Accompany Graphics with Text on Dynamic Message Sign (DMS) Messages to Improve Conspicuity, Comprehension, Ease of Use, Compliance Intent, and Memorability.
Driving Simulator Study Examined How Graphics and Text Affected Drivers’ Understanding of DMS messages.
Kansas, United States
Creating Effective Graphic Changeable Dynamic Message Sign (DMS) Messaging
Summary Information
Dynamic Message Signs (DMS) are widely used to deliver real-time safety and traveler information on highways. However, text-only messages may be difficult for drivers to understand and the effectiveness of graphic-based DMS messages remains unclear. This study evaluated the effectiveness of graphic DMS designs with and without accompanying text, using a driving simulator and questionnaires based on several measures: conspicuity, comprehension, ease of use, memorability, and intention to comply. A total of 46 individuals participated in the study, which tested 36 graphic messages, including 18 graphics with text and 18 graphics without text, using 10-second video recordings generated for each graphic. These messages included crash and incident information, alternative route guidance, adverse weather warnings, work-zone and road-closure information, and general safety messages. The simulated DMS was placed 800 feet from the driver’s viewpoint, providing approximately eight to 9.8 seconds of visibility at 55 MPH under daytime conditions. After viewing each sign, participants answered a set of questions designed to assess their understanding and collect the measures of interest.
- Accompany graphic DMS messages with text descriptions. The results of this study showed that signs that included text performed better than graphic-only signs across all measures of interest, including conspicuity, comprehension, ease of use, intention to comply, and memorability than signs without text.
- Graphic-only signs may be less reliable when drivers need to interpret messages quickly. Lower-performing signs were generally associated with weaker interpretation accuracy, lower ease-of-use ratings, and reduced intention to comply.
- Adding text can help reduce differences between native and non-native English speakers. Without text, several effectiveness measures differed significantly between the two groups. When text was included, differences in interpretation accuracy and intention to comply were reduced, suggesting that text support is especially important for non-native English-speaking drivers.
- Account for differences in how age groups perceive and process visual highway messages. Drivers aged 41 and older showed higher effectiveness scores across several measures, including conspicuity, interpretation accuracy, comprehension time, ease of use, and intention to comply. This suggests that DMS design should account for differences in how age groups perceive and process visual highway messages.
