A citywide charging zone pushed drivers toward cleaner vehicles, accelerating air-quality gains without reducing outer London footfall or spend.
The big idea
CASE STUDY PRESENTATION
London's ULEZ Expansion Cuts Air Pollution
London expanded its Ultra Low Emission Zone citywide, cutting roadside NO₂, emissions and non-compliant vehicles in its first year.
Case Study
MitigationTransportationRegulation & governancePhysical/technical solutionsEquity & inclusionairquality
- 27% lower roadside NO₂
- 96.7% vehicle compliance
- No negative footfall impact
So what?
1
The Challenge
London faced persistent health risks from air pollution, even as scientific evidence and WHO guidance stressed that no safe level exists. Before the citywide expansion, outer London had many people and roads outside the tighter ULEZ boundary. The challenge was to cut emissions from older vehicles across the whole capital while tracking equity and economic impacts.
2
The Plan
The plan was to scale the ULEZ from a smaller clean-air zone to a London-wide policy covering nine million people. The evaluation combined observed monitoring data with modelling against no-ULEZ scenarios. It also assessed compliance and economic indicators to test both environmental and local business concerns.
Step 1
The Mayor expanded the ULEZ boundary to cover all London boroughs, matching the Low Emission Zone boundary for heavy vehicles.
Step 2
Vehicles driving in the zone were assessed against ULEZ emissions standards, increasing incentives to use cleaner vehicles.
Step 3
TfL and GLA analysed monitoring sites, traffic, vehicle compliance, emissions, exposure and economic indicators.
Step 4
Results were compared with estimated scenarios without the ULEZ and its expansions to isolate policy effects.
Step 5
An independent international advisory group reviewed and quality-assured the analysis method.
3
The Results
27%
Roadside NO₂ across London was estimated lower than without the ULEZ and its expansions.
96.7%
Vehicles subject to ULEZ standards were compliant across London by September 2024.
58%
Non-compliant vehicles detected on an average day fell between June 2023 and September 2024.
24%
NOx emissions across London were estimated lower cumulatively from 2019 to 2024.
The first year of the London-wide expansion showed cleaner vehicles, lower emissions and reduced roadside pollution compared with no-ULEZ scenarios. Outer London saw direct benefits from the expansion, while all ULEZ phases together delivered larger citywide reductions. The report found that outer London footfall and spend were not negatively affected.
4
Key Lessons
The London-wide ULEZ shows that a clear emissions standard can shift the vehicle fleet quickly when applied at metropolitan scale. Independent review and comparison with a no-policy scenario helped separate policy impacts from wider air-quality trends. Monitoring economic indicators also addressed concerns about effects on outer London high streets.
- Limited zone coverage
- Older vehicles on roads
- Unequal pollution exposure
Before
- London-wide ULEZ
- Cleaner fleet compliance
- Deprived areas benefited
After
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