This document represents efforts to design and evaluate a new sign design for emergency route trailblazing in a two-part series. Study 1 was an off-road field experiment conducted to determine the best color combination and letter design for the emergency sign. Based upon Study 1 results, black on coral, black on light blue, and yellow on purple signs were chosen for further testing against a baseline black on orange sign, all with 125-mm, D series letters.

Study 2 was an on-road field study of conspicuity, conducted using an instrumented vehicle through a construction zone-related detour, and a survey questionnaire. The findings indicated that use of a color combination other than traditional black on orange 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 black on orange signs 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 light blue on black sign is recommended due to generally favorable subjective ratings and for minimization of turn errors in an overlapping detour; however, the black on light blue sign may resemble regulatory signs when headlights reflect onto it; and 4) If reject black on light blue signs based on (3), consider using yellow on purple signs, which resulted in fewer turn errors than black on orange and received generally favorable ratings.