Report: London Ultra Low Emissions Zone Succeeded in Curbing Harmful Air Pollution

In 2019, London Mayor Sadiq Khan established the world’s first 24-hour Ultra Low Emission Zone (ULEZ) in central London to protect the city’s residents from deadly air pollution. The ULEZ imposed £12.50 fines on vehicles whose emissions exceeded certain standards. Two years later, Khan expanded the zone to include inner London within the boundaries of the North and South Circular roads.

Now, a new peer-reviewed report from the mayor’s office finds the policy has paid off months before Khan plans to expand it once again. 

“As a former lawyer, I just love looking at the evidence.The evidence today is game, set and match unequivocal,” Khan told the Evening Standard of the report. “The Ulez is the most effective policy to clean up the air in our city there has ever been.”

Among its key findings, the report revealed that

1. The number of older, highly polluting, non-compliant vehicles in the zone fell by nearly 60 percent since the ULEZ was expanded.
2. Nitrogen oxide (NOX) emissions fell by 23 percent across all of London since 2019 compared to what they would have been without the ULEZ. Within the ULEZ, NOX emissions fell by 26 percent.
3. Fine particulate matter (PM2.5) emissions fell by seven percent over the four years across all of London compared to what they would have been without the ULEZ. PM2.5 emissions fell by 19 percent within the ULEZ itself.
4. Carbon dioxide emissions fell by three percent across London since 2019 and four percent within the ULEZ.
5. NOX concentrations were 21 percent lower than they would have been without the ULEZ in inner London and 46 percent lower in central London. 
6. Nitrogen dioxide (NO2) emissions did not return to pre-pandemic levels when traffic increased, suggesting the impact of the ULEZ.
7. Average PM2.5 levels have fallen by 41 percent in inner and central London since 2017.

The ULEZ is not the only thing that has helped reduce pollution. Prior to the ULEZ, London launched a Low Emission Zone (LEZ) in 2008 applying to larger vehicles, and standards for this were updated in 2021. Vehicles are also becoming cleaner in general. 

“As time progresses and NO2 concentrations continue to decline due to Mayoral policies, local authority initiatives and the natural churn of the vehicle fleet, it is becoming increasingly complex to disentangle the impacts of each separate policy on air pollution concentrations in the different areas of London. In addition to the ULEZ and LEZ, many of the Mayor’s other policies, such as the growth of the zero emission bus and taxi fleets, will have had positive impacts on concentrations, particularly in central and inner London,” the study authors wrote.

For example, NOX emissions fell by 70 percent across Transport for London buses–the largest drop for any vehicle type–even though these were not impacted by the ULEZ. 

Khan has announced plans to expand the ULEZ to cover all London boroughs by Aug. 29, 2023. 

“As mayor, I simply won’t accept that the five million people in outer London shouldn’t be able to benefit from the same life-saving health impacts that ULEZ has already brought to the rest of our city,” Khan said, as BBC News reported. “Everyone has the right to breathe clean air.”

However, not everyone agrees with the planned expansion. Eleven outer London councils have expressed concerns that the measure will present unnecessary financial hardship to residents of areas that already enjoy better air quality than inner London. 

“Sadiq Khan’s Ulez expansion will have a negligible effect on air quality in outer London, while hitting low income and vulnerable families hardest,” City Hall Conservatives transport spokesperson Nick Rogers said, as the Evening Standard reported. “Sadiq Khan needs to listen to Londoners, scrap his expansion, and spend the money on policies that actually reduce air pollution.”

The report has answered one of the main concerns of ULEZ detractors, however.

“Many people fear that traffic will simply divert around low emission zones, worsening air pollution for those that live on the boundaries. However, data from London’s air pollution measurement network has shown that this has not happened. Instead, nitrogen dioxide alongside the North and South Circular roads has shown a strong improvement,” Imperial College London urban air pollution expert Dr. Gry Fuller, who peer-reviewed the report, said, as The Guardian reported. “Many cities in the UK and around the world are looking to follow London’s lead. I hope that the evidence here will improve the design of similar schemes more widely.”