Emission Budget for Motor Vehicles: The total of all motor vehicle emissions identified in the State Implementation Plan (SIP) that an area can produce and still achieve the SIPs purpose which is to demonstrate attainment of the air quality standard or in some cases, demonstrate maintenance of the standards.

Emissions Sources
: Emissions are generally classified in one of three categories: stationary sources, area sources, and mobile sources.
  • Stationary sources are relatively large, fixed sources of emissions such as power plants, chemical process industries, and petroleum refineries.
  • Area sources are small, stationary and non-transportation sources that collectively contribute to air pollution (e.g., dry cleaners, bakeries, etc.)
  • Mobile sources include on-road sources such as cars, trucks, and buses, and off-road sources such as trains, ships, boats, airplanes, lawnmowers, and construction equipment.
National Ambient Air Quality Standards (NAAQS): Federal Standards that set allowable concentrations and exposure limits for various pollutants. The EPA developed the standards in response to a requirement of the Clean Air Act.

Parking Pricing: Governments may implement many pricing approaches. They may:
  • Impose or increase fees and surcharges for solo drivers or long-term parkers in public parking facilities.
  • Give price preference to car and van-poolers.
  • Tax the providers of parking, whether commercial operators of parking or all public and private entities providing parking .
  • Impose parking pricing through regional regulations, for example air quality regulations or special legislation.
  • Tie funding (especially state government) allocations for road improvements to requirements for local trip reduction plans incorporating parking pricing among other demand management strategies.
State Implementation Plan (SIP): State air quality plans required by the Clean Air Act for non-attainment and maintenance areas. The plans are prepared by state air quality agencies and include estimates of future air quality and control strategies to attain appropriate air quality standards.

Transportation Control Measures (TCM): Actions to adjust traffic patterns or reduce vehicle use to reduce air pollutant emissions. These may include HOV lanes, provision of bicycle facilities and sidewalks, ride-sharing, telecommuting, etc. Such actions may be included in a SIP if needed to demonstrate attainment of the NAAQS.

Vehicle Miles Traveled (VMT): The sum of distances traveled by all motor vehicles in a specified region.