How Landscape Architects Contribute to
Context Sensitive Design of Thoroughfares

James C. Gamble
Land Design Collaborative, Inc.

Article appeared in the April 2006 Transportation Design
Issue of elevation:, newsletter of the Illinois chapter
of the American Society of Landscape Architects

Before the availability of reliable automobiles and a highway system, suburban development followed the commuter rail lines as they were extended to undeveloped lands beyond the city. Following World War II, automobiles allowed access to more remote suburban areas not served by the commuter railroads. Larger and more remote properties were accessible by automobiles, creating new communities far from the central city. The state and county highways, supported by federal funds, became the backbone of the suburban roadway system and an integral part of an interstate highway system.

To provide better linkages between these new remote suburban communities and the central city, roads were widened, and new arterial roadways, expressways, and toll ways were built. The rural roadway network was designed for safe and efficient travel at speeds and capacities far below what were needed as suburban growth increased. As roads with greater traffic capacity are needed, new wider roads are built and old roads widened to meet the demand for traffic lanes.

Landscape architects are effective roadway design team members in the critical preliminary design phase. Their skills in design are needed to reduce the negative impact of the roadway widening by making it fit in the context of the site while maintaining the image and qualify of life of the community.

Today, the state highway is a continuous thoroughfare with communities along it like beads on a string. As suburban communities develop they wish to distinguish themselves from their neighbors. Communities use land use, zoning, streetscape enhancements and landscape requirements to affect the design and aesthetic character of the roadways bisecting their downtowns and commercial areas. The challenge of creating a downtown identity for a suburban community is problematic, since many of the main roads are under state or county jurisdiction and were developed to move traffic at a regional level, which often conflicts with the lifestyle of the local community. Too often these roads bisect downtowns and degrade local vehicle circulation and pedestrian use.

There are few places for pedestrians to cross suburban arterial roads safely. Roadway design speeds, multiple through lanes, dual left turn lanes and large corner radii widen roadways, consume medians and compromise pedestrian waiting areas. As roads widen, it reduces "green-time" available for crossing, making it impossible for people to cross at grade without being in a car. Grade separated pedestrian crossings are an option, but they are expensive and often unused, and in some cases there is not enough room.

Typical suburban arterial roadway

Typical surburban arterial roadway 

IDOT Design Process

Historically, the Illinois Department of Transportation (IDOT) has allowed few deviations from its standard design requirements and usually the costs for any deviations are borne by the community. The IDOT roadway design process, is basically broken into three very structured phases:

  1. Phase I Design: The phase when planning and preliminary design occurs
  2. Phase II Design: The phase when Construction Design of features occurs
  3. Phase III Design: The phase when construction of the project occurs

Currently landscape architects do contribute in the design of roads, particularly in the areas of landscape planting design during Phases II and Phase III with the preparation of landscape construction plans for plantings in the right of way. Although developing a planting plan for the right of way is important, it runs the risk of only covering up problems that should have been addressed earlier in the process.

Landscape Architects' Involvement in Roadway Design

A valuable time for landscape architects to be included in the design process is during the Phase I design. Involvement of a landscape architect should be required in the IDOT highway design process starting in Phase I Design. Landscape architects should work as equal partners on the engineering design team to develop design alternatives for the engineering concepts where "design by the book" compromises the aesthetic values of the community. There are a number of behavioral and contextual considerations that should be included in the design of roadways that landscape architects have the ability to provide. Important relationships exist between travel speeds, the design of the right of way, and the perception of car occupants. The accompanying illustration shows the effects of speed on a driverís cone of vision and ability to process information.

  • As Speed Increases, Peripheral Vision Diminishes: At 25 mph the eye sees 100 degrees horizontally; at 60 mph itís reduced to 40 degrees.
  • As Speed Increases, Concentration Increases: Planes perpendicular to the road are prominent; parallel ones are not.
  • As Speed Increases, the Point of Concentration Recedes: The driverís eye focusing point at 25 mph is 600 feet ahead where at 65 mph it is 2000 feet.
  • As Speed Increases, Foreground Detail Begins to Fade: At 40 mph the nearest point of clear vision is 80 feet, at 60 mph its 110 feet. In fact, vision is really only in focus between 110 and 1400 feet at 60 mph, a distance traveled in 15 seconds.
  • As Speed Increases, Space Perception Becomes Impaired: Without visual clues such as trees along the highway, it is difficult for drivers to judge speed and distance.

Communities that have had the most success in achieving modifications to IDOT plans have engaged their own design consultant to develop design enhancements prior to or during IDOTís development of Phase I Engineering Plans. Land Design Collaborative (LDC) has provided services to communities for enhancements to roads, bridges, and downtown streetscape improvements on IDOT initiated projects. In St. Charles, Illinois, at the Cityís request, LDC developed Phase I and Phase II designs for the Main Street (Route 64) bridge which did not follow the IDOT standard bridge, but in fact retained the graceful look of the historic bridge and incorporated open steel railings in lieu of solid concrete ones to allow views of the Fox River from passing cars.

  Relationship between focusing distance, angle of vision and distance of foreground detail at speeds of 40 mph, 50 mph and 60 mph

Relationship between focusing distance, angle
of vision and distance of foreground detail
at speeds of 40 mph, 50 mph and 60 mph
Click to see enlarged version

LDC also developed design recommendations for the Borman Expressway (17 miles of I-80) that would reduce negative highway impacts on adjacent homes while reducing effects of chaos and monotony on drivers caused by the existing right of way conditions.

Landscape architects are highly qualified to address the planting requirements of roadway design. There needs to be a routine that includes the landscape architect to address key issues during right-of-way design, such as:

The Main Street bridge project in St. Charles received a Presdent's Award from ILASLA

The Main Street bridge project in St. Charles received a President's Award from ILASLA 

Illinois Adopts Context Sensitive Design Principles

Rights of way and travel lanes have increased; what seemed adequate by yesterdayís standards are too narrow and need to be widened to increase capacity and safety and reduce congestion. The older and narrower state routes are clogged with traffic and constrain traffic flow creating bottlenecks between old suburbs and new remote suburban communities. Often, state routes divide older suburban downtown commercial areas that grew with the increased traffic along the old road and, when widened, sidewalks and on-street parking are decimated.

Context Sensitive Solutions in Highway Design is intended to mitigate negative impacts of highway improvements and this federal program has been adopted by the State of Illinois. It creates an opportunity for landscape architects to become part of the engineering design process and contribute to the success of the program. Landscape Architects must be proactive in the pursuit of meaningful involvement in roadway corridor design and be allowed to contribute. This becomes most challenging when these contributions are perceived to be superfluous and in exclusive practice areas of other design professionals.