For developments where an overall significant impact to local air quality is determined a damage cost calculation should be undertaken to determine an appropriate sum to be spent on mitigating the impact on air quality. In order to complete a damage cost calculation, the following information is required:
Trips generated by the development as annual average daily trips (AADT);
Average distance travelled (can be obtained from the National Travel Survey) or assume average trip of 10km;
The EfT spreadsheet provided by Defra should be used to establish the total emissions in tonnes per year.
The damage cost in £/tonne can be obtained from the Defra guidance – Air Quality Damage Cost Guidance (July 2019).

A five-year damage cost should be determined for the scheme as follows:
EFT output for each pollutant x damage cost x 5 years
Details of the measures to be provided with this sum should be agreed in consultation with the relevant EHO.