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Federal Highway Administration Research and Technology
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Publication Number: FHWA-RD-94-069
Date: July 1997
Symbol Signing Design for Older Drivers
There has been an increasing use of symbols, including those on highway signs, over the past 2 decades. At the same time, there has been a rapid growth in both the numbers and proportions of older drivers. Research on symbols has shown that many symbols are poorly understood and/or difficult to recognize at a distance, especially by older drivers. In spite of the considerable research on traffic sign symbols, there has not yet been a thorough evaluation of all symbols used on U.S. highways.
This report presents a review of the literature on information processing abilities of older drivers and human factors research on traffic sign symbols. It describes a series of studies, surveys, and laboratory experiments that examined symbols in the U.S. Manual on Uniform Traffic Control Devices (MUTCD). Initially all symbols in the Manual were evaluated for comprehension and daytime legibility distance among drivers of all ages. This was followed by evalation of a set of 18 symbols using measures of nighttime legibility (with and without glare), reaction time, glance legibility, and conspicuity. Older drivers were found to have poorer understanding of the symbols, as well as shorter legibility distances, higher glance legibility thresholds, reaction times, and conspicuity search times. Glare was found to reduce legibility of signs only for older drivers. Modifications and redesigns to 13 of the symbols resulted in better understanding of 3 symbols and increased legibility of 11 new designs. Understanding and legibility of five novel symbols which were developed for this project were found to be comparable to those of the redesigned symbols.
Recommendations were made for changes to specific symbols and guidelines were proposed for the design of symbol traffic signs. A proposal was made for the use of design optimization techniques, using computer, in the development and evaluation of signs.
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TECHNICAL REPORT DOCUMENTATION PAGE
Form DOT F 1700.7 (8–72) Reproduction of completed page authorized
Keywords: symbols, traffic signs, comprehension, Legibility distance, glance legibility, reaction time, conspicuity, older drivers, night legibility, glare