AGE EFFECTS ON SYMBOL SIGN RECOGNITION

The use of symbolic road signs is proliferating on the highways, and the Federal Highway Administration is concerned with their effective use, particularly by the elderly driving population. This report describes an experimental study of problems encountered by a broad age range of drivers in learning and retaining symbolic information. A driving simulator was used to present 72 symbol signs to subjects during 25 minute "drives." Performance measures included the correctness of sign recognition, and the distance from the signs at which recognition took place. The experimental design looked at the effects of age, training, and sign format on the learning and retention of symbol knowledge. Subjects received three simulator trials, the first to determine initial symbol knowledge, a second immediately after symbol training to determine the amount of learning, and a final trial week or so later to measure symbol knowledge retention. Sixty subjects were divided into four age groups (age range 20-79 years). The age groups were further subdivided into three training subgroups, each receiving a different symbol training treatment. The overall results showed strong age effects, but no influence due to the type of symbol training employed. All age groups learned and retained roughly the same number of symbols, but the older age groups started off with less symbol knowledge initially. Data interpretation also indicates the older subjects required longer recognition and response times. Recognition performance differences between signs were also analyzed. The 72 symbol signs were equally subdivided into six MUTCD sign categories of 12 signs each, with each category representing a different color code. Recognition response differences were apparent between sign categories and were attributable in part to differences in requiring processing time. Symbology appeared to lead to appreciable differences in both response distance and correctness, with simple, bold, unique symbols giving the best performance. (FHWA)