Glossary of Terms

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Alternatives to be Carried Forward
The second Concurrence Point in the NEPA/404 Process. This is where the cooperating agencies agree on which alternatives merit detailed analysis.

Arterial streets provide high mobility with limited land access allowed. Intersections are spaced in 0.5 to 2 mile intervals in an attempt to increase mobility.

Average Daily Traffic (ADT)
The calculation of average traffic volumes in both directions of travel in a time period greater than one day and less than one year and divided by the number of days in that time period.

The maximum number of vehicles which can reasonably be expected to traverse a point of uniform section of a road during a given time period under prevailing roadway, traffic, and traffic control conditions. The time period most often used for analysis is 15 minutes.

Chicago Metropolitan Agency for Planning (CMAP)
The official regional planning organization for the northeastern Illinois counties of Cook, DuPage, Kane, Kendall, Lake, McHenry, and Will. CMAP developed and now guides the implementation of GO TO 2040, metropolitan Chicago’s first comprehensive regional plan in more than 100 years.

Collector streets collect and distribute traffic between local streets and arterials by providing limited mobility in combination with land access. Intersections on collector streets are spaced at 0.5 mile intervals or less.

Written determination by a regulatory agency that information to date is adequate to agree that the project can be advanced to the next stage of project development. Agencies agree not to revisit the previous process steps unless conditions change.

Concurrence Points
A point within the NEPA process where the transportation agency requests formal concurrence.

Concurrent NEPA/404 Processes
In a May 1, 1992 agreement, the U.S. Department of Transportation, the Department of the Army, and the U.S. Environmental Protection Agency adopted the document “Applying the Section 404 Permit Process to Federal-aid Highway Projects.” This document endorsed methods to integrate compliance with the National Environmental Policy Act (NEPA) and the requirements of Section 404 of the Clean Water Act.

In a March, 1994 agreement, the Federal Highway Administration, the U.S. Army Corps of Engineers, the U.S. Environmental Protection Agency, and the U.S. Fish and Wildlife Service adopted the Implementation Guidance document entitled “Concurrent NEPA/404 Processes for Transportation Projects.” The intent of this document was to improve cooperation and efficiency of governmental operations, expedite construction of necessary transportation projects, and protect and enhance the waters of the United States and wetlands.

Cooperating Agencies
Any Federal agency other than a lead agency which has jurisdiction by law or special expertise with respect to any environmental impact involved in a proposal (or a reasonable alternative) for legislation or other major Federal action significantly affecting the quality of the human environment. A State or local agency of similar qualifications may, by agreement with the lead agency, become a cooperating agency. Following is a list of typical Cooperating Agencies:

  • U.S. Environmental Protection Agency (USEPA)
  • U.S. Fish and Wildlife Service (USFWS)
  • Federal Highway Administration (FHWA)
  • U.S. Army Corps of Engineers (USACE)
  • Illinois Department of Transportation (IDOT)
  • State Resource/Regulatory Agencies
  • Illinois Environmental Protection Agency
  • Illinois Natural History Survey
  • Illinois State Geological Survey
  • Illinois State Water Survey
  • Illinois Department of Natural Resources
  • Illinois Department of Agriculture
  • Illinois Historic Preservation Agency
  • Natural Resources Conservation Service
  • Illinois Nature Preserves Commission

The primary performance measure on interrupted flow facilities, especially at signalized intersections. For this element, average stopped-time delay is measured, which is expressed in seconds per vehicle.

Design Hourly Volume(DHV)
The traffic volume for the design hour in the peak direction of flow.

Design Year
Roadway Improvement projects are typically designed for a 20 year planning horizon. The proposed improvement needs to accommodate traffic projections 20 years into the future.

Environmental Class of Action Determination (ECAD)
The categorization of the significance of the environmental impact of a proposed action and the corresponding level of environmental documentation required.

Environmental Impact Statement (EIS)
A detailed written statement, prepared for major Federal actions significantly affecting the quality of the human environment, which discusses the environmental impact of the proposed action; any adverse environmental effects which cannot be avoided should the proposal be implemented; alternatives to the proposed action; the relationship between local short-term uses of man’s environment and the maintenance and enhancement of long-term productivity; and any irreversible and irretrievable commitments of resources which should be involved in the proposed action should it be implemented.

Environmental Studies
The investigations of potential environmental impacts to determine the environmental process to be followed and to assist in the preparation of the environmental document.

Expressways provide maximum mobility with no land access. Expressways are divided highways which are designed for high speed travel. Access to an expressway occurs through an interchange.

Federally Funded/Regulated
Refers to the involvement of Federal funds and/or jurisdictional authority by any Federal agency for a proposed action.

Finding of No Significant Impact (FONSI)
A document by a Federal Agency briefly presenting the reasons why an action, not otherwise excluded, will not have a significant impact on the human environment and for which an environmental impact statement will not be prepared.

Functional Classification
The function of every street is to provide some combination of traffic movement and access to adjacent land. The conflicting goals between these mobility and land access functions inherently result in traffic flow and safety problems as well as livability impacts on adjacent land uses. General functional classifications are Expressway, Arterial, Collector, and Local Street.

GO TO 2040
Chicago’s first comprehensive regional plan in more than 100 years, which was developed by CMAP to address anticipated population growth of more than 2 million new residents. GO TO 2040 establishes coordinated strategies that help the region’s 284 communities address transportation, housing, economic development, open space, the environment, and other quality-of-life issues.

Highway Capacity
The capacity of a roadway is defined as the maximum hourly rate at which vehicles can reasonably be expected to travel through an intersection or section of roadway during a given time period. Some factors having a primary influence on the capacity of an intersection or roadway segment are: the number and width of lanes, other geometric considerations (sight distance, approach grades, turning radii), vehicle mix, turning percentages and signal timings.

Hine’s Emerald Dragonfly
The Hine’s emerald dragonfly was added to the U.S. List of Endangered and Threatened Wildlife and Plants on January 26, 1995 as an endangered species. This dragonfly has bright emerald-green eyes and a metallic green body, with yellow stripes on its sides. Its body is about 2.5 inches long; its wingspan reaches about 3.3 inches. The Hine’s emerald dragonfly lives in calcareous (high in calcium carbonate) spring-fed marshes and sedge meadows overlaying dolomite bedrock. Breeding populations are now known to occur in or near the Des Plaines River Valley.


An interchange is a system of interconnecting roadways in conjunction with one or more grade separations that provides for the movement of traffic between two or more roadways or highways on different levels.

An intersection is defined as the general area where two or more roadways join or cross, including the roadway and roadside facilities for traffic movements within the area.

Lead Agency
The agency or agencies preparing or having assumed primary responsibility for preparing the environmental document.

Level of Service (LOS)
A qualitative concept which has been developed to characterize degrees of congestion as perceived by motorists. Letter designations, A through F, have been correlated to quantitative measures based on the amount of delay experienced at an intersection. Level A represents the best conditions and level F the worst.

When designing new or rehabilitated highways in the Chicago region, the Illinois Department of Transportation estimates future traffic volumes (generally 20 years into the future) and strives to design intersections to operate at Level of Service “D” with Design Year traffic.

Local Streets
Local streets provide maximum land access and minimum mobility. Access to a local street is on an as needed basis to allow property owners access to a transportation facility.

A permissive condition allowing individual judgement and discretion in the evaluation and decision-making. If the term is used in specifying a procedure, that procedure is optional.

Metropolitan Planning Organization (MPO)
The Federal government and local officials designate local planning agencies to assure that projects undertaken with Federal funds are consistent with the regional transportation and land use planning in the area. For northeastern Illinois the MPO is the Chicago Metropolitan Agency for Planning (CMAP).

Mitigation includes the following items:

  • Avoiding the impact altogether by not taking a certain action or parts of an action.
  • Minimizing impacts by limiting the degree or magnitude of the action and its implementation.
  • Rectifying the impact of repairing, rehabilitating, or restoring the affected environment.
  • Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action.
  • Compensating for the impact by replacing or providing substitute resources or environments.

Mitigation Measures
Activities identified in the environmental process intended to lessen the severity of any unavoidable environmental impacts precipitated by the proposed action.

National Environmental Policy Act of 1969 (NEPA)
Landmark environmental legislation which set forth a national policy for and is the nation’s legal basis for ensuring the protection and enhancement of the quality of the human environment. As such, it is the foundation of more specific environmental controls on the action of Federal agencies and other agencies who use Federal funds or engage in Federally regulated activities. This Act and subsequent laws established the format and requirements for Environmental Impact Statements, Environmental Assessments, Categorical Exclusions, etc.

Provides bus transportation primarily in the suburban areas outside of the City of Chicago.

Peak Hour
The single hour in the day during which the maximum traffic volume occurs on a particular roadway. Peak hours are further classified as an A.M. peak hour, a P.M. peak hour, or a weekend peak hour.

For purpose of the Federal flood plan regulations, means capable of being done within reasonable natural, social or economic constraints.

Purpose of and Need for Action
The first Concurrence Point in the NEPA/404 Process. The Purpose and Need identifies and describes the proposed action and the transportation problem which it is intended to address.

Regional Planning Board (RPB)
The Regional Planning Board (RPB) was created on August 8, 2005. The RPB combines the previously separate transportation and land-use planning agencies for northeastern Illinois into a single entity designed to integrate planning for land use and transportation in the seven-county region.

Property owned by a government agency used for the construction of public facilities like a roadway or a bridge.

An early and open process for determining the scope of issues to be addressed in Environmental Impact Statements or Environmental Assessments and for identifying potentially significant issues related to the proposed action. Scoping is intended to focus the study effort on issues that are significant and avoid the collection of needless detailed information on insignificant issues.

Section 4(f) Land
Land protected under 49 USC 303 (Section 4(f) of the USDOT Act of 1966); i.e. any significant publicly owned park, recreational area, or wildlife and waterfowl refuge or a historic site of national, State, or local significance. Significance is determined by the Federal, State, or local officials having jurisdiction over the park, recreational area, refuge or site. The term “historic site” includes both historic and prehistoric archaeological sites determined important for preservation in place.

Section 6(f) Lands
Lands which had Land and Water Conservation (LAWCON) funds involved in their purchase or development.

Section 404 Permit
Beginning in 1899 the U.S. Army Corps of Engineers was given regulatory function over public waterways. Public waterways at that time included rivers, harbors and other bodies of water which were navigable. In 1972 the Federal Water Pollution Control Act expanded the Corps regulatory function to include oversight of the “discharge of dredge material”. Additionally, a definition of the “Waters of the United States” was also included in this law which expanded the Corps jurisdiction to include tributaries of navigable waters. In response to Section 404 of this 1972 law, a Federal permit process was established which requires that if a project will impact the Waters of the United States, all practical alternatives which avoid and minimize impacts must be evaluated.

Selected Alternative
The third Concurrence Point in the NEPA/404 Process. Concurrence means that the agencies agree that the selected alternative is the least damaging practicable alternative available to the applicant. This concurrence will allow the applicant to move forward with the final design.

Shall, Must
A mandatory condition. Users are obligated to adhere to the recommendations and applications presented in this context or to perform the evaluation indicated. If these terms are used in specifying a procedure, that procedure is mandatory.

An advisory condition. Users are strongly encouraged to follow the criteria and guidance presented in this context. If these terms are used in specifying procedures, that procedure is recommended. Deviations from the specified procedure should be justified.

Strategic Regional Arterial (SRA)
The Strategic Regional Arterial system is a network of approximately 1,500 miles of existing roads in northeastern Illinois. The system includes routes in Cook, DuPage, Kane, Lake, McHenry, and Will Counties. Creation of the SRA system is a major component of Operation GreenLight, an eight-point plan to deal with urban congestion and improve regional mobility. The plan was developed by IDOT in cooperation with the Illinois State Toll Highway Authority (ISTHA), CATS, NIPC and the Regional Transportation Authority (RTA). The SRA system, which was first designated as part of the 2010 Transportation System Development Plan adopted by regional planning agencies and continues as a component of the 2020 Regional Transportation Plan, is intended to supplement the existing and proposed expressway facilities by accommodating a significant portion of long-distance, high volume automobile and commercial vehicle traffic in the region.

Transportation Corridor Committee (TCC)
A group of 14 community leaders from the Will County Area who have been commissioned to study the development of a new river crossing of the Des Plaines River, and the development of the Caton Farm Road – Bruce Road corridor. Go to “Project Team” for list of the TCC members.

A controlled access roadway (maximum mobility with no land access) where users are required to pay a toll.