Traffic sign comprehensibility in an aging society: A Study of "photo-enforced traffic signal ahead" signage

This paper analyzes the comprehensibility of current and experimental signs to indicate a photo-enforced traffic signal ahead. In Arnold, Missouri, four signalized intersections are photo enforced and have been indicated with the text-only "photo-enforced" regulatory sign posted below the traditional "signal ahead" warning sign. These signs were replaced with an experimental sign that indicates a photo-enforced traffic signal ahead with a single regulatory sign. The evaluation is performed by using three surveys: one for the currently approved signage and two for the experimental sign. The second survey was conducted shortly after installation of the experimental sign, and the third survey was conducted about 9 months after installation. The study found that older drivers (age 65+ years) have greater difficulty in comprehending both the current and experimental photo-enforced signage compared with younger drivers. However, older drivers' comprehension of the experimental sign improved more over time than other drivers' comprehension (62.5% to 75.8% correct comprehension for older versus 79.8% to 81.2% for others). The results indicate that the experimental sign has the potential to improve safety by better delivering its intended meaning, particularly to older drivers, but also that it may take older drivers more time than other drivers to learn about and comprehend new signs.