Improvement of Conspicuity of Trailblazing Signs: Phase III-Evaluation of Fluorescent Colors

This report represents a Phase III effort to design and evaluate a new sign design for incident route trailblazing. The colors evaluated were fluorescent coral, fluorescent purple, fluorescent yellow-green, and non-fluorescent purple. The results indicate no significant differences in driving performance with regard to the four experimental sign color combinations. Regarding the subjective preference questionnaires, significant questionnaire results along with trend information suggest that black on fluorescent yellow green was the most preferred by younger and older drivers during both day and night visibility conditions. Nonetheless, this sign color has been assigned by FHWA for pedestrian, school, and bicycle crossings, which eliminated the opportunity to use fluorescent yellow-green as a unique sign color for trailblazing in incident management situations. Preference for non-fluorescent yellow on purple consistently increased at night when the sign became more luminant; however, the overall preference for this sign color combination was lower than for the other sign color combinations tested in this study. With the elimination of these two signs, the remaining contenders for a unique sign color combination were black on fluorescent coral and fluorescent yellow on fluorescent purple. Black on fluorescent coral was ranked significantly higher than fluorescent yellow on fluorescent purple for visibility and for overall preference. Questionnaire trend information suggests that black on fluorescent coral was more preferred than fluorescent yellow on fluorescent purple during daytime viewing conditions and less preferred than fluorescent yellow on fluorescent purple during nighttime viewing conditions. The overlay film used for the fluorescent coral sign was a first generation material that can reasonably be expected to result in improved nighttime luminance when produced in a full production run. In addition to the study results, drivers commented that the arrow on the sign was too small to determine directional information from a comfortable distance. Based on such driver comments, the research conclusions, and the federal regulations enacted since the outset of this series of experiments, the following recommendations are made: (1) black on fluorescent coral should be used as a unique incident management sign color, and (2) the directional arrow on the sign should be larger.