CUTS

NOISE BARRIER DESIGN GUIDELINES

Part 3: Prototype Designs

Other parts of the report

Part 1: Table of Contents, Introduction and Background

Part 2: Noise Barrier Design Principles

Part 4: Conclusions, References and Appencicies

Final Report, July, 1990
Prepared by Julie Farnham and Edward Beimborn
Center for Urban Transportation Studies
University of Wisconsin--Milwaukee
Milwaukee, Wisconsin 53201

Sound good/look good.

Design Prototypes


Inventory and Analysis

The first step in the development of prototype designs identifies the opportunities and constraints presented in the community by physical and cultural features. The purpose of the inventory and analysis was to 1) identify regional patterns and features that could potentially impact the visual quality of noise barriers and the freeway corridor; 2) to identify unique cultural, historical or natural features which could be used to set a theme for the design of a noise barrier/landscaping system, and 3) to identify prototypical situations relative to the location and function of noise barriers.

Both research and a windshield visual analysis (video) were conducted to gather information on the following patterns and features on a county-wide scale:

i. Physical (e.g.) topography; vegetation; unique features; and views

ii. Cultural (e.g.) ethnic enclaves; landmarks; former uses ("ghosts")

iii. Land use (e.g.) urban; suburban; rural

Physical Patterns

Analysis was limited to those locations with existing noise barriers and those identified as candidate barrier locations. The most prominent physical features were the existence of mature vegetation in some locations and the visually dominant presence of power lines. Map 1 identifies specific locations along the freeway system where existing vegetation provides a significant asset. In many of those areas the vegetation is within the existing right-of-way (R.O.W.) or near the R.O.W. fence line. A decision must be made as to where (residential or freeway side) a line should be cleared for construction access. While the most appropriate approach will vary by location, a high priority should be given to preserving and utilizing as much of the existing mature vegetation as possible.

Map 1: Physical Patterns



Significant Views

Three locations were identified where future noise barriers could provide visual obstruction of desirable views. These are identified on Map 1 and include:

1) The Milwaukee River at the intersection with Hampton Avenue -- while the current elevation of the freeway bridge spanning the river precludes expansive views, further minimization of this view opportunity should be avoided.

2) The "gate" to the city from the south created by the twin spires of St. Stanislaus Church on the west side of I-94 and the Allen-Bradley clock tower on the east side of I-94. Both of these structures are visual landmarks. Driving north, they provide a gateway to the downtown. Driving south, they mark the transition between the industrial heart of Milwaukee and its traditional neighborhoods.

3) The visually prominent dome of St. Josaphat Basilica. The scale and elegant design of this structure signify its importance as a cultural symbol and landmark.

4) The Milwaukee downtown area is a prominent feature when approached from all directions. The view is especially dramatic from the south on the highrise bridge over the Menomonee Valley.

Cultural Patterns

Cultural patterns and features refer to the location of traditional ethnic neighborhoods along the freeway corridor. This information can be used to extract location specific design characteristics which could be incorporated into the barrier design. One of the objectives of this study is to provide ideas on how to design noise barriers that better reflect the character of the neighborhoods in which they are located. Urban freeways occupy space formerly used for other uses, many of which contributed to the growth and livelihood of the city itself. Remnants of these earlier uses sometimes exist in areas adjacent to freeways.

Map 2: Cultural Patterns



Reflecting these in the design character of noise barriers provides both contextual and historical continuity in the physical environment. Map 2 identifies the historic neighborhoods located along the freeway system. Appendix A provides brief descriptions of each neighborhood and provides insight into significant design qualities which could be incorporated into noise barrier design.

Land Use Patterns

The analysis also revealed patterns of use distinguished by adjacent development as viewed from the roadway. The density and age of development contribute significantly to the character of specific locations. Three general types of residential development were identified as a means to better define an area's character. Map 3 separates the county into zones based on the dominance of particular types of residential development as viewed from the roadway. Three distinct types of development could be observed along with areas that represent transitions between different types.

"Urban" character refers to older residential areas of the city. The freeway cuts through these established neighborhoods resulting in dense residential development immediately adjacent to the corridor. The design character of these areas is associated with man-made geometric forms, hard edges, hard surfaces, vertical lines, and contrast in forms. An appropriate barrier could be constructed of hard materials, using geometric configurations, with a varied top profile and vertical orientation. Plants are used to provide architectural enhancement, shadow patterns, accents, bold forms, and visual contrast.

"Suburban" character refers to areas of lower density and newer housing. The design character is associated with a mixture of geometric, man-made forms, horizontal lines, and amorphic, naturalistic forms. Older suburbs have a more dense, urban character while newer suburbs have retained wooded areas and lower density developments. An appropriate barrier could be constructed of a mix of materials from concrete to wood, using a mix of geometric and curvilinear configurations with a varied top profile. Plants are used primarily to blend, soften and reduce the scale of the wall.

Map 3: Typical Land Use Pattern as Viewed from Roadway.



"Rural" character refers to areas which appear to be undeveloped open space and/or low densities when viewed from the highway. It is unlikely that areas exhibiting actual rural character will be potential candidates for noise barriers. However, some suburban areas, notably Oak Creek and Brookfield, have maintained pockets of "rural" areas. The design character is associated with soft, flowing forms. An appropriate barrier could be constructed of natural materials (wood, stone), using curvilinear configurations and a definite horizontal emphasis. Plants are used to blend the wall with the landscape. Naturalistic planting designs using informal layouts, indigenous plants and muted color schemes would be most appropriate. Table 2 summarizes the relationship between the land use type and design considerations.

TABLE 2
RELATIONSHIP OF LAND USE TYPE TO DESIGN CONSIDERATIONS
Urban Suburban Rural
Orientation vertical horizontal horizontal
Lines angular mixed curvilinear
Balance symmetry mixed asymmetrical
Rhythm regular mixed irregular




Neighborhood Side of Barriers

This section identifies common situations that are created where noise barriers are installed. Ideally, noise barriers should be designed to respond to their specific contexts. As such, the issues of how noise barriers impact both residential neighborhoods and the freeway corridor environment must be given consideration early in the design process. The following examples represent common situations relative to barrier locations. These examples are intended to provide insight into how barriers could be designed to respond to specific locations.

The impact of noise barriers in residential neighborhoods is directly related to their location within the neighborhood. Barriers may be located across the street from residences, at the end of perpendicular local streets, immediately adjacent to private backyards, or next to "left-over" right-of-way.

In situations where barriers are located across the street from residential development, the barrier becomes the edge of the neighborhood. The primary objective should be to retain the traditional scale and character of a residential street (Figure 27). A traditional residential street is commonly characterized by trees lining both sides of the street. The tree canopies create a spatial "envelope" that becomes part of the neighborhood. When a barrier is erected, it often replaces the traditional elements (street trees and houses) that made up one side of the spatial envelope. The barrier becomes the physical edge of the neighborhood, but does not appear as part of the neighborhood because the residential scale of the street edge is lost. Planting street trees along the barrier is a simple way to recreate the spatial envelope of the street and redefine the street as a spatial part of the neighborhood.

Figure 27: Barrier Across Street



In many neighborhoods, existing local streets are terminated by freeways. In these situations, the opportunity exists to make the noise barriers a focal point (Figure 28). This could be achieved in several ways including: 1) using the barrier as a backdrop for outdoor sculpture; 2) installing special ornamental plantings in the focal area; and 3) using the barrier as a canvas for wall graphics which provide directional cues and/or neighborhood identity.

Barriers may also be located immediately adjacent to the backyards of private residences. In some older neighborhoods, where lot sizes are relatively small, barriers are located quite close to the houses. In essence, the barrier becomes the backyard fence. However, because of its height and opacity it appears overpowering and out of scale. In some situations residents have tried to personalize the barrier walls, attaching miscellaneous ornaments to them (e.g. butterflies, flower pots, and flags) (Figure 29).

Planting a hedge of medium to tall shrubs and/or trees along the barrier wall would give it a more residential scale and also discourage people from vandalizing or attaching personal ornaments to the wall. Where possible, the barrier should be located to allow a minimum five foot wide planting strip along the wall within the right-of-way. Where space is extremely limited an arrangement might be negotiated with the abutting residents such that WDOT would provide landscaping on the residents' property, which the residents agree to maintain.

In some areas the alignment of the freeway corridor, as it cut through existing neighborhoods, resulted in the creation of "left-over" parcels of land too small to be used for residential lots. In these situations the opportunity exists to create small, neighborhood "vest-pocket" parks (Figure 30). These might provide amenities such as sitting benches, picnic tables, flower gardens and children's play equipment. However, in creating an unofficial "park" for use by persons other than the property owners, two key issues must be addressed and resolved. First, questions of liability, in case someone were injured while using the "park," would have to be formally worked out with the municipalities, park system, or neighborhood; and secondly, maintenance responsibilities would have to be defined.

Figure 28: Barrier at End of Street

Figure 29: Barrier in Background

Figure 30: "Leftover" Right-of-Way

Freeway Side of Barriers

The installation of noise barriers along urban freeway corridors can significantly affect the driver's experience and the image of the city. If insensitively designed, noise barriers can result in freeway corridors that are both monotonous and anonymous. Design objectives should include: reducing monotony and improving corridor aesthetics; reducing the tunnel effect created by long expanses of identical barrier walls; and capitalizing on opportunities to develop a sense of place within the corridor.

How these objectives are accomplished depends, to some degree, on the physical constraints posed by the highway situation -- whether it is located on fill, at grade, or in a cut situation. The typical urban freeway corridor occupies a 176' wide right-of-way, as a minimum. This typically accommodates six 12' traffic lanes, a 3' center median flanked by two 8' inside shoulders, two 10' outside shoulders, and 20 to 35 feet of open space on either side of the roadway (Figure 31).

Figure 31: Typical Urban Freeway Cross-section



Barriers are located where they will provide maximum noise reduction. Specific barrier locations, relative to the traveled roadway, vary according to the highway situation (Figure 32). In fill situations the barrier is most effective at the edge of the outside shoulder -- as close to the noise source (traffic lanes) as possible. This is also true where the highway is at grade. Where the highway is in cut the barrier is most effective at the top of the cut slope. Obviously, design constraints are most severe in fill situations which offer very limited space for landscaping and/or varying the horizontal configuration of the barrier wall.

Clear zone requirements present another constraint affecting what can be done within the right-of-way. For safety purposes, areas free of obstacles are required next to highways to accommodate errant vehicles. The design speed and traffic volume on urban freeways typically requires that a clear zone of at least 30' be maintained from the edge of the outside traffic lane. In cut situations the distance may be reduced to 16'-20' because the rising back slope functions to slow down and contain errant vehicles. On the other hand, sections of roadway that are identified as "accident prone" may require more space or additional protection devices. While existing stationary objects within the clear zone are left intact if they are protected by barriers or have a break away design, installation of new fixed obstacles within the clear zone is not permitted unless protected. In some situations, low barriers may be located next to the shoulder to contain or redirect errant vehicles.

Figure 32: Roadway Situation and Barrier Location



Important design objectives for barriers are to reduce monotony, reduce the tunnel effect, and to increase aesthetics. It should be noted that actions taken to accommodate one objective may also positively affect another. For example, Figure 33a illustrates several ideas for reducing the tunnel effect by reducing the visual height of the barrier walls. In situations where landscaping is unpractical, variety can be achieved in the barrier design itself. Tilting the wall away from the roadway; changing the wall surface (color, texture, pattern); and stepping the wall back from the roadway can all be used to create variety. These same design ideas may reduce monotony by providing variety.

Figure 33b illustrates several ways landscaping can be used to soften the barrier wall, making it more attractive. These techniques also function to reduce both monotony and the tunnel effect. In situations where space is extremely limited for landscaping, the opportunity might exist to utilize landscaping on the opposite side of the barrier wall to soften the freeway side.

Figure 33: Tunnel Effect and Monotony

a. Reduce visual height of wall b. Soften wall



Designing noise barriers to create a sense of place can be achieved in several ways. The inventory and analysis completed provide information relative to the physical, cultural, and use patterns present throughout Milwaukee County. This information can be used to extract location specific characteristics that can be incorporated into the barrier design. For example, a barrier in a low density suburban area may be designed to look like a residential fence, while a barrier in a dense, urban area may be designed to reflect the residential skyline (Figure 34). Similarly, some areas may have distinguishing historical characteristics that could be incorporated into the barrier design to serve as locational cues.

Figure 34: Urban Rowhouse Motif



Barriers may also be designed in a more literal sense to provide directional and locational cues. Barriers along entry/exit ramps could be designed as gateways to neighborhoods, incorporating location specific forms and symbols. In select areas the wall itself might become a graphic. However, controlling this usage could pose a problem and result in walls becoming billboards. Transparent materials could be used to create windows in walls (Figure 35). Strategically placed, such windows could function as locational cues. In addition, windows could be placed to ensure preservation of significant views (see Map 1). Using clear materials has some disadvantages. The material tends to scratch and get cloudy requiring more frequent replacement. In addition, birds and other flying creatures may be prone to fly into clear panels. However, installing decals of prey birds may reduce this problem.

To assist noise barrier designers in the early stages of the design process, a site inventory analysis checklist was developed (Appendix E). The checklist is intended to be used as a tool to encourage thorough and comprehensive site inventories and analyses. While all of the items listed may not be pertinent to all barrier candidate locations, designers are advised to take them into consideration and develop as many design alternatives as possible. What information may at first appear insignificant could actually contribute significantly to the final design.

Figure 35: Use of Transparent Materials to Create Windows



Prototypical designs were generated to illustrate the application of the design guidelines and ideas presented in previous sections. Five sites along the stretch of I-94 between Ryan Road and downtown Milwaukee were selected to represent prototypical situations. This stretch also acts as a gateway between the airport and downtown. Additionally, a short segment of I-43, where it passes Chambers Street, was selected to represent an example of an "historical ghost."

Before selecting the specific sites a windshield analysis was completed to determine unique characteristics of this corridor section. Map 4 identifies the major observations. The following discussion describes characteristics of the corridor in more detail.

The area between Ryan Road and College Avenue is still quite rural in character. It gives way to newer suburban development as movement proceeds north, toward the airport interchange. A mix of new and older suburban development occurs between the airport interchange and the junction of I-94 with I-894. The junction of the two freeways provides a definite pivot point as development just north of it becomes quite urban in character. North of the junction houses are quite close to the freeway. They are also older and more closely spaced. The two sharp curves in this area provide the opportunity to take advantage of straight-on views of the noise barriers.

North of these curves the freeway cuts through older, established urban neighborhoods. Local landmarks, particularly church spires, are prominent on the skyline. Some locations show evidence of earlier freeway landscaping projects which have grown into mature plantings. Efforts should be taken to minimize destruction of these plantings if new barriers are constructed.

At the intersection of I-94 and Mitchell Street a gateway is formed by the twin spires of St. Stanislaus Church and the Allen-Bradley clock tower. The visual image of a gateway to downtown should be reinforced since just beyond this location, the freeway crosses the Menomonee Valley which opens an expansive view to downtown Milwaukee.

Map 4: Characteristics of I-94 Corridor

as Viewed from the Roadway.

A series of "before" and "after" sketches are were made of several sites along I-94 to illustrate how noise barriers and landscaping can be used to accentuate the characteristics of specific areas in order to create a more aesthetically pleasing and coherent freeway corridor environment. The design intent of each design solution is briefly described below. They are presented in a sequence from the south to represent views a motorist would have while traveling north to the city center. The locations of the sketches are indicated on Map 5.

Site #1 -- Rural Character

This site is located just south of the Rawson Avenue interchange. It is currently relatively undeveloped; however, some low density residential development has occurred. The area is characterized by patches of development interspersed with farm fields, meadows, and woodlands. Historically, this area supported several truck farming and greenhouse operations. Much of its original rural/farm character remains intact.

Noise barriers in this area should be designed to reflect this rural character. Design characteristics of rustic, residential and utilitarian fences could be adapted to the barrier wall design. The barrier wall could be constructed of rough sawn wood, placed in a somewhat loose pattern to resemble grape stakes. The top of the wall (ends of the wood stakes) should be left jagged and uneven. The wall could be placed in a zigzag configuration, reminiscent of a split-rail fence. Landscaping should consist of naturalistic drifts of native grasses and wild flowers. Piles of field stones placed at irregular intervals at the base of the wall would add contrast and visual interest. The extent of landscaping depends on the amount of space available on either side of the wall.

Map 5: Location of Sites for Prototype Designs.



Site #2 -- Suburban

This site is located near the airport. The area is characterized by low to medium density residential development. This stretch of the freeway is in a slight cut, with gently undulating side slopes along its edge. A significant amount of vegetation has been retained along the top of the side slopes, possibly in the backyards of abutting residences. In this situation a primary objective would be to design the barrier to resemble a residential fence. The fence could be designed with panels evenly separated by posts. A strong horizontal texture or pattern on the surface of the panels would help to visually reduce the height of the wall by reinforcing the horizontal line of the landform. A wood barrier would blend nicely into the landscape; however, concrete, brick and metal could also be used to create the same basic result.

Landscaping should consist of informal mass plantings of trees and shrubs on both sides of the barrier. The barrier should appear to meander in and out of "the woods." Consideration should also be given to adding berms so that the height of the wall could be reduced. Berms would also further accentuate the existing land undulations.



Site #3 -- Urban Focal Point

This site is located along the east side of the freeway at the curve just south of Howard Avenue. The sharp curve presents a situation where motorists' views are naturally focused straight ahead to a potential barrier location. The opportunity exists to capitalize on this situation and create focal points.

This site is located in the Bayview neighborhood which began as an iron and steel company town. Barriers in this area could be constructed of metal to acknowledge the local historical roots. Designs made of metal tracery work could provide focal interest. The design solution proposed suggests attaching decorative metal tracery screens to smooth metal wall panels. Some space should be left between the tracery screen and the wall panel to create depth and shadow patterns. In addition, the wall panel should be light in color to ensure that

shadow patterns are visible. To retain their focal impact and contextual uniqueness, decorative panels of this type should be used sparingly. Adjacent wall sections should be rather simple to avoid visual distraction and confusion. Dark colored adjacent wall sections would be appropriate to provide contrast.

No landscaping is required along the decorative panels, since the barrier itself is visually attractive. Landscaping along the adjacent wall sections should also be simple. In this example, an existing row of trees was retained on the freeway side of the barrier. The area consists of a dense urban residential development. The row of trees lends a simple, urban character -- resembling a residential streetscape.

Site #4 -- Urban Neighborhood

This site is located near Lincoln Avenue in a densely developed, old urban neighborhood. The site contains two significant attributes: a dense row of healthy, mature vegetation, and a prominent local landmark, the dome of St. Josaphat Basilica, an historic church, as a backdrop. The barrier should be designed to accommodate both of these assets. The solution proposed is relatively simple in design. The wall should be designed to have a finished, more refined, urban character. Pillars could be placed at regular intervals between spans of wall panels. In this example, the shape of the pillar is designed to reflect the Basilica's dome. They are light colored to provide contrast. The wall panels should be relatively dark in color, so they visually recede into the landscape plantings. A contrasting (light colored) cap provides a finishing touch to the top of the wall.

Special care should be used when siting and constructing the barrier in order to save and utilize as much of the existing vegetation as possible. Ideally, the barrier should appear to weave through the landscaping. Some additional landscaping might be necessary to blend the overall design into the existing landscape.



Site #5 -- Urban Gateway

This site is located near the downtown along the Mitchell Street interchange. A sense of gateway is created by two visually prominent vertical structures located on either side of the roadway. The twin spires of St. Stanislaus Church and the Allen-Bradley clock tower are prominent Milwaukee landmarks located along the seam where the industrial heart of the city meets its oldest residential neighborhoods. Because of their visual prominence and juxtaposition to each other, and to downtown, they create a gateway signaling either the entrance to or exit from the heart of the city (downtown).

A noise barrier on this site could be designed to reinforce the gateway image. As proposed, the top profile of the walls are stepped to emphasize an upward movement. The walls are tied to the existing bridge structure by vertical pillars. These pillars create a more literal gateway, making reference to the implied gateway created by the two prominent buildings in the background. Concrete wall panels are used to express the very urban character of the site. Vertical posts between wall panels accentuate the upward movement toward the pillars and the verticality of the surrounding architecture. The vertical elements, end pillars and panel posts, should be darker in color than the wall panels to make them visually dominant.

The landscape treatment suggested consists of vines planted on the residential side of the wall that are allowed to cascade over the top, softening the horizontal line of the wall panels. This wall could also be designed to incorporate a planter along the top which could be planted with brightly colored annual flowers. This would give reference to the landscaped boulevards which have become a Milwaukee trademark.



Site #6 -- Historical Ghost

This site is located where I-94 crosses Chambers Street. It is the former site of Borchert Field which served as the major athletic field for Milwaukee baseball teams during the first

half of the century until the opening of Milwaukee County Stadium in 1953. In the same year, Borchert Field was demolished to make way for construction of I-43. To reflect this cultural relic, the barrier walls could be designed using a baseball theme.

To avoid being overly sentimental (and distractive), the design should be simple and uncluttered. The solution proposed involves the integration of a backstop into the barrier on the west side of the freeway. Home base would be constructed of an appropriately shaped slab of white concrete or marble. The dimensions of the base would have to be exaggerated somewhat to increase its visibility. The base would be placed within a bed of reddish colored gravel to provide heightened contrast. The existing slope of the cut bank could be utilized to make the base more visible by tilting it toward the roadway.

Borchert Field stadium was a wooden structure. Similarly, the barrier walls should be constructed of wood boards, preferably with a weathered finish, placed vertically, side by side. The wooden walls should only extend about 200' beyond the backstop, being of equal length on both sides of the freeway, alluding to the size of a baseball stadium. Numbers stenciled on the east side barrier signify field length. Vertical poles symbolize foul line markers. A change of materials would clearly signal that this area is distinct. The design proposed suggests that the barrier material change should not occur abruptly. Instead, over the distance of three wall panel segments the materials could be integrated by attaching wood panels, in graduating heights, forming a stepped pattern, to the surface of the adjacent barrier. Concrete would be an appropriate choice of material for the adjacent barrier because it would provide color contrast and could be given a vertical surface texture to complement the wood barrier design.

Landscaping on the freeway side would be minimal. Vines could be planted to grow on or over the wall. Conceptually, the cut slope should be planted with turf grass. At the point where the barrier material changes, the landscape treatment should also change. The area immediately adjacent to the turf should be planted with a taller ground cover to clearly delineate the edge of the historic "ball field."

Part 4: Conclusions, references and appendicies