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Federal Highway Administration Research and Technology
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Publication Number: FHWA-RD-95-129
Improvements In Symbol Sign Design To Aid Older Drivers
The proportion of American adults age 65 and older is expected to comprise 20 percent of the population by the year 2020. Studies have shown that older drivers have higher rates of accidents, injuries, and fatalities on a per-mile-driven basis. A major cause of roadway accidents for older drivers is failure to heed traffic signs.
Previous research found that older drivers have difficulty detecting, reading, understanding, and responding to some symbolic traffic signs. This study had four objectives:
The study was conducted in two phases of laboratory investigations. The first phase assessed daytime visibility and comprehension of all 85 of the symbols in the MUTCD. Based on these results, a sample of 18 symbols (6 "best," 6 "intermediate," and 6 "worst") were selected for further testing of glance legibility, reaction time, and conspicuity.
The second phase investigated comprehension plus daytime and nighttime legibility distance measures for 14 modified and 5 novel symbol signs. The purpose of this phase was to improve visibility, especially for older drivers.
Phase I results found: (1) older drivers' comprehension of symbol signs was poorer than both younger and middle-aged drivers; and (2) older drivers' legibility distances were shorter. These findings were especially true of recreational (?) and cultural signs, where the symbols are ambiguous and background color tends to provide poor conspicuity.
Phase II results from the modified and novel sign studies found that sign modification did little to improve comprehension, which was from 67 to 100 percent across all signs. Table 1 shows Phase II legibility distance results. Overall, the degree of improvement for the redesigned signs was greater than for the modified signs, and the redesign was especially helpful for the least legible signs.
Based on the experimental results and the redesign techniques employed in the study, a number of guidelines have been suggested. These include:
For More Information
A full report on symbol sign design is available from the FHWA R&D Report Center, phone no. 703 285-2144.
This research was conducted by Swanson Transportation Consultants, Inc. For more information, contact: