Evaluation of Unassigned Sign Colors for Incident Management Trailblazing

Efforts to design and evaluate a new sign design for incident route trailblazing are reported here. Phase 1 was an off-road field experiment conducted to determine the best sign color combination, letter stroke width, and letter size for emergency signs. Based on the results of Phase 1, three color combinations were chosen for testing (black on coral, black on light blue, and yellow on purple) against a baseline color combination of black on orange. Phase 2 was conducted with an instrumented vehicle through a construction zone-related detour. Questionnaire data were also obtained. The independent variables of interest were sign color combination, age, and visibility condition. The findings of Phase 2 indicated that use of a color combination other than the traditional black-on-orange sign would improve driver performance and safety when used for trailblazing during critical incidents. The following conclusions were reached: (a) yellow on purple or black on light blue will likely result in fewer late-braking maneuvers if the road geometry includes many tight curves; (b) black on light blue will result in the fewest number of turn errors; (c) black on orange will result in more turn errors, especially during the day and particularly when it is overlapped with existing detour and construction zone signs; (d) black on coral is least preferred by older and younger drivers; and (e) younger drivers tend to prefer yellow on purple and older drivers tend to prefer black on light blue.