A Study of the Recursive Blur Technique as a Method to Enhance the Legibility Distance of Symbolic Highway Signs

ii The members of the Committee appointed to examine the thesis of Robert M. McCall Jr. find it satisfactory and recommend that it be accepted. Acknowledgements I would like to take this time to thank a few people who were key players not only in the development of this thesis, but also helped me to grow on personal and professional levels. The first people I would like to thank are my parents Mike and Sallie McCall. Without their constant reinforcement and provision of a growing environment conducive to the sciences, I would never have found the interests which I share with many in our field. I would also like to take time to thank Dr. Frank Schieber at the University of South Dakota Heimstra Human Factors Laboratory. It is through his guidance and mentorship that this research was made possible. Furthermore I would like to thank a couple of people who had to put up with me while the document was under construction. Those people are my good friends and colleagues Peter Shearer and Kevin Limrick. Without those two I would have pulled my hair out a long time ago. Hey guys, first round's on me! Abstract Previous laboratory research has demonstrated that symbolic highway signs which have undergone the Recursive Blur Technique (RBT) of visual enhancement exhibit significantly increased legibility distances when compared to standard symbolic highway signs. This study sought to extend this finding to real-world driving conditions. In order to perform this test a new identification technique known as the holistic identification protocol had to be tested under laboratory conditions. The experimenters used both stimuli which had previously shown improvements in the laboratory and some which had not been previously tested. The study was able to replicate the findings of previous research with an identification task which required the participant to report the critical details of the stimulus object to the experimenter. When using the more global (holistic) identification protocol the legibility enhancements due to RBT proved to be only marginally significant. The pattern of results appear to reflect the dominant role of top-down strategies when using the global protocol, while bottom-up mechanisms set the limit of performance in the critical detail protocol. It is the belief of the researchers that only minor modifications to the identification task protocol will be necessary to test the hypotheses of RBT enhancement on the road.