IDOT CDOT Chicago Park District


The following presents definitions for a number of terms frequently used during the development of environmental and design studies associated with the implementation of a transportation improvement.

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.

Accessible Pedestrian Signal (APS)
A traffic signal that provides auditory and/or vibrotactile information to pedestrians who are blind or have low vision.

Adaptive Signal Control (ASC)
To ease traffic congestion, adaptive signal control (ASC) technology adjusts the traffic signal timings of a network in reaction to changing traffic patterns.

Best Management Practices (BMP)
Best management practices (BMPs) are used to mitigate the effects of highways and roads on local conditions, in terms of both water quantity and water quality effects. BMPs are used to reduce peak flows, to reduce runoff volumes, and to reduce the magnitude and concentrations of constituents in runoff.

Bus-Rapid Transit (BRT)
Bus-rapid transit (BRT) systems provide more effective and efficient bus service by dedicated bus lanes, transit signal priority, and/or fewer stops on the route.

Capacity Analysis
A study done to determine the quality of operation of a given intersection or roadway segment. The quality of operation is expressed in terms of a Level of Service (LOS).

Categorical Exclusion (CE)
A category of actions which do not individually or cumulatively have a significant effect on thehuman environment.

Chicago Metropolitan Agency for Planning (CMAP)
The Chicago Metropolitan Agency for Planning (CMAP) is the comprehensive regional planning organization for the northeastern Illinois counties of Cook, DuPage, Kane, Kendall, Lake, McHenry, and Will. By state and federal law, CMAP is responsible for producing the region's official, integrated plan for land use and transportation. The agency's innovative GO TO 2040 planning campaign will develop and implement strategies to shape the region's transportation system and development patterns, while also addressing the natural environment, economic development, housing, education, human services, and other factors shaping quality of life.

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.

Complete Streets
Complete Streets are designed, operated and maintained so they are safe, comfortable and convenient for all users - pedestrians, bicyclists, transit users and motorists of all ages and abilities.

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.

Corridor Planning Committee (CPC)
A working group consisting of community leaders and other interests. The Corridor Planning Committee (CPC) helps the Project Study Group (PSG) identify community issues and helps determine community characteristics which should be taken into consideration in the planning process.

Context Sensitive Solutions (CSS)
Context sensitive solutions (CSS) is a collaborative, interdisciplinary approach that involves all stakeholders to develop a transportation facility that fits its physical setting and preserves scenic, aesthetic, historic, and environmental resources, while maintaining safety and mobility.

Vehicular Delay
The primary performance measure on interrupted flow facilities, especially at signalized intersections. For this element, average control delay is measured, which is expressed in seconds per vehicle. Control delay includes the time vehicles are slowing down approaching a traffic signal or stopped at the intersection.

Design Hourly Volume (DHV)
The two-way traffic volume for the design hour. In urban areas, the Peak Hour is used as the Design Hour.

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 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.

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

Geographic Information System (GIS)
Geographic information system (GIS) combines hardware, software, and data. GIS organizes the data in many ways that can display patterns and trends.

GO TO 2040
The Chicago Metropolitan Agency for Planning (CMAP) is leading development of GO TO 2040, the comprehensive regional plan that will guide growth in Cook, DuPage, Kane, Kendall, Lake, McHenry, and Will Counties through mid-century and beyond. In addition to land use and transportation, GO TO 2040 also addresses the full range of quality-of-life issues, including the natural environment, economic development, housing, and human services such as education, health care and other social services.

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.

Leading Pedestrian Intervals (LPI)
A leading pedestrian interval (LPI) gives pedestrians a head start into an intersection before vehicles.

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.

Moving Ahead for Progress in the 21st Century (MAP-21)
MAP-21 is a milestone for the U.S. economy and the Nation's surface transportation program. By transforming the policy and programmatic framework for investments to guide the system's growth and development, MAP-21 creates a streamlined and performance-based surface transportation program and builds on many of the highway, transit, bike, and pedestrian programs and policies established in 1991.

A permissive condition allowing individual judgment and discretion in 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.

Pertaining to or suitable for transportation involving more than one form of transportation, i.e. pedestrians, bicycles, vehicles, trucks, etc.

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 that 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.

Non-motorized transportation
(also known as Active Transportation and Human Powered Transportation) includes walking and bicycling, and variants such as small-wheeled transport (skates, skateboards, push scooters and hand carts) and wheelchair travel.

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.

Pedestrian Hybrid Beacon (PHB)
A pedestrian hybrid beacon is a device that stops traffic to allow pedestrians to cross. The beacon flashes yellow, then is steady yellow, then a steady red, then flashes red to make drivers aware to stop.

Project Study Group (PSG)
A group consisting of representatives from the Chicago Department of Transportation, the Chicago Park District, the Chicago Transit Authority, the Illinois Department of Transportation, and other State and Federal Agencies. The PSG has primary responsibility for the project development process. This group provides technical oversight and expertise in key areas including study process, agency procedures and standards, and technical approaches.

Purpose of and Need for Action
The Purpose and Need identifies and describes the proposed action and the transportation problem which it is intended to address.

Road Diet
A road diet reduces the amount of space for motor vehicles, either by eliminating through lanes or shrinking the width of lanes. The reclaimed space from a road diet is then re-allocated for other uses, such as turn lanes, bus lanes, pedestrian refuge islands, bike lanes, or more sidewalk space. Road diets often involve converting a four- or five-lane roadway into a three-lane street.

Roadway 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.

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

Rectangular Rapid Flash Beacon (RRFB)
A warning device at uncontrolled or midblock crossings, where pedestrians push a button to activate rapid flashing yellow LED lights to alert drivers to stop.

An early and open process for determining the scope of issues to be addressed in the environmental document 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 106 of the National Historic Preservation Act of 1966
Section 106 requires that a Federal agency or an agency utilizing Federal funding consider the effects a project may cause to a property which is on or eligible for the National Register of Historic Places.

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.

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 this term is used in specifying procedures, that procedure is recommended. Deviations from the specified procedure should be justified.

A stakeholder is anyone who could be affected by the project and has a stake in its outcome.

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 Tollway, CMAP ATS, 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 2040 Regional Transportation Plan (GOTO 2040), 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.

Traffic Control Device (TCD)
Traffic control devices (signals, stop and yield signs) are devices to control the speed and movement of traffic.

Transportation System Management (TSM)
Transportation system management optimizes the performance of existing infrastructure by implementing projects designed to conserve capacity and improve safety and reliability.

Transit Signal Priority (TSP)
Transit Signal Priority (TSP) makes transit service more efficient and effective by giving transit vehicles more green time and less red time at traffic signals.

Signs, maps and other graphic or audible methods to convey location and direction to travelers

Wetlands (Federal)
Those areas inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.

Wetlands (Illinois)
Land that has a predominance of hydric soils (soils which are usually wet and where there is little or no free oxygen) and that is inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances does support, a prevalence of hydrophytic vegetation (plants typically found in wet habitats) typically adapted for life in saturated soil conditions. Areas which are restored or created as the result of mitigation or planned construction projects and which function as a wetland are included within this definition even when all three wetland parameters are not present.


The evolution of transportation and environmental studies has generated a considerable number of acronyms. These have been created for the names of many Federal and State agencies, laws, studies, terms, etc. The following list identifies acronyms which may be used in conjunction with this study:




American Association of State Highway and Transportation Officials
Americans with Disabilities Act
Average Daily Traffic
Accessible Pedestrian Signal
Adaptive Signal Control
(ActiveTrans) Active Transportation Alliance
(IDOT) Bureau of Design and Environment
(IDOT District 1) Bureau of Local Roads and Streets
Best Management Practices
Bus-Rapid Transit
Chicago Area Clean Cities Coalition
Chicago Architecture Foundation
Chicago Alternative Policing Strategy
Civic Consulting Alliance
Chicago Climate Action Plan
Cook County Department of Transportation and Highways
Chicago Community Trust
Chicago Department of Transportation
Chicago Department of Public Health
Combined Design Report
Categorical Exclusion
Council on Environmental Quality
Comprehensive Environmental Response, Compensation, & Liability Information System
Code of Federal Regulations
Chicago Metropolitan Agency for Planning
Congestion Mitigation and Air Quality Improvement Program
Center for Neighborhood Technology
Congress for the New Urbanism
Corridor Planning Committee
Chicago Park District
Chicago Public Schools
Context Sensitive Solutions
Chicago Transit Authority
Draft Environmental Impact Statement
(United States) Department of Interior
Chicago Department of Innovation and Technology
Environmental Assessment
Environmental Impact Statement
Environmental Law and Policy Center
(United States) Environmental Protection Agency
(Federal) Endangered Species Act
Final Environmental Impact Statement
Federal Emergency Management Agency
Federal Highway Administration
Flood Insurance Rate Map
Freedom of Information Act
Finding of No Significant Impact
Federal Railroad Administration
Federal Transit Administration
(United States) Fish and Wildlife Service
Geographic Information System
Chicago Department of Housing and Economic Development
Illinois Commerce Commission
Illinois Department of Natural Resources
Illinois Department of Agriculture
Illinois Department of Transportation
Illinois Environmental Protection Agency
Illinois Historic Preservation Agency
Illinois Natural History Survey
Illinois Nature Preserves Commission
Illinois State Geological Survey
Illinois State Water Survey
Institute of Transportation Engineers
Land and Water Conservation Fund (Act)
Level of Service
Lincoln Park Athletic Club
Leading Pedestrian Intervals
Left Turn on Red
Leaking Underground Storage Tank
Moving Ahead for Progress in the 21st Century
Mayor's Bicycle Advisory Council
Metropolitan Planning Council
Metropolitan Planning Organization
Manual on Uniform Traffic Control Devices
Motor Vehicle Level of Service
National Ambient Air Quality Standards
National Environmental Policy Act
National Historic Preservation Act
National Highway System
North Lake Shore Drive
National Pollutant Discharge Elimination System
Natural Resources Conservation Service
National Register of Historic Places
Office of Emergency Management and Communications
Office of Underground Coordination
Office of Water Resources (IDNR)
Preliminary Environmental Site Assessment
Pedestrian Hybrid Beacon
Project Study Group
Preliminary Site Investigation
Resource Conservation and Recovery Act
Record of Decision
Rectangular Rapid Flash Beacon
Regional Transportation Authority
Right Turn on Red
Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users
State Historic Preservation Officer
Stakeholder Involvement Plan
(IDOT) Strategic Regional Arterial
Surface Transportation Program
Special Waste Assessment
Traffic Control Device
Transportation Improvement Program
Transportation System Management
Transit Signal Priority
Uniform Relocation Assistance Act
United States Army Corps of Engineers
United States Department of Agriculture
United States Department of Transportation
United States Environmental Protection Agency
United States Fish and Wildlife Service
United States Geological Survey
Underground Storage Tank