Overview
This calculator allows users to derive NO2 from NOx wherever NOx is predicted by modelling emissions from roads. The calculator can also be used to calculate the road component of NOx from roadside NO2 diffusion tube measurements. Local authorities are advised to use the latest version of the tool for all future work that is based upon use of the 2021 reference year background maps and the EFT v12.1 onwards.
The current version of the calculator (v9.1) should only be used with the 2021 Reference Year Background Maps and the current version of the Emissions Factors Toolkit, and can be used for years 2021 to 2040. Guidance on how to use the NOx to NO2 Calculator is available in the Background Maps User Guide provided below.
Current Version
Documents
NOx to NO2 Calculator v9.1
Released: August 2024 (XLSB, 3.6MB)
Background Maps User Guide
Released: November 2024 (PDF, 743KB, 46 pages)
Details
Version 9.1 uses updated estimated regional concentrations and updated f-NO2 values from NAEI 2020 projections that are consistent with the 2021 base year LAQM background maps. It also provides the capability to include user defined f-NO2 values in both the NOx to NO2, and NO2 to NOx conversion calculations. It covers the years 2021 to 2040.
Values of f-NO2 have been developed from recent real-world roadside vehicle emissions remote sensing measurements of NO2/NOx ratios compiled by Ricardo and the University of York. Factors were developed for different vehicle types and Euro standards, with the exception of buses.The f-NO2 factors for buses were taken from the EMEP/EEA Emissions Inventory Guidebook (2019) and studies by Carslaw et al (2016) ‘Have vehicle emissions of primary NO2 peaked?’ (Faraday Discuss., 2016, 189, 439). Analysis of the Ricardo and University of York roadside vehicle remote sensing data suggests that f-NO2 factors for Euro 3, 4 and 5 diesel cars and LGVs are lower than in the EMEP/EEA Emissions Inventory Guidebook. The f-NO2 factors for Euro IV and V HGVs derived from roadside remote sensing are lower than in the EMEP/EEA Guidebook, while for Euro VI the remote sensing factors suggest higher factors than the EMEP/EEA Guidebook. The factors for individual vehicle types have been weighted according to the contribution each vehicle type makes to total NOx emissions from traffic in each of these area and road types to provide factors for overall UK traffic, urban traffic, non-urban traffic and traffic in London. The use of the updated f-NO2 factors for all vehicles except buses results in an overall significant decrease in f-NO2 factors compared to the f-NO2 factors recommended for use in version 8 of the NOx to NO2 convertor for all UK and London traffic.
The background maps and the NOx emission weightings on the f-NO2 factors are derived from NAEI emission projections, as used in the 2021 baseline projections for LAQM. Fleet turnover has been estimated using information derived from DfT and London-specific information on the vehicle fleet provided by TfL, with the central London Ultra Low Emission Zone included and the expanded ULEZ included from 2023. The NOx emission factors are based on COPERT 5.4. The baseline NOx projections include the introduction of Euro standards up to Euro 6/VI, and include the impact of the two-stage introduction for diesel cars and LGVs of the new European Real-Driving Emission (RDE) regulations. Further details on the derivation of f-NO2 factors in the NAEI are given here.
Previous Version
Documents
NOx to NO2 Calculator v8.1
Released: August 2020 (XLS, 3.2MB)
Details
Whilst local authorities are advised to use the latest version of the NOx to NO2 Calculator for all future work, in support of ongoing work, the previous version of the NOx to NO2 Calculator has been provided.
For older versions of the NOx to NO2 Calculator, or details on the basis for the f-NO2 values and background maps utilised in older versions, please contact the LAQM Helpdesk for further assistance.
