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29 Figure 32. Photo Set 5--rural 2. visual prominence is necessary to achieve a noticeable change change (either recessed or protruding) can be accomplished in the way a barrier or rail is perceived by the viewer. without affecting the behavior of impacting vehicles?" In all the graphic studies, the features that most affect impacting vehicles appear to be: ASSESSMENT Depth and frequency of shadow forming by vertical ele- The study designs suggest that: ments in the barrier face. Thickness of protruding elements that form patterns in Background plays a significant and critical role in how the barrier face. the barrier is perceived. The angle of the edges of shadow-producing elements. The linear character of barrier rails can be significantly modified through the use of line and contrasting forms. Determining these features will allow the development of Relatively small elements or openings near the top or near detail-specific guidelines that, when coupled with context- the bottom of the barriers can significantly change the sensitive design rules, can be applied to any alternative design character of the barrier. in any situation. The aesthetic character of see-through rails should be The previous sections of this report have provided informa- secondary to the background scene. tion on the state of the practice regarding defining aesthetics for barriers and assessing and using aesthetic treatments on The degree that these findings can be applied is determined concrete barriers. This information was obtained by review- by established, critical parameters. ing the literature and surveying state DOTs, roadside safety researchers, and crash-testing laboratories in the United States AESTHETIC DESIGN DISCUSSION and internationally. The remainder of this report presents the methodology used for developing design guidelines for aes- There can be a very large number of design variations for thetic concrete safety shape barriers based on finite element barriers and rails. The most important question to be answered simulation and full-scale crash testing of specific asperities in this and all other designs is "how significant of a surface cast into the face of concrete safety shape barriers.