Key findings

The findings indicate that the Mayor’s air quality policies, and in particular the ULEZ and LEZ schemes, are having an important impact on reducing the number of older, more polluting vehicles seen driving in London and on reducing the levels of harmful air pollution that Londoners are exposed to. In summary, the key findings are:

Air pollutant concentrations - general trends

Overall improvement in air quality has been observed across London. These trends are not attributable to ULEZ, however schemes and policies such as the ULEZ contribute towards accelerating these improvements.

• Average nitrogen dioxide (NO₂) concentrations in 99 per cent of all monitoring locations¹ included in the analysis have improved between 2019 and 2024, with 80 per cent of monitoring locations showing reductions of more than 10 µg/m³.

• Long term trends indicate that average NO₂ concentrations over all London zones improved at a faster rate than the rest of England average over the same time period (2017 – 2024). This is particularly notable in outer London where concentrations have improved more rapidly over recent years and are now similar to the rest of England average which has historically been lower than London².

Air pollutant concentrations - ULEZ impacts

Due to the London-wide ULEZ expansion:

• In the first year of operation, roadside NO₂ concentrations in outer London were on average up to 4.8 per cent lower than would have been expected without the London-wide ULEZ expansion.

Due to all phases of the ULEZ:

• All phases of the ULEZ have had an impact on improving air quality across the capital. In 2024, compared to a scenario without the ULEZ, harmful roadside NO₂ concentrations are estimated to be:
  • 27 per cent lower across the whole of London than they would have been without the ULEZ and its expansions.
  • 54 per cent lower in central London than they would have been without the ULEZ and its expansions.
  • 29 per cent lower in inner London than they would have been without the ULEZ and its expansions.
  • 24 per cent lower in outer London than they would have been without the ULEZ and its expansions.
• London’s more deprived communities are seeing greater benefits from the ULEZ; for some of the most deprived communities living near London’s busiest roads, there’s been an estimated 80 per cent reduction in people exposed to illegal levels of pollution³.
• Areas outside London are also seeing the impacts of the ULEZ, with roadside NO₂ concentrations within 5 km of the Greater London boundary on average 14 per cent lower in 2024 than an estimated “No ULEZ” scenario.

Air pollutant and carbon emissions

Due to the London-wide ULEZ expansion:

• Air pollutant emissions in 2024 were lower than expected compared to a scenario without the ULEZ expansion. Specifically:
  • Nitrogen oxides (NO_X) emissions from cars and vans in outer London are estimated to be 13 per cent and 16 per cent lower respectively.
  • Particulate Matter 2.5 (PM_2.5) exhaust emissions from cars and vans in outer London are estimated to be 31 per cent lower.
  • Outer London boroughs are seeing the largest impacts from the London-wide expansion. NO_X emissions are estimated to be between nine per cent and 15 per cent lower across all boroughs than would have been expected without the London-wide ULEZ expansion.

Due to all phases of the ULEZ:

• Cumulatively over a six-year period (2019 – 2024), air pollutant and carbon emissions across London are lower due to all phases of the ULEZ, compared to a scenario without the ULEZ. Specifically:
  • NO_X emissions are estimated to be 24 per cent lower.
  • PM_2.5 exhaust emissions are estimated to be 29 per cent lower.
  • CO₂ emissions are estimated to be two per cent lower.
• In 2024 alone, NO_X emissions are estimated to be between 33 per cent and 39 per cent lower across all boroughs than they would have been without the ULEZ and its expansions.

Vehicle compliance

• A larger proportion of vehicles recorded driving in London are cleaner. The London-wide compliance rate for vehicles subject to the ULEZ standards after the first year of the expansion (as of September 2024) was 96.7 per cent. For reference, compliance was 91.6 per cent in June 2023 prior to the expansion and 39 per cent in February 2017, when changes associated with the ULEZ began.

• In the expanded outer London area, ULEZ vehicle compliance is now 96.7 per cent, up from 90.9 per cent in June 2023. This is the same level of compliance as seen in inner and central London, with 96.9 per cent and 96.7 per cent respectively. Van compliance in outer London is over 90 per cent for the first time, an increase of 11.4 percentage points since June 2023.

• There are fewer older, more polluting ULEZ vehicles seen driving in the zone. There were nearly 100,000 fewer non-compliant vehicles detected in London on an average day in September 2024 compared to June 2023. This is a 58 per cent reduction in non-compliant vehicles between those dates.

Footfall and economic spend

• Despite some concerns that economic activity in outer London may be reduced as a result of the London-wide ULEZ expansion, the expansion has had no negative impact on footfall and spend in the outer London area, or at a London-wide level. The following trends were observed although the changes were not statistically significant:
  • Visitor footfall in outer London increased 1.87 per cent in the year after the London-wide ULEZ expansion, compared to an increase of 0.08 per cent across all of London.
  • Worker footfall in outer London increased by 8.89 per cent compared to 8.54 per cent across all of London.
  • Spend in outer London decreased by 3.17 per cent compared to 3.42 per cent across all of London and 3.36 per cent across the rest of England⁴.