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Transportation Air Quality Selected Facts and Figures

Terms

AFV

Alternative-fuel vehicle.

AVCV

Automated vehicle/connected vehicle.

CAA

The Clean Air Act.

CAAA

The Clean Air Act Amendments of 1990.

CMAQ

Congestion Mitigation and Air Quality Improvement Program.

CNG

Compressed natural gas.

CO

Carbon monoxide, a product of incomplete combustion.

CO2

Carbon dioxide, not a criteria pollutant but a greenhouse gas.

Condensables

PM2.5 formed in the atmosphere from precursor gases, such as sulfur dioxide and oxides of nitrogen.

EPA

U.S. Environmental Protection Agency.

GHG

Greenhouse gas.

HC

Hydrocarbons, gaseous compounds made of carbon and hydrogen; the term is used interchangeably with VOCs.

I/M

Inspection and maintenance.

LNG

Liquefied natural gas.

LPG

Liquefied petroleum gas.

Maintenance area

Any geographic region previously designated as a nonattainment area and subsequently redesignated attainment subject to a maintenance plan.

MOVES

Motor Vehicle Emission Simulator.

MSAT

Mobile source air toxics.

NAAQS

National Ambient Air Quality Standards, federally established standards for pollutant concentrations that states, cities, and towns must meet by specified deadlines.

NEI

National Emissions Inventory.

Nonattainment area

A designated geographic area that has failed to meet the National Ambient Air Quality Standards.

Non-road engines

Aircraft, trains, boats, off-road recreational vehicles, farm and construction equipment, and yard tools.

NOx

Oxides of nitrogen, a collective term for all compounds of nitrogen and oxygen, including nitrogen monoxide and nitrogen dioxide.

NO2

Nitrogen Dioxide.

O3

Ozone, an oxygen compound that can develop when oxides of nitrogen, volatile organic compounds, and sunlight interact in the lower atmosphere; the primary constituent of smog.

On-road vehicles Cars, vans, buses, light-duty and heavy-duty trucks, and motorcycles.

PM

Particulate matter.

PM10

Particulate matter with a diameter less than 10 micrometers.

PM2.5

Particulate matter with a diameter less than 2.5 micrometers.

Point and area sources

Stationary sources of emissions, including electric utilities, factories, petroleum refineries, dry cleaners, and others.

ppm

Parts per million.

Precursors

Pollutants that contribute to the formation of other pollutants; hydrocarbons and oxides of nitrogen are precursors of ozone and particulate matter.

SIP

State Implementation Plan.

SO2

Sulfur dioxide.

TCM

Transportation control measure.

ULSD

Ultra low-sulfur diesel.

VMT

Vehicle miles traveled.

VOCs

Volatile organic compounds, gaseous compounds made of carbon and hydrogen; the term is used interchangeably with HC.

Updated: 5/3/2016
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