Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Human Factors Psychology

Committee Chair/Advisor

Dr. Richard Tyrrell

Committee Member

Dr. Benjamin Stephens

Committee Member

Dr. Christopher Pagano

Committee Member

Dr. Shubham Agrawal


Nighttime pedestrian fatality rates in the U.S. continue to rise. Nighttime visibility aids – including retroreflective garments – can enhance the conspicuity of pedestrians to drivers at night. Yet, pedestrians rarely take advantage of retroreflectivity and instead often wear fluorescent garments that are not useful at night. This research explored whether road users’ misunderstandings of two critical principles – retroreflectivity and fluorescence – support the misuse of visibility-enhancing garments. This project also explored whether materials that combine retroreflectivity and fluorescence (“combined-performance materials”) circumvent road users’ misconceptions. Two experiments quantified observers’ expectations for how bright fluorescent, retroreflective, or fluorescent-retroreflective materials will appear to nighttime drivers. In Experiment 1 observers who received an educational intervention concerning fluorescence and retroreflection more often correctly selected an image of a pedestrian on a road at night that depicted fluorescent materials appearing dark and retroreflective materials appearing bright. Observers in Experiment 2 utilized a magnitude estimation technique to explore road users’ brightness perceptions of materials with different reflective properties. On average, observers overestimated how bright fluorescent cotton stimuli would appear, underestimated how bright retroreflective stimuli would appear, but correctly estimated how bright fluorescent-retroreflective stimuli would appear. These experiments reveal that a brief demonstration of retroreflectivity effectively encourages behaviors that improve the conspicuity of road users who interact with traffic at night. Further, combined fluorescent-retroreflective materials may produce higher adoption rates of garments that enhance nighttime conspicuity even when their users may not understand underlying fundamental principles.



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