• Home
  • >
  • Emissions Factors Toolkit

Emissions Factors Toolkit


The Emissions Factors Toolkit (EFT) is published by Defra and the Devolved Administrations to assist local authorities in carrying out Review and Assessment of local air quality as part of their duties under the Environmental Act 1995.

The EFT allows users to calculate road vehicle pollutant emission rates for NOx, PM10, PM2.5 and CO2 for a specified year, road type, vehicle speed and vehicle fleet composition.

The EFT is updated periodically due to updates to underlying data including vehicle fleet composition and emissions factors. Users are therefore advised to check this page regularly to ensure they are using the most up to date version of the tool for their studies.

Current Version


EFT v10.1

Released: August 2020 (XLSB, 5.9MB)

EFT v10.1 User Guide 

Released: August 2020 (PDF, 0.8MB, 41 pages)


The current version of the EFT is version 10.1.

The accompanying EFT User Guide explains in detail the methodology, datasets and assumptions used in the development of the EFT. It consolidates previously available information and guidance on the use of the EFT, and provides information regarding previous versions (changes and updates).

A summary of the key updates are detailed below:

  • Use of the latest COPERT 5.3 NOx and PM emissions factors, updated from COPERT 5.0.
  • Outside of London, the default fleet split assumptions, vehicle size distributions and Euro class compositions have been updated. These are based on a set of traffic activity projections from the Department for Transport (DfT) (RTF 2018, rebased to 2017 NAEI) and DfT car sale projections (April 2019) including the uptake of low carbon passenger cars and LGVs with electric and hybrid electric propulsion systems.
  • Within London, the default fleet split assumptions and euro class compositions are still based on bespoke vehicle fleet information and projections for London provided by TfL in early 2018. These datasets are inclusive of the impact from 2019 onwards of the Ultra-Low Emissions Zone (ULEZ) in central London, the TfL bus fleet meeting the ULEZ requirements London-wide in 2020 and all new taxis registered from 2018 onwards being Zero Emissions Capable (ZEC). They do not include the impact of the full ULEZ expansion to the North and South Circular Roads in 2021, nor the tightening of the Low Emission Zone (LEZ) standards for heavier vehicles in 2021.
  • Updated and simplified Advanced Option ‘Fleet Projection Tool’.
  • Updated f-NO2 values based on the latest available ‘Primary NO2 Emission factors for road transport (2020 version)’ from the National Air Emissions Inventory.
  • Minor bug fix relating to calculation of primary fraction of NO2 from buses.


Please Note: The default fleet projections in EFT v10.1 are based on fleet growth assumptions which were current before the Covid-19 outbreak in the UK. In consequence, default fleet outputs from the tool do not reflect short or longer term impacts on emissions in 2020 and beyond resulting from behavioural change during the national or local lockdowns.

Previous Version


EFT v9.0

Released: May 2019 (XLSB, 6.1MB)

EFT v9.0 User Guide

Released: May 2019 (PDF, 1.1MB, 36 pages)


Whilst local authorities are advised to use the latest version of the EFT for all future work, in support of ongoing work, the previous version of the EFT has been provided.

For older versions of the EFT please contact the LAQM Helpdesk for further assistance.

LAQM Helpdesk
Skip to content