AESTHETICS

Often, a detailed study is required to address the question of aesthetics. Alternative systems can be compared, with sketches, renderings, plan drawings, and other visual aids prepared to assist in the process. A multidiscipline team approach is desirable, including design engineers, planners, landscape architects, and environmental personnel. Public input to the selection system helps achieve acceptance of the final system. Designers should be concerned with the visual impact from both the driver’s side and the land user’s side of the wall.

Some of the important aspects of aesthetics include scale relationship, relationship to environmental setting, line form, color, and texture. A high barrier alongside a row of single-story houses is not desirable, nor is one placed so close to the residences that unwanted shadows are created. A rule of thumb is to locate the barrier at a distance of atleast 4 times its height from the residences. Barriers higher than 16 ft (5 m) should be critically evaluated for potential unsightly impact.

Evergreens and other plantings are often used with noise barriers to enhance appearance. Vines, encouraged to grow up the posts and across the top, have been appreciated by the public. Most agree that walls with extensive landscaping are the most visually appealing.

When the elevation changes along the length of the wall, it is generally considered more pleasing to step the wall rather than to taper it. Ordinarily, the wall will be con­structed vertically. There has been some use of walls that have the top tilted away from the roadway in an effort to reduce echo, but such walls tend to give the appear­ance of instability when viewed from the back side.

On concrete panel walls, etc., it is necessary to place steel brackets or similar devices at the top of the joints between panels to hold the panels in alignment. A slight horizontal difference of 1 or 2 in (25 or 50 mm) between the tops of adjacent panels may give the illusion that some panels are in distress. This illusion is greatly enhanced by sun shadow lines that, under certain conditions, cast increasing shadows as one looks along the panels. For walls already in place, maintenance forces can tilt panels back in place with a backhoe or similar equipment and add the brackets.

If a barrier is located in an area with dominant architectural features, this should be considered in the selection of barrier material, texture, and color. On the other hand, if located near dominant roadside features such as bridges, there should be an effort to create a strong visual relationship to such features.

In most cases, there should be some consistency in color and surface treatment. For example, some agencies use color scheme and architectural treatment to distinguish between particular corridors.

In general, barriers with darker colors are preferred to lighter ones because they tend to blend better with the background. Although it is usually desirable to avoid visual dominance, murals painted on noise barriers have been well received in some urban regions. The murals tend to discourage graffiti, and in some cases, youth groups have been active in restoring murals defaced by graffiti.

With concrete barriers, a textured appearance can give the effect of shadows and is often considered desirable. Deep textures are more effective than shallow ones. Such treatments can be achieved by a raking technique on the surface of the newly placed concrete. Colors can be obtained with additions to the mix, or by applying a pigmented sealer after the barrier is constructed. The latter technique helps take care of small color variations between panels and minor field problems. Also, coatings can aid in removing graffiti and restoring the intended surface.

For a pleasing visual effect, as well as for safety and acoustic considerations, barriers should not begin or end abruptly. To achieve this, they may be stepped down, flared, or tied into an earth berm, a hillside, a bridge abutment, or another feature. Tapering or stepping is particularly desirable where the height of the barrier exceeds 6 ft (1.8 mm).

Views of several noise walls are shown in Figs. 9.2 through 9.5 to illustrate some of the effects that can be achieved. Figure 9.2 shows concrete-block construction and deep texturing with vertical grooves. The wall is stepped rather than tapered in height. Figure 9.3 shows timber tongue-in-groove construction, with a natural finish and a stepped height. In Fig. 9.4, the alignment of the timber barrier has been changed to a buttress configuration, and extensive plantings have been added. A much different effect has been obtained with concrete post construction, in Fig. 9.5, where the light posts make a distinct contrast with the darker timber.

Making use of variant sun shadow lines on tops of concrete posts yields a changing view of the posts and wall as the sun direction changes during the day. Morning and afternoon shadow lines are greater and thus tend to make aesthetically pleasing wall tops. Also, early morning and late evening sun glare is reduced by north-south noise walls.