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Section 5: Aesthetics of Transportation System Elements

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An aesthetically pleasing setting is one in which each element of the design is in harmony with all others. This simple principle is the foundation of aesthetic design for transportation facilities. A transportation corridor is a complex composition of functional elements, each designed to meet a specific task. To meet the goal of visual harmony the design characteristics of individual elements must be coordinated to provide a clear sense of order, clarity, and continuity.

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Visual Design Elements

The following visual design elements collectively establish the architectural and visual framework of transportation facilities and most directly affect perceptions of the facility and the surrounding environment:

TxDOT districts are encouraged to develop corridor-specific plans to coordinate the aesthetic properties of materials, colors, textures, patterns, and form, particularly within key urban corridors of the district. The vehicles for accomplishing this are the Landscape and Aesthetics Assessment and the Landscape and Aesthetics Master Plan.

Material. With the possible exception of landform, the materials used to build a transportation facility exercise the greatest impact on the aesthetic and visual quality. The materials palette of transportation is broad and includes common structural materials such as concrete, steel, asphalt, rock, and soil. However, the palette also includes plant materials, which are used for erosion control, slope stabilization, and reforestation as well as contributing to the aesthetic quality of the facility.

Materials generally possess native design traits that cover all of the other design elements of color, texture, pattern, and form. Therefore the selection of a material often sets the character of the other design elements. For this reason material selection should always be done with some consideration of the aesthetic properties and how they will fit into the adjacent landscape.

Color. Color is generally associated with a material. Concrete for example has a native color of mottled warm gray to off white. This color is not particularly objectionable but when the dominant material of a transportation facility is concrete such as a typical urban freeway, it becomes visually dull and monotonous. Color can be added using surface finishes.

Texture. Texture is the apparent roughness or smoothness of a surface. Texture can be an important element in creating visual variety within a transportation corridor. Some materials such as glass or steel have a smooth texture that is difficult to change. However, materials such as concrete can be easily textured by manipulating how it is placed and finished. The use of texture is often a good alternative when the use of color is not desirable or cost effective.

Pattern. Pattern is usually the result of a finishing technique or the placement of modular units. Some common elements of the transportation design palette that generally have a strong visual pattern that will impact the visual quality are retaining walls, bridge and guard rails, modular pavements, and some illumination hardware. When materials have strong pattern characteristics they should be coordinated with other elements of the corridor to achieve visual harmony.

Form. Most structural elements of a transportation corridor have distinct form characteristics. In general transportation facilities that move vehicles have very sinuous geometries as opposed to the more rigid geometric forms of the built environment. These flowing forms tend to be visually compatible with the natural landscape. In urban settings the curvilinear geometry of bridges and transportation rights-of-way do not fit easily into the rigid grid-like form of the city. The mismatch in geometry often results in unanticipated or undesirable edge conditions where the two geometric types meet.

In the ground plane the sinuous curves of horizontal alignments needed for safety and mobility result in a ragged patchwork of small, usually triangular parcels. These are often too small to use effectively and can be very difficult to maintain. Designers should be conscious of these conditions and avoid the creation of maintenance problems. Selling or trading the land to adjacent properties when there is no need for the right-of-way is one of the most practical solutions.

In vertical plane embankments, walls and bridge supports often create shaded areas that tend to collect trash and become unsightly. Careful consideration of what happens under structures and their proximity to adjacent properties is critical. Since the areas under bridges do not receive direct sun, vegetation is seldom an appropriate ground surface treatment.

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