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The landscaping within this highway satisfies both aesthetic
and maintenance criteria
US 33 Bellefontaine
Deciduous trees and grass enhance this rural corridor
Landscape
Landscape elements can improve the appearance of a transportation project. Appropriate landscaping within the highway right-of-way can satisfy safety, aesthetic and maintenance criteria. The landscape architect on the interdisciplinary design team can provide expert guidance. The requirements for safety, planting setbacks, and sight distances can be found in The ODOT Landscape Guidelines in the Location and Design Manual, Volume One.
Plant Material Categories Plant materials must be pollution, drought and salt tolerant. An approved list of tree and shrub species is available in the Ohio section of the Roadside Use of Native Plants, FHWA ep-99-014 or the Ohio State University Extension Office’s “The Native Plants of Ohio” (Bulletin 865, 1998) and on the web at Plant materials are divided into the following categories:
•Ornamental Trees - Use in large masses between tall trees and roadway edge behind required setback distances, in layered arrangement with massed shrubs or groundcovers, to screen and soften bridge and drainage structures.
•Gateway Trees - A different variety can be specified for each community. Gateway trees can be used along ramps behind required setback distances in more formal arrangements. They may also be used as an accent along the roadside to identify community sections.
•Evergreen Trees - Use behind required setback distances when year-round screening or snow fence is desired.
•Large Shrubs - Use behind required setback distances for screening along right-of-way fencing, sound walls, drainage channels.
•Medium Shrubs - Use in large masses beneath trees, to back up deciduous plantings, to fill foreground, or in breaks between groups of trees. Use on flatter slopes.
•Low Shrubs - Use where plant heights of 18 inches or less are required.
•Groundcovers - Use in tighter spaces, or where low, mat-like vegetation is desired.
•Accent Plants - Singular specimens or small groups used for color or form, to accent large plant masses and decision points.
•Perennials - Flowering perennials planted in drifts for accent, to signify decision points and gateways into communities.
•Wildflowers - Use in large open spaces along roadsides and medians to provide seasonal color.
Landforms can be used to screen undesirable views
Plant materials in the highway medians add visual interest and assist
in the reduction of headlight glare.
Landforms intended to be naturalistic should undulate, stop and start,
and vary in elevation along highway corridors.
Points of visual interest can be accentuated with variations along the mainline edge.
Location Guide
General planting guidelines are:
•Planting setbacks and roadside grading must comply with the Landscape Guidelines in the ODOT Location and Design Manual, Volume One. [PG1]
•Graduate heights of plant material with distance away from the primary viewer to open up the roadway space.
•Reserve small groups and more detailed plantings for use where ramps join arterials or other areas of lower traffic speeds.
•Provide access for maintenance purposes.
•Punctuate large masses of trees, shrubs, or groundcovers with appropriate accent plants.
•Avoid staccato, monotonous repetition in plant spacing; vary the number of plants in adjoining groups; vary the distance between accents.
•Incorporate trees and shrubs into a continuous bed to create a bold, visual statement.
•Coordinate the use of color to benefit other colors used throughout the corridor.
•Provide erosion control by establishing root systems that penetrate and anchor soils.
•Evergreens may be planted as a living snow fence with staggered multiple rows. A general rule of thumb is that snow can be deposited on the leeward side of a snow fence over a distance approximately equal to the height of the snow fence. Care can be taken to ensure that the snow fence is planted far enough from the edge of the pavement to prevent snow from being deposited onto the roadway.
Drive monotony can be lessened by creating views. The combination of plant materials and
landforms help screen undesirable views through existing roadside vegetation.
Plant materials along highway edges reduce the amount of light spill- over for the corridor residents.
Outside Edge
The following guidelines are applicable to planting areas along the outside edge of the main roadway and ramps:
•Desirable views can be framed or left unobstructed by using large shrubs in lieu of tall trees to screen the roadway.
•Use of groundcover can be minimal in roadside areas. Use massed shrubs where low plants are desired.
•Planting designs can be in clusters.
•Each continuous mass of trees or shrubs can contain a single species.
•Accent groups can contain from 5 to 15 plants, or as space allows.
•Triangular spacing of massed plants can create a cohesive drift of plant materials.
•Use evergreen plants for visual screening.
•Slopes along roadways can be planted with drifts or masses of ornamental trees and shrubs.
Openings created in existing roadside vegetation provide visual
interest for the motorist.
Encourage areas to be left unmowed.
Typical Highway structure Proposed. Plant materials can tie the highway structures into the landscape.
Plant materials can be used to acknowledge an important intersection.
Interchanges
Interchange areas serve as focal points and provide a gateway for motorists entering and exiting the highway. Where there is excess fill material and adequate right-of-way, landform design for aesthetic purposes is encouraged.
Infield planting may respond differently depending on whether the main line passes under or is elevated over the arterial street. All infields at a single interchange can receive similar or related treatments.
Where the main line passes under the arterial, the infield is sloped in the direction of motorists moving at posted speeds. Planting on this slope can be viewed primarily by highway users and can respond to their rates of movement.
Building Blocks for interchange planting are:
- Strive to integrate bridges with the landscape through the use of medium or large-scale shrubs massed near the abutments.
- Reserve tall trees for use as gateway statements. Infield planting can consist of ornamental trees massed between and above lower plants.
- Aim for a simple, uncluttered design statement that reads well at posted speeds.
- Provide tall trees as vertical accents on infield slopes near the bridge abutments.
- Wildflowers can be a positive feature in interchanges.
Standard
Plant materials can extend the lines of built elements into the landscape. Planting can soften the impact of noise walls on the highway environment.
Building Blocks for infield grading are:
- Consider balance of earthwork in final landform design.
- Ensure that grading is compatible with surface drainage concepts.
- Ensure that landforms do not conflict with roadway grading and safety requirements.
- Use landforms to enhance proposed planting concepts.
Building Blocks for an elevated main line are:
- Plant to minimize visual impacts of the elevated main line on the surrounding community.
- Choose gateway trees to minimize the scale of an elevated roadway and associated structures.
Walls
Planting along noise or combination walls may be different on the highway side as opposed to the community side. Where facing the highway, wall-side planting can be an integral part of the roadside-landscaping concept.
Retaining walls may occur through segments of below-grade highway. Planting may be done in front of these walls to reduce apparent heights or behind them for a cascading effect.
Building Blocks for planting along walls are:
- Plant to minimize wall heights. Shrubs 6 feet tall at the base of a 10-foot wall will leave only 4 feet of wall exposed.
- Avoid use of plants with pale green or grey foliage against the face of walls, unless flowers or leaf texture provides interest.
- Solid planting is not required; plant materials can soften visual impact of walls, not necessarily obscure them.
- Consider the relationship of planting on both sides if taller plants will be visible above the wall at maturity.
- Utilize plants with attractive forms or branching habits when planting in front of taller walls.
- Use vines for accent only, or in very tight spaces that preclude the use of other plants.
Plant materials can tie different elements together to create a unified appearance.
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