Adding Graphics to Dynamic Message Sign Messages

Abstract

A human factors study assessed the effects of adding graphics to dynamic message sign (DMS) messages. Two approaches employed in the assessment—a questionnaire survey and a video-based driving simulation experiment—are reported here along with the findings. The questionnaire surveyed drivers’ preferences concerning the addition of graphics to a text message, the color of the message, alternative graphic images, placement of the graphic image, image contrast, flashing, and the framing of graphic images. One hundred and twenty-seven subjects from Rhode Island participated in the survey. Statistical analysis of survey results showed strong preference for graphic-aided messages over text-only messages; amber-color messages over green- and red-color messages; and messages with graphic on the left side over others. The analysis also identified specific graphics to accompany certain text messages. Based on the survey results, a video-based driving simulation experiment was designed to test drivers’ responses to selected DMS messages surveyed in the questionnaire. Forty-eight subjects from different age groups with different native language backgrounds took part in the experiment. Results of the experiment showed that graphic-aided messages displayed in amber or green were responded to significantly faster than other settings. Older drivers’ responses were slower and less accurate than others; however, their responses improved significantly when the DMS messages were enhanced by graphics. It was also found that graphic-aided DMS messages helped improve the responses of non-native-English-speaking drivers.