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Access, Accessibility

The opportunity to reach a given end use within a certain time frame, or without being impeded by physical, social or economic barriers. Typically, accessibility is the extent to which transportation improvements make connections between geographic areas or portions of the region that were not previously well connected.

Air Quality

The cleanliness of the air; the fewer pollutants in the air, the better the air quality.


The route that an improvement, such as a bus or light rail line, could take through a corridor.


An alternative includes various improvements (modal options) designed to address transportation deficiencies in the project area.

Area of Potential Effect

Area of Potential Effect means the geographic area or areas within which an undertaking may directly or indirectly cause alterations in the character or use of historic properties, if any such properties exist. The area of potential effects is influenced by the scale and nature of an undertaking and may be different for different kinds of effects caused by the undertaking.


An arterial roadway serves major traffic movements or major traffic corridors. While they may provide access to abutting land, their primary function is to serve traffic moving through the area.

Average Daily Traffic (ADT)

The total volume of traffic in both directions on a highway during a time period of greater than one day but less than a year, then divided by the number of days for which traffic data was collected.


Base Year

The lead off year of data used in a study, usually the current year or a year with the most recent comprehensive data.

Build/No Build

As defined by the federal transportation legislation, Metropolitan Planning Organizations (MPOs) must demonstrate that “building” or implementing a long range plan (LRP) and Transportation Improvement Program (TIP) will provide more emissions reduction (improve air quality) than by “not building” or not implementing that same long range plan and TIP.

Bureau of Design & Environment (BDE)

The Illinois Department of Transportation, Division of Highways Bureau of Design & Environment, ensures that all department and consultant personnel preparing Phase I studies and reports and contract plans for the department are carried out by prescribed uniform criteria.



The maximum amount of traffic on any transportation facility that can be accommodated and still function.

Chicago Metropolitan Agency for Planning (CMAP)

Formed in 2005, CMAP integrates planning for land use and transportation in the seven counties (Cook, DuPage, Kane, Kendall, Lake, McHenry, and Will) of northeastern Illinois.  The new organization combined the region's two previously separate transportation and land-use planning organizations -- Chicago Area Transportation Study (CATS) and the Northeastern Illinois Planning Commission (NIPC) -- into a single agency.

Citizens Interest Group (CIG)

A group comprised of neighborhood organizations, City Council/Village Board and County Board members whose districts serve the study area Local community organizations and special interest groups.


A road that collects and distributes traffic.  Sometimes built next to an expressway to collect traffic from the area and then funnel it onto the expressway.  Generally, fewer lanes than an arterial.


The process to assess the compliance of any transportation plan, program, or project with air quality control plans. The conformity process is defined by the Clean Air Act and related amendments.

Congestion Management System (CMS)

A plan developed by a Transportation Management Area (TMA) that provides for effective management of new and existing transportation facilities using travel demand reduction and operational management strategies.


When a majority agrees upon a particular issue, while the dissenting remainder agrees that their input has been heard and duly considered and that the process as a whole was fair.

Cooperating Agencies (CA)

Per NEPA, a cooperating agency is any federal agency that has jurisdiction by law or special expertise with respect to any environmental impact involved in a proposed project.  Cooperating agencies are permitted, by request of the lead agency, to assume responsibility for developing information and preparing environmental analyses for topics about which they have special expertise.

Containerized Cargo

Cargo is commercial goods that are being transported.  Containers are standard-size, metal boxes that carry cargo and can be moved between modes, like between a ship, railcar or truck.  Container on Flatcar (COFC) and Trailer on Flatcar (TOFC) are containers or truck trailers that sit on and are transported by flatbed railcars.

Context Sensitive Solutions (CSS)

An interdisciplinary approach that seeks effective, multimodal transportation solutions by working with stakeholders to develop, build and maintain cost-effective transportation facilities which fit into and reflect the project's scenic, economic, historic, and natural surroundings.


A corridor is a general path from one point to another.

Corridor Advisory Group (CAG)

Interactive group made up of elected officials representing stakeholders that are directly affected by the project, and who have authority to enter into intergovernmental agreements.



Descriptive characteristics of populations.  Examples include age, race and ethnicity, gender, income, employment and household status.

Design Concept

In a major investment study, the type of facility (i.e. freeway, arterial, local road, etc.) being considered.

Desire Line

A straight line on a map joining the origin and destination. Desire lines are normally plotted with widths proportional to the trip volumes.


The place where a trip ends.

Draft Environmental Assessment (DEA)

A Draft Environmental Assessment (DEA) is a document submitted to the FHWA in order to comply with the NEPA process. The DEA is a study of land to determine any unique environmental attributes, considering everything from endangered species to existing hazardous waste to historical significance.



Surrounding conditions or circumstances.  Usually used as a reference to nature (the natural environment) but also can include man-made conditions (the built environment).

Environmental Assessment (EA)

A study of land to determine any unique environmental attributes, considering everything from endangered species to existing hazardous waste to historical significance.

Environmental Factors

In transportation, these factors include air, water and living (eco) systems, as well as community and social factors such as aesthetics/visual, archaeology, culture, economics, history and noise.

Environmental Justice (EJ)

Environmental Justice (EJ) at the Federal Highway Administration (FHWA) means identifying and addressing disproportionately high and adverse effects of theEnvironmental Justice (EJ) at the Federal Highway Administration (FHWA) means identifying and addressing disproportionately high and adverse effects of theagency’s programs, policies, and activities on minority populations and low-income populations to achieve an equitable distribution of benefits and burdens.

Environmental Mitigation

Methods, strategies or actions to reduce the negative effects, direct, indirect and cumulative, of transportation project on the environment.

Environmental Protection Agency (EPA)

EPA is the federal source agency of air quality control regulations affecting transportation.

Evaluation Criteria

A standard or measure that permits a comparative evaluation of an alternative.


A controlled-access, divided highway for through traffic. Cross-street access is only allowed at Expressway/Freeway interchanges.



Any death on the transportation system that occurs as a result of a moving vehicle.

Federal Highway Administration (FHWA)

Division of the U.S. Department of Transportation that funds highway planning and programs.


A controlled-access, divided highway for through traffic.  Intersections with other roads are separated by different road levels.


Commercial goods carried by a vehicle, usually a truck, plane, train or ship; cargo.


A calculation or estimate of future conditions.

Functional Classification

A method of cataloging a road’s purpose and design.  Roads are generally classified as Interstates, Freeways / Expressways, Arterials (principal or minor, urban or non-urban), Collectors (major or minor, urban or non-urban), and local roads (urban or non-urban).


Geographic Information Systems (GIS)

A computer software tool that is used to solve problems based on geographically related information. It is a system linked to a graphics system capable of collecting, storing, analyzing, manipulating and displaying spatial information.



Term used to describe higher capacity roads; also includes rights of way, bridges, railroad crossings, tunnels, drainage structures, signs, guardrails, and protective structures in connection with highways.

Historic Property

Historic property means any prehistoric or historic district, site, building, structure, or object included in, or eligible for inclusion in, the National Register of Historic Places maintained by the Secretary of the Interior. This term includes artifacts, records, and remains that are related to and located within such properties. The term includes properties of traditional religious and cultural importance to an Indian tribe or Native Hawaiian organization and that meet the National Register criteria.

Home Based Work Trip

A trip to or from home for the purpose of one’s employment.


Illinois Department of Natural Resources (IDNR)

Illinois Department of Natural Resources (IDNR) is a State Agency that manages, protects and sustains Illinois' natural and cultural resources; provides resource-compatible recreational opportunities; and promotes natural resource-related issues for the public's safety and education.

Illinois Department of Transportation (IDOT)

The Illinois Department of Transportation has responsibility for planning, construction and maintenance of Illinois' extensive transportation network.  This network encompasses highways, bridges, airports, public transit, and rail freight and rail passenger systems.


A term connoting the physical underpinnings of society at large, including, but not limited to, roads, bridges, transit, water and waste systems, public housing, sidewalks, utility installations, parks, public buildings and communications networks.


A point at which separate roadways cross, meet, or overlap.

Interstate System

The system of highways that connects the principal metropolitan areas, cities, and industrial centers of the United States. The Interstate System also connects the U.S. to internationally significant routes in Mexico and Canada. The routes of the Interstate System are selected jointly by the state department of transportation for each state and the adjoining states, subject to the approval of the U.S. Secretary of Transportation.


A multilevel highway intersection arranged so that vehicles may move from one road to another without crossing streams of traffic. (Webster)


Land Use

Refers to how land and the structures (development) on it are used, i.e., commercial, residential, retail, industrial, etc.

Level of Service (LOS)

A qualitative measure describing operational road (traffic) conditions and the perception of motorists of the existing conditions. Six levels of service are defined for each type of facility, ranging from A to F, with level of service A representing the best operating conditions and level of service F the worst. Initially used to define the road network, the concept has been expanded to include bicycle and pedestrian conditions.

Local Street

A street intended solely for access to adjacent properties.

Long Range Transportation Plan (LRTP)

In transportation planning, typically covers a twenty-year time span.  Projects expecting to use federal funding must be included in the LRTP.


Major Investment

A “high-type highway or transit improvement of substantial cost that is expected to have a significant effect on capacity, traffic, level of service or mode share at the transportation corridor or sub-area scale.”


Metra provides commuter rail service in the Chicago Metropolitan area. Metra, with 495 miles of track, serves 230 stations in the counties of Cook, DuPage, Lake, Will, McHenry and Kane.

Metropolitan Planning Organization (MPO)

Formed in cooperation with the state, the Metropolitan Planning Organization (MPO) develops transportation plans and programs for the metropolitan area. For each urbanized area, an MPO must be designated by agreement between the Governor and local units of government representing 75% of the affected population (in the metropolitan area), including the central cities or cities as defined by the Bureau of the Census, or in accordance with procedures established by applicable State or local law. The MPO for the Chicago land area is Chicago Metropolitan Agency for Planning (CMAP).

Metropolitan Statistical Area (MSA)

Census Bureau delineation for major metro areas in the U.S. Also includes standard (SMSA) and consolidated metropolitan statistical area (CMSA).


Mitigation is avoiding or minimizing impacts by reducing the degree or magnitude of the implemented action; mitigating or eliminating the impact by repairing,Mitigation is avoiding or minimizing impacts by reducing the degree or magnitude of the implemented action; mitigating or eliminating the impact by repairing,rehabilitating, or restoring the impacted environment or community resource; reducing or eliminating the impact over time by long-term preservation and maintenanceoperations; and compensating for the impact incurred.


The ability to move or be moved from place to place. Typically, mobility is the ease with which movement can occur between geographic areas or parts of the region.

Mode, Intermodal, Multimodal

Form of transportation, such as automobile, transit, bicycle and walking. Intermodal refers to the connections between modes and multimodal refers to the availability of transportation options within a system or corridor.


A mathematical formula that represents the activity and the interactions within a system so that the system may be evaluated according to various conditions: land use, population, households and employment (socio-economic), transportation, or others.


National Ambient Air Quality Standards (NAAQS)

Federal standards that set allowable concentrations and exposure limits for various pollutants.

National Environmental Policy Act (NEPA)

NEPA guides federally funded projects and projects that require a Federal permit to lessen potential damages to the environment. The NEPA process requires federal agencies to integrate environmental values into their decision-making process by considering the environmental impacts of their proposed actions and reasonable alternatives to these actions.  Environmental factors such as air quality, wildlife, vegetation, water quality, wetlands, geology, neighborhoods, park/recreation areas, utilities, visual quality, and cultural resources will be assessed. NEPA encourages early and frequent coordination with the public and resource agencies throughout the project development process.  Public comments that are received during the alternative analysis phase are considered in the draft environmental document. Following NEPA guidelines, a document called an Environmental Assessment will be prepared. The process calls for continuous environmental evaluations as alternatives are analyzed.


A graphic and/or mathematical representation of multimodal paths in a transportation system.


Operations, Operational Strategies

How a transportation network functions; operational strategies are techniques that influence how a network functions.  For example, traffic signals and signs are operational activities that control traffic.


Ozone is a colorless gas with a sweet odor. Ozone is not a direct emission from transportation sources but rather a secondary pollutant formed when hydrocarbons (HC) and nitrogen oxides (NOx) combine in the presence of sunlight. Ozone is associated with smog or haze conditions. Although ozone in the upper atmosphere protects the earth from harmful ultraviolet rays, ground level ozone produces an unhealthy environment in which to live.



Pace primarily provides bus service in suburban areas outside the City of Chicago. Within the City of Chicago, the Chicago Transit Authority provides bus service.

Park and Ride Facility

An access mode to transit in which patrons drive private automobiles or ride bicycles to a transit station, stop, or carpool/vanpool waiting area and park their vehicle in the area provided for park and ride patrons. They then ride the transit system or take a carpool or vanpool to their destinations.

Participating Agencies

Per SAFETEA-LU, a participating agency is any federal, state, tribal, regional, and local government agency that may have an interest in the project.  By definition, all cooperating agencies will also be considered participating agencies.  However, not all participating agencies will serve as cooperating agencies.

Particulate Matter (PM), (PM 10)

Any material that exists as solid or liquid in the atmosphere. Particulate matter may be in the form of fly ash, soot, dust, fog, fumes, etc. Small particulate matter, or PM 10, is less than 10 microns in size and is too small to be filtered by the nose and lungs.

Peak Hour

The 60 minute period during which the largest volume of travel is experienced.

Peak Travel Period 

The period in the morning (a.m. peak period) and afternoon or evening (p.m. peak period) when additional transportation services are needed/provided to handle higher traffic/passenger volumes. The period begins when normal travel times are increased and ends when travel times are returned to normal. In the Chicago metropolitan area, the a.m. peak period is generally 6:00 a.m. to 8:00 a.m. and the p.m. peak period is 4:00 p.m. to 6:00 p.m. each weekday.

Person Trip

A one-way trip made for any purpose, by any (usually vehicular) travel mode, by one person.

Problem Statement

A concise narrative, prepared as part of a project needs study, defining the fundamental situation or circumstance to be solved.  A problem statement will generally describe a particular situation in which an expected level of performance is not being achieved, and will list one or more important factors which cause or contribute to the unacceptable performance.

Project Study Group (PSG)

The working group for a project will consist of a Project Study Group (PSG). The PSG will make the ultimate project recommendations and decisions on this project and the membership of the PSG will evolve as the understanding of the project’s context is clarified.  Other responsibilities of the PSG include expediting the project development process, identifying and resolving project development issues, promoting partnership with stakeholders to address identified project needs and working to develop consensus among stakeholders.

Public Authority

A Federal, State, county, town, or township, Indian tribe, municipal or other local government or instrumentality with authority to finance, build, operate, or maintain toll or toll free transportation facilities.

Public Participation

The active and meaningful involvement of the public in the development of transportation plans and improvement programs. Federal transportation legislation regulations require that state departments of transportation and MPOs proactively seek the involvement of all interested parties, including those traditionally under served by the current transportation system.

Public Road

Any road or street under the jurisdiction of and maintained by a public authority and open to public traffic.

Public Transit

Generally refers to passenger service provided to the general public along established routes with fixed or variable schedules at published fares.  Related terms include transit, mass transit, public transportation or paratransit.  Transit modes include commuter rail, heavy or light transit, bus, or other vehicles designated for commercial transportation of non-related persons.

Purpose and Need

The Purpose and Need incorporates detailed technical analysis and public involvement findings to date to define the purpose of the project and the need for the improvements.


Quality of Life

A term used to describe the lifestyle conditions of an area.  Conditions include the scale and depth of opportunities or choices in housing, employment, transportation, the natural environment, education, health care, and recreational and entertainment activities.



An entire metropolitan area including designated urban and rural sub-regions.

Regional Transportation Authority (RTA)

The Regional Transportation Authority, created in 1973, oversees the operation and funding of public transit in the Chicago metropolitan area. There are three service boards under the RTA—the Chicago Transit Authority (CTA), Metra and Pace.

Regional Transportation Plan (RTP)

A Regional Transportation Plan (RTP) is a long-term blueprint of a region’s transportation system. Usually RTPs are conducted every five years and are plans for thirty years into the future. The plan identifies and analyzes transportation needs of the metropolitan region and creates a framework for project priorities.

Right-of-way (ROW)

The land (usually a strip) acquired for or devoted to transportation purposes.


Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU)

The federal transportation law enacted in 2005 that guides and funds the various programs that affect the nation’s transportation system.  The law will need to be renewed in 2010.  Previous laws were the Transportation Equity Act for the 21st Century (TEA-21) in 1998 and the Intermodal Surface Transportation Efficiency Act (ISTEA) in 1991.

Select link analysis

This analysis identifies the origins and destinations of vehicles using a specific set of links in the network.


A term used to describe social and economic factors, generally resulting from an analysis of demographics of a population.

Stakeholder Involvement Plan (SIP)

The SIP is a blueprint for defining methods and tools to educate and engage all stakeholders in the decision-making process for a project.  The SIP provides the framework for achieving consensus and communicating the decision-making process between the general public, public agencies, and governmental officials to identify transportation solutions for the project.


Technical Task Force (TTF) Group

The technical task force (TTF) groups provide a means for obtaining technical input from a diverse set of stakeholders.

Traffic Analysis Zone

In planning, a division of a study area that is represented by a centroid and used for traffic assignment purposes.

Traffic Controls

Traffic control systems are designed to reduce travel times, delays and stops, while also improving the average speed on arterial roadways and freeways. These systems include elements such as coordinated traffic signals, continuous optimization of timing plans, use of bus priority signal control systems, and implementation of computer-based traffic control and freeway traffic management. 


Generally refers to passenger service provided to the general public along established routes with fixed or variable schedules at published fares. Related terms include public transit, mass transit, public transportation or paratransit. Transit modes include commuter rail, heavy or light transit, bus, or other vehicles designated for commercial transportation of non-related persons.

Transportation (or Travel) Demand Management (TDM)

Strategies and collective efforts designed to achieve reductions in vehicular travel demand. In general, TDM does not require major capital improvements. It includes ridesharing, land use policies, employer-based measures, and pricing/subsidy policies.

Transportation Improvement Program (TIP)

This is a document prepared by states and MPOs citing projects to be funded under federal transportation programs, typically for a three to five year period. Without TIP inclusion, a project is ineligible for federal funding.

Transportation Network

Arrangement of transportation systems for the movement of passenger and cargo.  Transportation systems include grid systems, radial networks, circumferential networks and eclectic networks.

Transportation Management Area (TMA)

Defined in federal transportation legislation as all urbanized areas over 200,000 in population. Within a TMA, all transportation plans and programs must be based on a continuing and comprehensive planning process carried out by the Metropolitan Planning Organization (MPO) in cooperation with states and transit operators. The TMA boundary affects the responsibility for the selection of transportation projects that receive federal funds.

Transportation System Management (TSM)

Current TSM practices are fundamental traffic engineering actions taken to improve the operation of the highway system. TSM actions are usually categorized as "supply-side" (actions intended to increase the existing vehicle capacity on the system) and "demand-side" (actions that are designed to reduce vehicle demand on the system by increasing vehicle occupancy, see TDM). For example: 

  • Traffic engineering improvements: left- and right-turn lanes, one-way streets, bus turn out lanes.
  • Traffic control improvements: traffic signal interconnection, use of bus priority signal control.

Travel Demand Management (TDM) 

Measures designed to change single-occupant vehicle driver behavior with programs such as ridesharing (carpooling and vanpooling). Other demand-side actions include parking management strategies (like park and ride lots or preferential parking for carpooling/vanpooling) or transit service improvements (like express bus service, or by-pass ramps for buses).

Travel Demand Modeling

Travel demand modeling or travel forecasting is a major step in transportation planning. This is the process by which trip assignments are made to roadways, transit, and high-occupancy vehicles.

Travel Time

Customarily calculated as the time it takes to travel from "door-to door." In transportation planning, the measures of travel time include time spent accessing, waiting, and transferring between vehicles as well as time spent traveling.



A project, activity, or program funded in whole or in part under the direct or indirect jurisdiction of a Federal agency, including those carried out by or on behalf of a Federal agency; those carried out with Federal financial assistance; and those requiring a Federal permit, license or approval.


U.S. Army Corps of Engineers (ACOE)

U.S. Federal agency under the Department of Defense and a major Army command made up of some 37,000 civilian and military personnel, that deliver vital public engineering solutions.  The ACOE is responsible for administerating several environmental permits needed for the project.


U.S. Department of Transportation (DOT)

The principal direct federal funding and regulating agency for transportation facilities and programs. FHWA and FTA are units of the US DOT.

Urbanized Area

Area that contains a city of 50,000 or more population plus incorporated surrounding areas meeting set size or density criteria.


Vehicle Hours of Travel (VHT)

The sum of time all vehicles spend traveling, calculated most typically over a 24-hour period. This statistic is most commonly summed over some area like county, but can also be calculated for specific routes or trip purposes like work.

Vehicle Miles of Travel (VMT)

A standard area-wide measure of travel activity. The most conventional VMT calculation is to multiply the average length of trip by the total number of trips.

Volume-to-Capacity (V/C)

The number of vehicles that travel on a road divided by the theoretical capacity of the road. Actual road capacity depends on a wide variety of factors such as lane width, pavement condition, total number of lanes, weather conditions, and more.



The crossing of two or more traffic streams traveling in the same direction along a significant length of highway.



The smallest geographically designated area for analysis of transportation activity. A zone typically ranges in size from one to 10 square miles. Average zone size depends on total size of study area.