Under a GHG emissions trading scheme, permits to emit can initially either be given away for free, usually under a ‘grandfathering’ approach based on past emissions in a base year or an ‘updating’ approach based on the more recent emissions. The alternative is to auction permits in an initial market offering.

The release of substances (e.g. CO, NOx, PM, greenhouse gases incl. CO2, VOCs) into the atmosphere. (see Vehicle Emissions)

Refers to the air quality in a particular region or area. Most countries set vehicle emission and fuel quality requirements to meet ambient air quality targets. In the 1990’s the US established the Clean Air Act, which set Ambient Air Quality Targets covering the entire country, although the states do much of the work to carry out the Act. EPA calls these pollutants criteria air pollutants because the agency has regulated them by first developing health-based criteria (science-based guidelines) as the basis for setting permissible levels. One set of limits (primary standard) protects health; another set of limits (secondary standard) is intended to prevent environmental and property damage. A geographic area that meets or does better than the primary standard is called an attainment area; areas that don't meet the primary standard are called nonattainment areas.

In 1996 the European Union established a Framework Directive 96/62/EC on ambient air quality assessment and management. This Directive covers the revision of previously existing legislation and the introduction of new air quality standards for previously unregulated air pollutants, setting the timetable for the development of daughter directives on a range of pollutants. The list of atmospheric pollutants covered includes sulphur dioxide, nitrogen dioxide, particulate matter, lead and ozone – pollutants governed by already existing ambient air quality objectives- and benzene, carbon monoxide, poly-aromatic hydrocarbons, cadmium, arsenic, nickel and mercury.

Is equivalent to 42 gallons (oil)

Targets for reducing emissions are often defined in relation to a base year. With regard to Green House Gas (GHG) emissions, in the Kyoto Protocol, 1990 is the base year for most countries for the major GHGs; 1995 can be used as the base year for some of the minor GHGs.

Conventional gasoline blendstock intended for blending with oxygenates downstream of the refinery where it was produced. CBOB must become conventional gasoline after blending with oxygenates. Motor gasoline blending components that require blending other than with oxygenates to become finished conventional gasoline are reported as "All Other Motor Gasoline Blending Components." Excludes reformulated blendstock for oxygenate blending (RBOB).

The release of substances (e.g. CO, NO_X, PM, greenhouse gases incl. CO₂, VOCs) into the atmosphere. (see Vehicle Emissions)

In the context of transportation, fuel efficiency refers to the energy efficiency of a particular vehicle. It is given as a ratio of distance units per a unit amount of input fuel. Fuel efficiency can be reported in terms of fuel consumption or fuel economy. While fuel economy and fuel consumption are related, the relationship is not linear. If the goal is to gain direct GHG insights, it can be gained through fuel consumption. This is because CO₂ emissions are directly and linearly related to fuel consumption. Also see fuel economy, fuel consumption.
 

Distance travelled per fuel consumed such as "miles per gallon" (mpg) (prevalent in the U.S.) or "kilometers per liter"(km/l) (prevalent in Asian countries such as India and Japan). If the penalty and taxation structure of a fuel efficiency program is intended to reflect GHG performance, all calculations must be performed based on fuel consumption and then converted to their fuel economy equivalent values. Also see fuel efficiency, fuel consumption.
 

Fuel consumed per distance traveled such as "liters per 100 kilometers" (L/100-km) (common in Europe, Canada and Australia). If the penalty and taxation structure of a fuel efficiency program is intended to reflect GHG performance, it must be based on fuel consumption. Also see fuel efficiency, fuel economy.