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3 becomes more cluttered, the conspicuousness of traffic con- in which humans perceive their environment and how they trol devices worsened.(13) This condition is termed visual may combine to predict a particular response: complexity, co- complexity and occurs when the background and the number herency, legibility, and mystery. of objects in the scene combine to the point of creating an Complexity is defined as how much is going on in a scene information load that is excessive, confusing, or ambigu- as determined by the diversity and number of elements. ous.(14) The size of objects and their edge contrast are impor- Coherency (i.e., how easy the picture is to organize or tant determinants of conspicuity.(13) Contrast and luminance comprehend) is based on the patterns of light and dark and of the object with respect to the background and the sur- how many major objects or areas these form. Readily identi- rounding area have a great impact on the perceptibility of fiable objects result in greater coherence. Kaplan notes that objects.(11,15) Brighter colors are recommended as a tool to humans can hold only so many major units of information or increase both conspicuity and contrast.(10,16,17) "chunks" at one time and that research indicates five such The studies cited deal with making specific elements more units is the norm. visible (in particular, critical traffic control or driver perfor- Understood in these terms, it is easy to see the relationship mance information) but do not apply this approach to aes- between complexity and coherency. A scene can be complex thetics. A basis is developed in a study from Japan.(8) This (i.e., have a lot of things in it) but still be coherent (i.e., arranged 3-year study looked at the issue of visual complexity in the in a few large chunks). This suggests that in visually complex view of the roadscape as a whole. scenes, ways might be sought to define logical areas as dis- The study was specifically looking at the degree of visual tinct units. This may be done by screening some elements, image perception at the stage before cognition. In other using textures or colors to separate important elements from words: "what you see" before "what you know." It found that the background, or removing some elements to create a sim- there is a hierarchical structure of articulation for elements pler visual unit. versus backgrounds. The pavement is registered first, elements Legibility is making sense of three-dimensional space with forming the skyline such as buildings or trees appear second, the intention of functioning safely within it. A highly legible and roadside elements--including utility poles, pedestrian scene is described as one that is easy to oversee and cogni- bridges, advertisement--are noticed last. tively map. Depth and well-defined space increase legibility. This hierarchy is established by virtue of the "conspicu- Landmarks, for example, increase legibility by providing ousness" of the element that determines whether it is seen as easy understanding of one's position relative to prominent an element of the scene or a background for other elements. elements. In the study it was found that a roadscape in which buildings Mystery involves the anticipation of something to come or other large structures are perceived early and are very con- next based on the present scene. This concept relates to the spicuous would receive a low aesthetic evaluation rating. concepts of novelty and surprise. In the highway environ- Greenery such as trees rated high in the evaluation when they ment, a degree of novelty may be appropriate in special cases are the conspicuous part of the scene. A key to determining (as in art pieces), but surprises in the driving environment are conspicuousness was which element formed the background highly undesirable. Kaplan defines scenes that are high in against the skyline. The authors summarize: "Although con- mystery as being characterized by continuity, a connection ditions may differ by case, it is undesirable in terms of safety between what is seen and what is anticipated, creating a and amenity that such components, with no direct relevance promise of new information. to vehicle driving behavior, are perceived more strongly than Kaplan's model of visual perception and interpretation the pavement, which is of major importance or greenery, and their relationship to a response or an action offers a sim- which relates to the emotional dimension." ple method to evaluate aesthetic design in the roadway. It can This work stresses that the elements of the scene must be form the basis for identifying not only how a proposed addressed before the meaning of the scene can be effectively enhancement may affect the scene but also how a scene may conveyed. Also, the elements must first serve the needs of be improved based on the degree of conspicuity within a driving behavior. In terms of longitudinal barrier design, this visually complex scene. finding suggests that the aesthetics of any structure must be considered in terms of the context in which it is viewed. This issue of complexity as it relates to aesthetics was fur- SUMMARY OF LITERATURE REVIEW ther explored and explained by Kaplan.(6) Using her own and the work of others in the field, Kaplan created a framework Unfortunately, the application of much of this information that offers insight into the design and management of the nat- to the realm of highway aesthetics is incomplete if not non- ural environment. Although heavily focused on the natural existent. Studies showing the effect of a particular aesthetic environment, the concepts employed embody many basic treatment and its effect on driver performance cannot be design rules that are applicable both for aesthetics and for found. The literature regarding aesthetics in highway design perception and communication by and to a highway user. typically discusses the issue through the use of case studies and Kaplan used four informational factors to describe the way the presentation of imagery of noteworthy structures. These