Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration

Office of Planning, Environment, & Realty (HEP)
Planning · Environment · Real Estate

HEP Events Guidance Publications Glossary Awards Contacts

Planning Glossary

Glossary Listing

View All | # | | A | B | C | D | E | F | G | H | I | J | K | L | M | N O | P | Q | R | S | T | U | V | W | X | Y | Z

Keyword Definition
Average Annual Daily Traffic (AADT) The total volume of traffic on a highway segment for one year, divided by the number of days in the year.
Average Annual Daily Truck Traffic (AADTT) The total volume of truck traffic on a highway segment for one year, divided by the number of days in the year.
Area Source Small stationary and non-transportation pollution sources that are too small and/or numerous to be included as point sources but may collectively contribute significantly to air pollution (e.g., dry cleaners).
Arterial Street A class of street serving major traffic movements (high-speed, high volume) for travel between major points.
Attainment Area An area considered to have air quality that meets or exceeds the U.S. Environmental Protection Agency (EPA) health standards used in the Clean Air Act. Nonattainment areas are areas considered not to have met these standards for designated pollutants. An area may be an attainment area for one pollutant and a nonattainment area for others.
Allocation An administrative distribution of funds for programs that do not have statutory distribution formulas.
Apportionment 1) A term that refers to a statutorily prescribed division or assignment of funds. An apportionment is based on prescribed formulas in the law and consists of dividing authorized obligation authority for a specific program among the States. 2) The distribution of funds as prescribed by a statutory formula.
Appropriations Act Action of a legislative body that makes funds available for expenditure with specific limitations as to amount, purpose, and duration. In most cases, it permits money previously authorized to be obligated and payments made, but for the highway program operating under contract authority, the appropriations act specifies amounts of funds that Congress will make available for the fiscal year to liquidate obligations.
Authorization Act Basic substantive legislation that establishes or continues Federal programs or agencies and establishes an upper limit on the amount of funds for the program(s). The current authorization act for surface transportation programs is the Transportation Equity Act for the 21st Century (TEA-21).
Accident (Aircraft) As defined by the National Transportation Safety Board, an occurrence incidental to flight in which, as a result of the operation of an aircraft, any person (occupant or nonoccupant) receives fatal or serious injury or any aircraft receives substantial damage.
Air Carrier The commercial system of air transportation comprising large certificated air carriers, small certificated air carriers, commuter air carriers, on-demand air taxis, supplemental air carriers, and air travel clubs.
Airport A landing area regularly used by aircraft for receiving or discharging passengers or cargo.
Alternative Fuels The Energy Policy Act of 1992 defines alternative fuels as methanol, denatured ethanol, and other alcohol; mixtures containing 85 percent or more (but not less than 70 percent as determined by the Secretary of Energy by rule to provide for requirements relating to cold start, safety, or vehicle functions) by volume of methanol, denatured ethanol, and other alcohols with gasoline or other fuels. Includes compressed natural gas, liquid petroleum gas, hydrogen, coal-derived liquid fuels, fuels other than alcohols derived from biological materials, electricity, or any other fuel the Secretary of Energy determines by rule is substantially not petroleum and would yield substantial energy security and environmental benefits.
Amtrak Operated by the National Railroad Passenger Corporation, this rail system was created by the Rail Passenger Service Act of 1970 (Public Law 91-518, 84 Stat. 1327) and given the responsibility for the operation of intercity, as distinct from suburban, passenger trains between points designated by the Secretary of Transportation.
Arterial Highway A major highway used primarily for through traffic.
Asphalt A dark brown to black cement-like material containing bitumen as the predominant constituent. The definition includes crude asphalt and finished products such as cements, fluxes, the asphalt content of emulsions, and petroleum distillates blended with asphalt to make cutback asphalt. Asphalt is obtained by petroleum processing.
Average Haul The average distance, in miles, one ton is carried. It is computed by dividing ton-miles by tons of freight originated.
Average Passenger Trip Length (Bus/Rail) Calculated by dividing revenue passenger-miles by the number of revenue passengers.
American Institute of Certified Planners (AICP) The American Planning Association's professional institute that provides recognized leadership nationwide in the certification of professional planners, ethics, professional development, planning education, and the standards of planning practice.
Accident An incident involving a moving vehicle. Includes collisions with a vehicle, object, or person (except suicides) and derailment/left roadway. (FTA2) Occurrence in a sequence of events that produces unintended injury, death or property damage. Accident refers to the event, not the result of the event. (NSC1)
Airplane An engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings. (14CFR1)
Airship An engine-driven lighter-than-air aircraft that can be steered. (14CFR1)
Alcohol Concentration (AC) The concentration of alcohol in a person's blood or breath. When expressed as a percentage it means grams of alcohol per 100 milliliters of blood or grams of alcohol per 210 liters of breath. (49CFR383)
Altitude The vertical distance of a level, a point or an object considered as a point measured in feet Above Ground Level (AGL) or from Mean Sea Level (MSL). 1) MSL Altitude. Altitude expressed in feet measured from mean sea level. 2) AGL Altitude. Altitude expressed in feet measured above ground level. 3) Indicated Altitude. The altitude as shown by an altimeter. On a pressure or barometric altimeter it is altitude as shown uncorrected for instrument error and uncompensated for variation from standard atmospheric conditions. (FAA4)
Americans With Disabilities Act (ADA) The legislation defining the responsibilities of and requirements for transportation providers to make transportation accessible to individuals with disabilities. (FTA1)
Automobile A privately owned and/or operated licensed motorized vehicle including cars, jeeps and station wagons. Leased and rented cars are included if they are privately operated and not used for picking up passengers in return for fare. (FHWA3)
American Association of State Highway & Transportation Officials (AASHTO) A nonprofit, nonpartisan association representing highway and transportation departments in the 50 states, the District of Columbia and Puerto Rico. It represents all five transportation modes: air, highways, public transportation, rail and water. Its primary goal is to foster the development, operation and maintenance of an integrated national transportation system.
Association of Metropolitan Planning Organizations (AMPO) AMPO is a nonprofit, membership organization established in 1994 to serve the needs and interests of "metropolitan planning organizations (MPOs)" nationwide. AMPO offers its member MPOs technical assistance and training, conferences and workshops, frequent print and electronic communications, research, a forum for transportation policy development and coalition building, and a variety of other services.
American Planning Association (APA) A nonprofit public interest and research organization committed to urban, suburban, regional, and rural planning. APA and its professional institute, the American Institute of Certified Planners, advance the art and science of planning to meet the needs of people and society.
American Public Transportation Association (APTA) Acting as a leading force in advancing public transportation, APTA serves and leads its diverse membership through advocacy, innovation, and information sharing to strengthen and expand public transportation.
Auto inspection and maintenance (IM) Programs require the testing of motor vehicles in parts of the country with unhealthy air and the repair of those that do not meet standards.
Arterial A class of roads serving major traffic movements (high-speed, high volume) for travel between major points.
Annual Funding Agreement A negotiated annual written funding agreement between a Self-Governance Indian Tribal Government (ITG) and the Secretary of the Interior, authorizing the ITG to plan, conduct, consolidate, and administer programs, services, functions, and activities or portions thereof previously administered by the Department of the Interior through the BIA, and other programs for which appropriations are made available for the ITG through the Secretary of the Interior from agencies other than Department of the Interior (DOI).
Appropriation Authorization of funding expenditures from Congress.
Areawide Control Schedule An accounting and project management tool that is developed from tribal Transportation Improvement Programs, tribal control schedules, and tribal priority lists to identify detailed project information for the expenditure of IRR funds for the current and next four fiscal years.
Audit Periodic investigation of financial statements and their relationships to planned or permitted expenditures.
Authorization Basic substantive legislation or that which empowers an agency to implement a particular program and also establishes an upper limit on the amount of funds that can be appropriated for that program
Analysis of Alternatives Understanding how the transportation system and its components work such as information on the costs, benefits and impacts of potential chances to the system.
Air Quality Conformity The link between air quality planning and transportation planning

View All | # | | A | B | C | D | E | F | G | H | I | J | K | L | M | N O | P | Q | R | S | T | U | V | W | X | Y | Z

Top of Page
Updated: 03/21/2012
HEP Home Planning Environment Real Estate
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000