Book excerpt: This report represents efforts to design and evaluate a new sign design for emergency route trailblazing in a two-part series. Study was an off-road field experiment conducted to determine the best sign color combination, letter stroke width, and letter size for the emergency sign. Based upon the results of that first study, 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. The test signs to be further tested featured D series, 125-mm (5 in) height letters. Study 2 was conducted using an instrumented vehicle and survey questionnaire through a construction zone-related detour. The independent variables of interest were sign color combination, age, and visibility condition. The findings of Study 2 indicated that use of a color combination other than the traditional orange background with a black legend will improve driver performance and safety when used for trailblazing during critical incidents. Based on the conclusions and other anecdotal evidence, the following recommendations were made: 1. Do not use a black on orange sign for trailblazing around a critical incident if an existing detour/construction zone is in place. 2. Do not use a black on coral sign for trailblazing around a critical incident. 3. A black on light blue sign is recommended due to its generally favorable subjective ratings and for minimization of the number of turn errors made by drivers in an overlapping detour. 4. Despite recommendation 3, it is important to note that the black on light blue sign fades to take on the appearance of a regulatory sign when headlights reflect onto it. 5. If the black on light blue sign is deemed inappropriate due to its appearance as a regulatory sign at night, consider using the yellow on purple color combination. In this study, the yellow on purple sign color combination resulted in fewer turn errors than black on orange and it was generally rated favorably by drivers, especially younger drivers.