Appendix 14.1 Glossary of Terms

Appendix 14.1 Glossary of Terms

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Table 14.1_1 Glossary



Annual Average Daily Traffic

A daily total traffic flow (24 hrs), expressed as a mean daily flow across all 365 days of the year.

Annual Average Hourly Traffic

An hourly traffic flow, expressed as a mean hourly flow across the number of hours in the year.

Air quality

Policy target generally expressed as a maximum ambient concentration to be achieved, either without exception or with a permitted number of exceedences within a specific timescale (see also air quality standard).

Air quality

The concentrations of pollutants in the atmosphere which can broadly be taken to achieve a certain level of environmental quality. The standards are based on the assessment of the effects of each pollutant on human health including the effects on sensitive sub groups (see also air quality objective).

Annual mean

The average (mean) of the concentrations measured for each pollutant for one year. Usually this is for a calendar year, but some species are reported for the period April to March, known as a pollution year. This period avoids splitting winter season between 2 years, which is useful for pollutants that have higher concentrations during the winter months.


Air Quality Management Area.

Data capture

The percentage of all the possible measurements for a given period that were validly measured.


Department for Environment, Food and Rural Affairs.


Environmental Impact Assessment.

Emission rate

The quantity of a pollutant released from a source over a given period of time.


A period of time where the concentrations of a pollutant is greater than, or equal to, the appropriate air quality standard.


Heavy Goods Vehicle.


Local Air Quality Management.


Nitrogen dioxide.


Nitrogen oxides.


Particulate matter with an aerodynamic diameter of less than 10 micrometres.

Road link

A length of road which is considered to have the same flow of traffic along it. Usually, a link is the road from one junction to the next.

µg/m3 microgrammes per
cubic metre

A measure of concentration in terms of mass per unit volume. A concentration of 1ug/m3 means that one cubic metre of air contains one microgram (millionth of a gram) of pollutant.


Updating and Screening Assessment.

Verification (modelling)

Comparison of modelled results versus any local monitoring data at relevant locations.