London's Bold Bet
Since its city-wide expansion in 2023, London’s Ultra Low Emission Zone (ULEZ) has significantly cut harmful pollutants, increased vehicle compliance, and improved air quality—especially in vulnerable communities. Despite early resistance, the scheme has reshaped mobility habits with minimal economic disruption. One year on, the data offers a powerful case for bold, health-driven urban policy.
London's boldest move for cleaner air began in April 2019 with the launch of the Ultra Low Emission Zone (ULEZ) in Central London, targeting high-polluting vehicles with strict emissions charges. By 2021, it stretched into inner London—and by August 2023, it covered all London Boroughs, becoming the largest zone of its kind in the world. Designed to slash harmful emissions, boost air quality, and nudge drivers toward greener transport, ULEZ has been a game-changer.
In March 2025, Transport for London revealed the full impact report, capturing one powerful year since the city-wide rollout.
Clearing the air
Overall, the ULEZ has shown promising results in improving air quality across London. The scheme’s primary goal was to reduce harmful emissions, such as nitrogen dioxide (NO₂) and particulate matter (PM2.5), which have significant adverse effects on public health. The data collected reveal that these efforts have led to substantial improvements.
One of the most significant achievements of the ULEZ was the reduction of NO₂ levels. NO₂ is a harmful pollutant primarily produced by vehicles, especially diesel-powered ones. According to 2024 data, NO₂ roadside concentrations were 27% lower across the whole of London than they would have been without the ULEZ and its expansions. The most significant reductions were observed in central London (54%), with areas in outer London seeing a 24% reduction. These improvements are particularly important in combating respiratory diseases, such as asthma, and reducing premature deaths related to air pollution.
Roadside NO₂ levels—associated with asthma, reduced lung development, and higher risk of lung cancer—have decreased by a record 27% across the entire capital.
Particulate matter (PM2.5) has also dropped. The London-wide expansion of ULEZ led to a 31% reduction in PM2.5 emissions in outer London compared to projections without the expanded zone. This further reinforces the scheme’s success in lowering harmful air pollution levels citywide.
Notably, deprived communities—especially those near busy roads—benefited significantly from ULEZ. In these areas, it is estimated that there has been an 80% reduction in people exposed to illegal levels of pollution (defined as exceeding the UK legal limit for NO₂ of 40 µg/m3 as an annual average).
The ULEZ in London, Transport for London
The compliance revolution
Another critical aspect of ULEZ’s success is the compliance rate of vehicles. The ULEZ aims to encourage drivers to change their behaviour—by upgrading to cleaner vehicles or shifting to alternative modes. Non-compliant vehicles must pay a daily charge for driving within the zone, unless subject to a discount or exemption. By September 2024, 96.7% of vehicles subject to the ULEZ were compliant with its emissions standards, an increase from 91.6% in June 2023.
This marks a substantial improvement in the number of vehicles meeting the Euro 4 standard for petrol vehicles and Euro 6 for diesel vehicles. The same compliance rate—96.7%—was recorded in outer London, up from 90.9% just a few months earlier.
The number of non-compliant vehicles detected daily fell by 58% between June 2023 and September 2024. This suggests that a significant number of drivers have either upgraded their vehicles or stopped driving in the zone altogether.
This increased compliance has been accompanied by a noticeable shift toward electric and hybrid vehicles. Alternative-fuel vehicle registrations have continued to rise across the UK, and it is likely that many drivers have opted for these models specifically to avoid ULEZ charges. Their adoption plays a vital role in reducing the city’s overall emissions.
Clean air, cleaner impact
While the primary goal of ULEZ is to improve air quality, there were concerns that the expanded zone might negatively affect businesses and economic activity—particularly in outer London.
However, the data collected in the first year suggest these concerns were largely unfounded.
Visitor footfall in outer London increased by 1.87% in the year following the expansion, compared to a modest 0.08% increase across all of London. Worker footfall in outer London rose by 8.89%, slightly higher than the 8.54% increase seen citywide. This indicates that businesses in outer London were not significantly harmed by the ULEZ expansion.
In-store consumer spending in outer London did see a slight decrease of 3.17%, but this was slightly less than the overall decrease of 3.42% across London and 3.36% in the rest of England. Despite some initial concerns, the ULEZ did not cause significant financial harm to the region’s economy.
Map showing the Ultra Low Emission Zone from 29 August 2023, Transport for London
How Londoners are adapting to ULEZ
Public perception of the ULEZ has been mixed. While the policy has gained support for its clear health and environmental benefits, some opposition has come from residents in outer London who feel the financial burden of upgrading vehicles.
Protests and campaigns against the expansion have highlighted this burden, particularly for small businesses and lower-income residents. Some argue that the cost of upgrading to compliant vehicles is too high and that the daily charge is unfair. In response, the Mayor of London launched a £210 million scrappage scheme to help eligible Londoners switch to cleaner transport.
Despite the opposition, the rising compliance rates suggest that many Londoners have accepted the scheme and made necessary adjustments. The ULEZ, as part of the Mayor’s broader Transport Strategy, has also led to noticeable changes in travel behaviour. With growing awareness of air pollution, more residents have opted for public transport, cycling, or walking—especially in areas previously affected by high emissions.
From vision to reality
In conclusion, the ULEZ has yielded positive results in improving air quality and promoting cleaner transport options. Despite initial concerns about its economic impact, the scheme has proven effective in reducing pollution without major disruption to economic activity.
Ultimately, the success of the ULEZ will be judged by whether it delivers long-term health improvements—especially for vulnerable groups and those living in areas once plagued by pollution. But after one full year of citywide operation, it is already clear that London’s bold approach to air quality is working.
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About the author:
Melina Zarouka, Access Cluster Lead & Urban Nodes Taskforce Co-coordinator, POLIS. Zarouka leads the Access Cluster and coordinates the Urban Nodes Taskforce at POLIS, where she oversees access and parking projects. With a background in sustainable transport and smart mobility consulting, she holds degrees in Transport and Civil Engineering.
ULEZ London, Lorna Roberts