How TfL measures and reports compliance levels

Compliance levels in London are monitored through Automated Number Plate Recognition (ANPR) data derived from anonymised daily camera detections. To check if a vehicle meets the ULEZ standards or not, we cross-reference this data with available DVLA records, including information on vehicle type, age, Euro standards and emissions. This gives us a daily average compliance rate for each month for central, inner and outer London.

The compliance levels of vehicles on London roads over time have been published in peer-reviewed reports assessing the impacts of the ULEZ, including the most recent Inner London ULEZ Expansion 1-year report. The data shows that, based on monthly average compliance levels, 9 out of 10 cars seen driving in outer London meet the ULEZ emissions standards.

Vehicles registered to London addresses

TfL analyses registered vehicle data from the Society of Motor Manufacturers and Traders (SMMT), who compile data from the DVLA and additional information from the motor industry. The data SMMT provide accounts for vehicles registered to London addresses (residential and business) based on Euro standard, fuel type and age of vehicle.

It does not account for whether those vehicles are used or kept in London (including, for example, vehicles registered to business addresses in London). It doesn't reflect whether or how much vehicles are being driven in London, and that stationary vehicles do not incur charges. It is based on registrations per year - not what is registered in any one month.

The latest SMMT data is from 2021. It does not take into account the natural turnover of vehicles since the end of 2021, the impact of the announcement of the Mayor's decision to expand the ULEZ across all London boroughs, or the Mayor's £110m scrappage scheme, which is already taking thousands of London-registered vehicles off the roads and helping their owners make the switch to more sustainable options.

These factors are why TfL instead uses the camera network to gauge the compliance of the vehicles observed driving on London's roads. TfL is continuing to analyse compliance to prepare for the ULEZ expansion, and will be in a position to analyse 2022 SMMT data in the near future, which will provide a more up-to-date view of the vehicles registered to London addresses. However, since that data will only cover periods up to the end of 2022, it will remain less representative than the compliance rates of vehicles seen on the road from TfL's cameras which gives a more up to date view of vehicles actually being driven.

Impact on Londoners with non-compliant vehicles

The Integrated Impact Assessment (IIA) for the ULEZ expansion provided an assessment of the potential positive and negative impacts of the Proposed Scheme on the environment, equalities, health and the economy. It also identified measures to either enhance potential positive impacts or minimise negative ones. This report used the 2020 SMMT compliance data - the newest data available at that time.

The IIA noted the differences between types of compliance and looked at compliance of vehicles registered to London addresses (whether they are driven in London or not) in order to understand the impact on different groups and individuals. Section 6.3 of the IIA (page 86) refers to the existing levels of compliance of registered vehicles relative to income deprivation. This is 2020 SMMT data on vehicles registered to London addresses.

The IIA notes that in the current London ULEZ (up to but not including the north and south circular roads), registered vehicle compliance is lower (72% in 2020 SMMT data) than the observed data (92% as of May 2022).

It should be noted then that the compliance rate of vehicles registered in the zone has been lower than the compliance rates of observed vehicles in inner London, as well as in outer London.