Determining Colors for Traffic Control Devices at Transponder-Controlled Tollbooth Lanes with a Sign Simulator

The number of toll roads is increasing in the United States, and drivers face signing practices that vary greatly across jurisdictions. In addition to the increase in toll roads, there is an increase in the use of electronic toll collection (ETC) transponders. The present study was undertaken to develop standard signing practices—specifically for background color, legend color, underlay color (i.e., the background color for the pictographs), and pictograph—for ETC-supported toll road signs. The study reviewed selected ETC toll road signs in the United States to help select candidate elements and options to be used in a laboratory experiment. On the basis of that review, 120 signs depicted on 35-mm slides were developed with a standard sign-design software package. The signs were presented to 60 participants (equally divided by sex and age group) in the recently updated Turner–Fairbank Highway Research Center's sign simulator. The signs were shown to participants starting at a simulated distance of approximately 1,125 ft (343 m), and then the image was zoomed toward the participants at a constant speed controlled by the laboratory's computer. Each participant's detection distance, guidance legibility distance, and pictograph legibility distance were recorded. The results showed that, overall, green as a background color obtained the longest guidance information legibility distance. Also, fonts that provided the highest contrast to the background color (such as white on black) were the most effective for legibility. Underlay colors that showed the highest contrast to the pictographs were the most effective and included all of the lighter colors tested (white, yellow, and blue).