Defra updates Emissions Factors Toolkit

A tool which can be used by local authorities to assess potential emission levels from road transport has been updated by the Department for Environment, Food and Rural Affairs (Defra).

Version 8.0 of the Emissions Factors Toolkit (EFT), a Microsoft Excel-based calculation tool, was published this week by Defra and the devolved administrations, having last been updated in June 2016.

The tool can be used to calculate emissions on motorways, urban and rural roads based on factors including road type, vehicle speed and vehicle fleet composition

The updated toolkit can be accessed via Defra’s Local Air Quality Management (LAQM) website.

The toolkit can be used to assist local authorities in carrying out assessments of local air quality as part of their duties under the Environment Act 1995.

According to Defra, the tool can be used to understand the potential value of policy interventions on road traffic emissions such as Clean Air Zones (CAZs) or other measures that might form part of the UK national plan on compliance with EU Limit Values.


The tool allows users to calculate road vehicle pollutant emission rates for oxides of nitrogen (NOx) and Particulate Matter (PM10 and PM2.5), for a specified year, road type, vehicle speed and vehicle fleet composition.

Carbon dioxide (CO2) emission rates can also be calculated for petrol, diesel and alternative fuelled vehicles.

The layout of the updated EFT is similar to previous versions of the tool

The latest version includes emissions rates for 2015 through to 2030, taking into account fleet composition data for motorways, urban and rural roads, scaling factors reflecting improvements in the quality and technology conversions in the national fleet.

Guidance documents published by Defra indicate that the latest version incorporates updated NOx and PM speed emission coefficient equations.

An accompanying EFT User Guide has been published alongside the latest version of the tool, which explains in detail the methodology, datasets and assumptions used in the development of the EFT.

Local authorities are advised to use the latest version of the EFT for all future work.

Related Links
LAQM – Emissions Factors Toolkit


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