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Aesthetic Concrete Barrier Design (2006)

Chapter: Chapter 2 - State of the Practice

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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
×
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
×
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
×
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
×
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
×
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
×
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
×
Page 12
Page 13
Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
×
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
×
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Suggested Citation:"Chapter 2 - State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2006. Aesthetic Concrete Barrier Design. Washington, DC: The National Academies Press. doi: 10.17226/13888.
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2CHAPTER 2 STATE OF THE PRACTICE REVIEW OF THE LITERATURE Aesthetics is a branch of philosophy dealing with the theory and perception of beauty and the psychological re- sponses to it. How and why things are perceived as aesthet- ically pleasing is a subjective matter, yet many standards for beauty or aesthetics exist. In terms of highways and their components, Leonhardt(1) discusses the design of a structure as containing many variables that affect aesthetic visual qual- ity. In agreement with many other designers and engineers, the basics of design are function, form, color, and texture. Yet other design characteristics, especially for linear struc- tures such as a concrete barrier or bridge rail, include pro- portion, symmetry, rhythm, repetition, and contrast. Harmo- nious proportion is a valuable component of linear design. The manner in which various parts of the structure (height, width and depth, masses and voids, closed and open surfaces, light and dark created by sun and shadow) relate creates the character of the structure. Tang, in his “Philosophical Basis for Chinese Bridge Aesthetics” describes the concept of “yin and yang” in aesthetics. “The one form has no reality without the other, they are in opposition, comparison, har- mony and succession.”(2) The structures express their unity by opposition as they reflect, complement, and transform one another. Although the aesthetic component of design is the most visible to the user, few guidelines exist. Highway con- struction generally follows the safety and economy rule first. The Federal Highway Administration (FHWA) real- izes that aesthetics and context-sensitive design are impor- tant factors in the design-making process and should be placed “. . . on an equal basis with mobility, safety and eco- nomics.”(3) Safety is the primary concern in highway design, yet safety and aesthetics are not mutually exclusive. “The successful inclusion of highway aesthetics can be achieved for any project by giving consideration to these five “C’s” of design: context, comprehensiveness, cost, contractibility, and community.”(4) The basic philosophical intent of creating highway aes- thetics is to balance the safety and mobility needs of the transportation systems with the human need for a sense of community and aesthetic satisfaction. Both the FHWA and the American Association of State Highway and Transporta- tion Officials (AASHTO) are working to develop the issues of context-sensitive design and the incorporation of this mindset into the highway design process, from geometric design of the roadways to the aesthetic components within and extending beyond the roadway.(5) With the exception of planting design, guidance on when and how to use specific aesthetic elements or treatments in the highway environment is virtually nonexistent. The question of when, where, and why to use color, pattern, textures, art, light- ing, and so forth appears to be generally left to individual or group decision processes and is done in ad hoc manner. The type of criteria used in these decision processes (other than safety and cost issues) is not well established. Experience of the authors suggests that the most common criteria are proba- bly consensus, embodied by the phrase: “Whatever everybody will agree to.” Evidently this is a common occurrence.(6) Many highway design scenarios exist where selection of aesthetic elements and treatments may not pose any significant conflicts or issues. Obviously, however, since the roadway has a potentially hazardous element to its environment, a more clear set of criteria would be desirable to aid designers in their decision making. Two areas of study that offer a framework for roadway aesthetics design are environmental psychology and human factors. Each relates to the other in that both use research from both fields. Environmental psychology seeks to understand and de- scribe humanity’s relationship with the environment. Subsets of this field include environmental cognition and assessment and environmental design. These disciplines study visual per- ception and communication, as well as emotional responses, and how these things affect decision making in real-world environments.(7) This information also applies to deciding what is important in terms of cognition and the prediction of choices or preferences by an individual.(6) A large part of the study in this field attempts to describe this relationship in terms of scenic quality, our preferences for a certain aesthetic, the level of satisfaction we gain from a setting, or our comfort levels during certain activities. Much of the literature involves human responses to the natural environment and how positive experiences can be maximized, particularly in urban settings. Of particular interest in terms of aesthetics is the work done in the areas of driver perception,(8) the visual quality of the driving environment,(9) the effectiveness of signed communi- cation,(10,11) and driver performance related to visibility con- ditions.(12) These and other studies find that as the roadway

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

are typically based on a subjective evaluation or on viewer- preference studies. Why any structure would be considered to be aesthetic in nature is rarely discussed. To be sure, the viewer preference aspect is and will always be an important consideration. But in the potentially dangerous highway roadway, it would be good to know the functional effects of design on driver perception. There is little in the way of tested techniques for designers regarding the use of aesthetic treatments and how these affect the driver’s performance. Except for areas of signage and sig- naling, how a driver perceives other elements in the roadside is poorly understood. Driver simulation studies with real- world verification would provide the needed science to enable designers to have a much better idea of how their designs might affect driver performance and safety. Until such information is available, the single most critical guiding principle should be the delineation of the roadway edge. This implies that: • Colors or shades should provide contrast at least between the base of the barrier and the pavement. • Impact areas of the barrier should be in appropriate con- trast to the background given a specific design speed and the view quality of the potential scene. The following section discusses a viewer preference survey that was performed in this study. The study applies some of the concepts presented in the review of the literature. SURVEY OF STATE DOTS The researchers conducted a telephone survey of state DOTs with the intention of gaining insight into the present practice of aesthetic barrier design. The research team prepared a set of interview questions and tested the questions with three interviews. Based on the results of those interviews, the ques- tions were revised and the rest of the interviews were con- 4 ducted. All 50 states were contacted, but some interviews were unable to be completed. In total, 41 states were interviewed. The questions asked were: • Does your DOT have guidelines on aesthetic treatments for structures? • What type of longitudinal concrete barrier (LCB) does the DOT typically use? • Does your DOT incorporate any type of aesthetic treat- ments into LCBs or bridge rails? • Do you use any aesthetic steel rail or barrier designs? • Do you get requests from the public for aesthetic barriers and rails? • Do you have and use see-through bridge rail designs? • Do you incorporate any use of colors into your LCBs? • Have you used any veneer products such as precast imi- tation stone or brick on LCBs? • Have you used any sandblasted patterning on LCBs? • Does your DOT conduct any testing of barriers or rails? What type? Results? Test levels (TL-1 thru TL-4)? Meet requirements of NCHRP Report 350? • Is there some design you would like to see tested? Of the states that were interviewed, only 22% have guide- lines in place for the aesthetic treatment of roadside struc- tures. The most common type of concrete barrier being used was the New Jersey or F-shape barrier (68%), with the Kansas Corral coming in a distant second (7%). Since the New Jersey and F-shape barriers are essentially identical in appearance, they are considered the same for aesthetic design purposes. Fig- ure 1 shows the breakdown of concrete barriers currently in use. Fifty-nine percent of the surveyed state DOTs do not incor- porate any aesthetic treatments into their concrete barriers, while 39% do. The remaining 2% of respondents were unsure. Thirty-two percent of states use a tube-type steel rail, and 44% stated that they do not use any type of steel rail or bar- rier design. Figure 2 shows the breakdown of steel rails used by the various states. Figure 1. Concrete barriers in use in the United States. Je rs ey, F- sh ap e

5that the most commonly used barrier is the safety shape design. A large number of photographs were received from around the country. An insight into concepts that are being experi- mented with can be gained from a review of these photo- graphs. A few of these that demonstrate the range of ideas in current usage are shown in Figure 4. SURVEY OF U.S. AND INTERNATIONAL CRASH TEST LABORATORIES U.S. Crash Test Laboratories Out of 12 surveys sent via e-mail to U.S. crash test labora- tories, 11 responses were received. Of these, 82% stated that they have not done any work in the area of aesthetic barrier design and/or testing and 18% provided information for use on this project. California DOT (Caltrans) and Midwest Roadside Safety Facility (MwRSF) were the two U.S. labs that provided information as part of the survey. Caltrans provided crash test reports, 16-mm film, and videos for analysis of their research effort to develop design guidelines for single-slope and vertical-face concrete barriers. MwRSF provided crash test reports of aesthetic concrete barriers and steel rails. International Crash Test Laboratories Out of 18 surveys sent via e-mail to international crash test laboratories, 12 responses were received. Of these, 33% stated that they could not provide information due to confi- dentiality issues, 42% have not done any work in this area, and 25% provided information on aesthetic barriers. The labs that provided information were Autostrade, Italy; Transport Research Laboratory (TRL), United Kingdom; and Swedish National Road and Transportation Research Institute (VTI), Sweden. Figure 2. Typical steel rails used by state DOTs. Figure 3. Public requests for aesthetic barriers and rails. Public requests for aesthetic barriers and rails are very common in the states. Forty-six percent of states said that they get a lot of requests from the public for more aestheti- cally pleasing roadside structures. Figure 3 depicts the pub- lic requests. Only 27% of states said that they use see-through bridge rail designs. Thirty-two percent incorporate colors into their concrete barriers, and 24% have used veneer products, such as precast imitation stone or brick, on their concrete barriers. Sandblasted patterning on concrete barriers is not a widely used practice, with only 7% of states using this aesthetic treatment. Eighty-eight percent of states do not conduct any testing on their barriers or rails, and only 41% stated that they would like to see testing performed on specific designs. Most state DOTs are getting increased requests for aes- thetic roadway structures. Some are starting to develop their own guidelines for their designers, but most are relying on existing examples that have proven reliable in other states. There were some comments from respondents to the effect that the only good rail is a smooth rail and that aesthetics should in no way compromise it. This sentiment occurred in a very small number of responses, but may be common among designers in some states. This is reflected in the fact

6Figure 4. State DOT photographs. Photographs provided by Autostrade are shown in Fig- ures 5 and 6. Both installations are types of safety shape con- crete barriers. The first, shown in Figure 5, is used in Rome near the Aurealian ancient walls of the city. In actual appli- cation, flowers and plants are planted in the upper part of the barrier. The second installation, shown in Figure 6, is a vari- ation of a New Jersey border bridge, which allows motorists to view the landscape. TRL also provided photographs of concrete barriers and see-through longitudinal bridge rails. Figure 7 depicts several types of concrete barriers currently used on the United Kingdom Highways Agency (HA) roads. All con- crete safety barriers used on the HA network have a plain, smooth concrete finish of natural color. The majority of all bridge rails take the form of vertical posts with hori- zontal rail members, deeming them see-through. Photo- graphs of several see-through bridge rails are shown in Figure 8. VTI is the only international test laboratory to submit results of NCHRP Report 350 testing done at their facility. The GPLINK concrete road barrier, manufactured by Gun- nar Prefab AB in Mora, Sweden, has FHWA approval for Test Level 3. The FHWA acceptance letter can be accessed at http://safety.fhwa.dot.gov/roadway_dept/road_hardware/ barriers/pdf/b-62.pdf. Photographs of the GPLINK concrete barrier are shown in Figure 9.

7Figure 4. (Continued).

8Figure 4. (Continued).

9Figure 4. (Continued).

10 Figure 4. (Continued).

11 Figure 4. (Continued).

12 Figure 4. (Continued).

13 Figure 5. New Jersey barrier used in Rome. Figure 6. New Jersey border bridge used in Italy.

14 Figure 8. See-through bridge rails used in the United Kingdom. Figure 7. Concrete barriers used in the United Kingdom.

15 Figure 9. GPLINK concrete barrier.

Next: Chapter 3 - Considerations for Developing an Aesthetic Barrier »
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TRB’s National Cooperative Highway Research Program (NCHRP) Report 554: Aesthetic Concrete Barrier Design provides guidance for the aesthetic treatment of concrete safety shape barriers.

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