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An Integrated Approach to Sustainable Roadside Design and Restoration

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3. Design Strategies and Tools

• 3.1 Aesthetics
  • 3.1.1 Introduction
  • 3.1.2 Key Requirements
  • 3.1.3 Trade-offs and Considerations
  • 3.1.4 Recommended Approaches
  • 3.1.5 Aesthetics Checklist

This chapter identifies strategies that reach across all disciplines involved in roadside design. It focuses in detail on four of those disciplines: aesthetics, geotechnical (geotech), hydraulic design, and vegetation. Aesthetics is one that is typically thought of as an overarching objective within a project.

Sustainability solutions within the roadway cross-section, such as pavement materials, are not included in this guidebook nor are detailed solutions for bridges and other structures. Safety is considered an integrated component of all disciplines and is addressed within each.

3.1 Aesthetics

Elements of the roadside aesthetic:

• View Planes
• Roadside Signage
• Retaining Walls
• Snow Fencing
• Rock Fencing
• Clear Zones
• Grading

3.1.1. Introduction

 

Aesthetics, more specifically the roadside aesthetic, is the physical presentation of landforms and the human built environment adjacent to a roadway. Within the context of transportation, aesthetics comprises the visual integration of transportation facilities into the surrounding physical and cultural landscape (Texas DOT, 2009). This relationship can be defined by multiple variables ranging from natural land forms and human-enhanced topography to the design of signage and road-safety elements.

To create an aesthetically pleasing roadside, a balance needs to be struck between the natural world and human-built forms, taking into account the needs of roadway users, the roadway owner, and the preservation or enhancement of the natural and cultural environment. It is important that aesthetics be linked to the functionality of the roadway. Sustainable and aesthetically pleasing roadways not only take into account the preservation of the natural environment but also the economic and social needs of stakeholders (Texas DOT, 2009).

With the growing focus on sustainability comes an emphasis on roadside beautification. Preserving and enhancing the natural environment through the designation of scenic by-ways, highlighting significant cultural resources and creating roadsides that are visually pleasing, has become increasingly important to a diversity of stakeholders (Schauman et al., 1992). As the majority of people interact with natural environments visually via their vehicles, the aesthetics of the roadway become their primary connection to this environment. This focus has not only led to the development of high-quality design elements at the roadside but has also contributed to the fiscal and environmental health of rural communities, enhanced and protected the natural environment, and promoted the importance of natural and historic resources (Figure 3-1). In response to this increased focus, federal and state agencies have begun to develop standards, procedures, and guidelines to address aesthetics of the roadway.

Figure 3-1: Rural roadsides that maximize views

3.1.2 Key Requirements

Detailed regulations for roadside aesthetics are limited. FHWA Title 23, Section 109, of the Code of Federal Regulations requires that "aesthetic or scenic qualities of a place may be taken into account and preserved or enhanced" (Texas DOT, 2009). The FLH Project Design and Development Manual states that the most relevant aesthetics guidance and standards can be found within the National Historic Preservation Act (NHPA) and the Wild and Scenic Rivers Act (WSRA). The NHPA states that designers should work to identify historic elements at the roadside and consider options to minimize adverse effects, including "avoidance, rehabilitation, modified use, marketing and relocation" (NHPA, as amended, 2006). The WSRA of 1966 was implemented to protect rivers that present significant environmental, historic, and scientific value. When designing a road and roadside along a WSR-designated river, designers are required by law to protect the "aesthetic, scenic, historic, archeological, and scientific features" of the river (WSR, 1966). These two acts represent helpful guidance but only pertain to two components of the roadside (historic preservation and protection of rivers). The aesthetics discussion is much broader.

Typically, when roadway engineers begin a design project, the American Association of State Highway and Transportation Officials' (AASHTO) A Policy on Geometric Design of Highways and Streets, 2004 (known as the Green Book), is the first resource consulted. The Green Book outlines the design of roads and highways and provides national roadway design standards. Design guidelines within this guidebook are based on user safety and provide the minimum requirements when designing a road. Aesthetics are not a major focus within the Green Book, thus guidance concerning aesthetics is typically driven by the agency or owner of the roadway in question. On projects where agency guidance is not present, it is the responsibility of the roadway/roadside designer to champion sustainable and context-sensitive aesthetic principles.

Some state DOTs have developed statewide aesthetics guidelines. In their report titled Pattern and Palette of Place: A Landscape and Aesthetics Master Plan for the Nevada State Highway System, the Nevada DOT established a landscape and aesthetics program for the statewide highway system (Multiple Authors, 2002). The report states that context should be one of the most important factors in determining the aesthetic complexion of a roadside. Ohio DOT's Aesthetic Design Guidelines states that the primary goals of the guidelines are to promote a cohesive and uncluttered appearance; consider patterns, colors, textures and relief; and make aesthetics an inherent part of transportation projects. It states that interdisciplinary teams are a crucial part of the design process (Ohio DOT, 2000).

3.1.3 Trade-offs and Considerations

Roadside aesthetics is not a singular design problem. Each discipline and project may have varying goals and objectives. This section defines elements that comprise the rural roadside aesthetic and identifies trade-offs that need to be considered when working with other design disciplines to develop a sustainable roadside.

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Figure 3-2: Roadway vewplanes Visualization showing a complete roadside view (at top) followed by the view with a highlighted foreground, middle ground, and background, respectively.

• Viewplanes: One of the primary aesthetic elements that motorists and passengers experience as they move along a roadway facility is terrain in the foreground, middle ground, and background (Figure 3-2). The sustainable landscape aesthetic is set within the context of the moving motorist. This condition is very different from that of the relatively stationary pedestrian. Thus, when designing the roadside aesthetic, the moving motorists' cone of vision (COV) must be taken into account. Stark contrasts can be identified when comparing a pedestrian COV to a motorist COV. The pedestrian COV typically consists of 60 degrees of direct sight, with the remaining 120 degrees being peripheral. In contrast, the moving motorists' COV is limited by their pace of movement through the landscape. The moving motorists' direct COV is 30 degrees and the remaining 150 degrees make up their peripheral vision (Schauman, et al., 1992). Objects and geological formations that make up the middle and distant views are the most perceptible to the traveler. Within this context, a motorists' COV is wider, allowing viewers to comprehend a broader section of the roadside thus making an aesthetically pleasing roadside important (Figure 3-3) (Texas DOT, 2009).
  
  Elements such as oceans, rivers, hills, and mountains provide many of the most interesting sights when traveling in rural areas (Figure 3-4). These views also serve as way-finding elements, giving topographical clues to distance and location. Highlighting these view plane opportunities helps to create a roadside that is visually appealing, safe, and sustainable. The more interest motorists have when traveling, the more apt they are to stay alert and aware (Schauman, et al., 1992).
  
  Research indicates that a busy roadside that consists of multiple signs and a multitude of travel facilities can distract drivers, leading to increased collisions and accidents (Schauman, et al., 1992). Other studies have shown that a monotonous roadside causes drivers to relax, leading to a loss of concentration and more accidents, negatively impacting the safety of the roadway (Texas DOT, 2009). The development of a balanced rural roadside aesthetic that is interesting but not distracting is imperative in creating safe and sustainable roadsides.

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Figure 3-3: Drivers cone of vision at 55 mph

Figure 3-4: Decorative walls and lighting These add visual interest and help maximize views.

• Vegetation: In some cases, existing vegetation may need to be cleared to maintain view corridors, risking an impact to the overall biodiversity of the area. In other cases, vegetation can help to enhance views by screening undesirable elements (Figure 3-5).

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Figure 3-5: Trees framing views (top) and trees blocking views (bottom)

• Slope design: Areas that require cut and fill need to preserve views. In areas of dramatic topographic change, hillside cuts may be used to not only create a roadway that is safer but also to create more accessible vistas. In contrast, some cut-and-fill sites may need to be adjusted to ensure that existing views are not impeded (Figure 3-6). These trade-offs must be measured against the safety requirements of the roadway.
• Signage: Collaboration with safety professionals is important in creating view opportunities that are noticeable, safe, and sustainable. Signage notifying motorists of an approaching view is important as it promotes driver-awareness of surroundings and advertises the view.
  
  In many cases, historical and cultural signage at the roadside is reflective of the local style. While this may be a contextually appropriate approach, the designs are often developed without studying the lifecycle cost. The trade-off between natural and contextual materials and the lower lifecycle costs of standard materials needs to be studied and weighed in an effort to select the most sustainable solution (Figure 3-7).

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Figure 3-6: A wall detracting from views (left); a terraced wall with reduced scale to accentuate views (right)

Figure 3-7: High quality and contextually appropriate signage

• Retaining walls: Many environments require the use of roadside elements that protect travelers from hazards, such as accumulating snow and steep roadside cuts. To mitigate these hazards, retaining walls and snow fences may be installed. Small enhancements, such as choice of color, materials, and placement, can help to develop walls and fences that are visually appealing, sustainable, and - most importantly - safe.
  
  Retaining walls are utilized on the roadside to protect vehicles from steep slopes. Standard treatments provide adequate safety but, in many cases, are not visually appealing. Multiple aesthetic solutions can help to reduce the impact of retaining walls. Key considerations include lifecycle cost, local materials, and traveler safety (Figure 3-8).

• Snow fences: Snow fences are utilized to keep the travel way clear of snow. Standard designs of snow fences are, in some instances, detrimental to the roadside aesthetic. Typical snow fences are constructed of wood, with a standard life span of 5 to 10 years (Figure 3-9). As an alternative, vegetated snow fences have a substantially longer lifecycle and provide a more pleasant roadside aesthetic.
  
  The initial cost of vegetated snow fences is substantially higher than typical snow fences, in part due to the cost of establishing the vegetation during the first 2 to 3 years. However, the longer life of vegetated snow fences may offset this initial cost. A full lifecycle cost analysis of differing options should be conducted to determine the most financially sustainable option.

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Figure 3-8: Retaining walls enhancing both safety and roadside character

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Figure 3-9: Snow fence treatments

3.1.4 Recommended Approaches

Development of a design approach that is flexible in its response to contextual conditions is imperative in creating specific aesthetic approaches that fit the geological, vegetative, social, and economic conditions of the roadway. This section outlines a suggested approach in developing and designing the aesthetic elements previously discussed.

Step 1: Corridor Principles and Visual Investigation

As with most planning and design processes, the initial scale of work should be at a high, corridor-based level. This area of study is usually defined by the limits of the given project.

However, in some instances, roadside aesthetic principles can be applied to specific historic, geologic, or specially defined regions.

The first step is to define the principles that the design should seek to achieve. Developing a broad "mission" statement at the onset of the project can help to focus detailed design solutions later in the project. In an effort to define the aesthetic principles of the corridor, a visual investigation of the corridor is helpful in understanding the context in which its aesthetics will be defined. An inventory of common features, unique attributes, and historical context can help guide the process. A visual presentation of these qualities can be created to help categorize and illustrate the current conditions of the roadside. These imaging studies can then be delivered to stakeholders in an effort to define the aesthetic principles of the roadway that interventions seek to create, maintain, and protect.

Step 2: Opportunities, Constraints, Weaknesses, and Strengths

Once the visioning process has been completed, the characteristics of the corridor need to be explored in depth. This process should define important elements along the corridor that aesthetic principles can help to enhance, buffer, or create. This process should occur at two scales: corridor-wide and more detailed sections of the corridor.

Corridor-wide Evaluation

A corridor-level view helps determine areas where sustainable aesthetic elements are best utilized and applied. Elements that should be highlighted include land use, population centers, lakes, rivers, open space facilities, and other natural and human-formed features (Figure 3-10). Once opportunities have been documented, designers can begin to define different design districts along the corridor. The aesthetic design of these districts should reflect the contextual environment of the area. Multiple contextual elements can be distinguished at this level of analysis, including:

• View planes
• Vegetation types
• Geological features
• Points of interest
• Proposed roadway engineering designs (cut and fills, walls, guard rails and associated utilities)
• Ancillary utilities

• Jurisdictional boundaries
• Roads
• Railroads
• View sheds
• Population centers
• Recreational amenities

Once this analysis is completed, application of various treatments can be explored.

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Figure 3-10: Example of corridor-wide evaluation

Step 3: Application of Treatments

This section gives an overview of various treatments and strategies to improve corridor aesthetics. These recommendations serve as a starting point. The selection of these will vary by project context and conditions.

Figure 3-11 : Options for preserving the clear zone

• Vegetation: Collaboration with revegetation professionals is required to ensure that threatened and endangered species are not harmed. If revegetation is required, specific species that will not mature to heights that infringe on the view plane should be specified to minimize long-term maintenance.
• Hydrology: Water quality features, culverts, and other hydrological features should be screened or blended into the existing context where possible. Vegetated water quality facilities should use regionally appropriate seed mixes and vegetation to blend into the environment. Culverts should use material that reflects the local geological environment to reduce its visual impact. Other sustainable efforts should be explored, including best management practices (BMP), gravel bottom vegetated water filtration systems, etc.
• Clear zones: Slower road speeds in select areas, increased signage, safety barriers, and adjustment to road alignment can help avoid sensitive and important roadside hazards. FHWA states that agencies have many options to reduce the potential of vehicles leaving the road (Figure 3-11) (FHWA, Highway Safety and Trees, 2006). These options include:
  • Flattening curves
  • Adding signage
  • Improving markings
  • Shielding trees of special significance with guardrail
  • Using smaller trees and shrubs to preserve the clear zone
  • Removing trees
• Signage: The application of signage varies based on the individual needs and context of a roadside. Signage needs to be adequate to enhance safety, accessibility, and educational opportunities while minimizing motorist distraction. Considerations include:
  • Materials should be durable and contextual to the climate of the roadside. Excessive roadside signage is distracting to drivers and impacts roadway safety (Schauman, et al., 1992). Excessive signage also negatively affects the roadside aesthetic. Develop signage standards that convey information in the most efficient manner to create less cluttered roadsides.
  • During the design phase, a signage lifecycle cost analysis should be conducted to determine the overall lifetime cost of upkeep and maintenance.
  • In many cases, information relating to local history, ecology, business, and culture can become outdated, and new signage can be expensive to produce. An alternative to providing physical signage is using intelligent information technologies to convey the information. Smaller signs can be installed at points of interest, directing users to log-on to specific websites using smart devices, such as smart phones or tablet PCs. Another option is to use quick response barcodes, which allow smart phone users to access the information directly. By using these technologies, administrators can update information without having to replace signage at a much higher cost. Drawbacks to using this method may include the increased cost of maintaining a website and, in many rural locations, the lack of mobile and wireless services.
  • Signage information pertaining to points of interest, trail heads, rest stops, and scenic views should be highlighted by placing signs in locations that fall within the traveler's COV. Increased visibility will encourage use of these important amenities and contribute to the local economy.
• Guardrails and retaining walls: The need for safety features along a roadside should be considered within the context of the roadside aesthetic.
  • Where guardrails are required, simple changes in color and material can help to lessen their visual impact on the contextual environment (Figures 3-12 and 3-13).
  • Tiered walls can help to reduce the vertical scale of retaining walls, narrow the size of the roadway footprint, and minimize cut and fill.
  • Vertical walls can detract from the natural aesthetic of the rural environment. The use of materials that blend into the contextual landscape can help to soften the impact of these walls. Shotcrete (specialized concrete that is applied via spray) can be used to create faux retaining walls that match the surrounding geology. Rockery walls can be used to create a clean but rural aesthetic. Textured, colored concrete can be used to break-up the monotony of single color concrete.
  • Terraced walls can help to mitigate the vertical effect of wall structures. Vegetating spaces between walls can also help to screen wall elements from travelers.
  • A lifecycle cost analysis should be undertaken to measure the cost of aesthetic improvements. The location of distributors can affect the total cost of materials.
  • Where cost is not prohibitive, local, sustainable materials should be used to reduce emissions associated with transportation and construction.
• Snow fences: Vegetated snow fences are an alternative to typical snow fencing strategies. A careful analysis of the roadside climate, vegetative norms, and access to water will determine if vegetated snow fences are a viable solution. Intensive maintenance and irrigation is required to develop vegetated snow fences; however, the typical life of a snow fence is five to six times longer than traditional strategies (New York State DOT website).

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Figure 3-12: Retaining wall enhancing surrounding environment

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Figure 3-13: Rock fall mitigation using shotcrete to prevent erosion

3.1.5 Aesthetics Checklist

General

• Develop materials and designs that blend into the environment.
• Specify roadside signs that meet the AASHTO standards but also respond to the local cultural and environmental context.
• Identify important natural features that should be preserved within the clear zone and jointly develop strategies to preserve these features.
• Develop blowing-snow mitigation designs that are safe and visually appealing.

Geotech

• Develop cut and fill designs that ensure preservation of open vistas and view corridors.
• Mitigate the visual effect of cut and fill on the local roadside environment.
• Construct retaining walls that blend into the natural context.
• Ensure that rock fencing has the least amount of visual impact.

Hydrology

• Specify materials and designs that have an extended lifecycle.
• Develop screening strategies for water-quality facilities.

Vegetation

• Determine the impact of vegetative clearing on the local environment.
• Specify plants that will enhance views from the roadway.
• Identify flora to be preserved in the clear zone.
• Specify seed mixes and plantings for water-quality features.
• Revegetate with contextually appropriate plant species.

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