Variable message signs (VMS) installed along traffic corridors are used to communicate advisories and other information to motorists, such as estimated travel times to downstream destinations. While most VMSs have historically been monochromatic, displaying text in a single color on a black background, Pennsylvania Department of Transportation (PennDOT) commissioned a research effort to evaluate the visibility and comprehension of alternative VMS formats including multiple text colors and graphical elements. Researchers conducted a two-part lab experiment with 75 participants viewing realistic images of VMS travel time messages on a screen, and measuring the comprehension time and accuracy when presented with a variety of VMS formats, including monochromatic and multi-color messages. The participants’ reaction time and distance to identify the route with shorter travel time, and correctness of the response, were recorded for statistical assessment using Analysis of Variance (ANOVA) tests.
- Generally, utilize monochromatic (e.g., amber text on black background) designs for VMSs displaying travel times. Reaction times are lower for monochromatic designs than for color formats. Monochromatic designs reduce reaction time for all driver populations.
- If using color VMSs for displaying travel times, use color only for displaying the travel time of congested roadways in red. Overall, although it was found that color VMS formats did not perform statistically better than monochromatic signs, some formats performed equivalently in comprehensibility and visibility. The best use of color formats in the study was observed in the display of travel time for congested segments in red, which yielded good results in sign visibility and comprehension.
- Display route numbers as numbers rather than graphical shields. Using route numbers as text rather than graphical shields was found to have statistically shorter times for driver comprehension regardless of driver gender, age, and colorblindness. There was no improvement in comprehension observed for displaying route numbers as shields.