We use two 2021 census datasets to help us work this out:
The average distance travelled to work for each local area authority
The average method of transport to work for each local area authority
For each method of transport (car, bus and train) we apply carbon factors from the Department of Farming and Rural Affairs (DEFRA) and the Department for Transport (DfT).
We recognise that due to the historic nature of these datasets, there is likely to be some inconsistency in areas. And as with all data that we use, we will review and update when more becomes available.