase I was considerably lower than for Phase II, although the correlation between the two methods was significant.
2. The European signs were moderately well interpreted on first presentation; after one exposure to the correct meaning, interpretability approached 100%.
3. The easily interpreted European signs were generally pictorial representations of the sign meanings or were counterparts of American road signs. The signs which were difficult to interpret generally used abstract, unfamiliar symbols or included ambiguous cues.
4. Stereotypes for some road signs exist. The general characteristics found in the stereotypes were the same as those in the easily interpreted European signs.
5. Interpretability is enhanced if signs are stereotype-based. However, signs based on stereotypes of only moderate strength (30-40%) will not always be highly interpretable.
6. A small number of the European road signs could be efficaciously used in the United States, without necessitating prior instruction as to their meaning. The majority of the signs, however, could not be used without a minimal degree of familiarization.