Nature and Biodiversity

London’s low emissions zone has reduced pollution levels by more than a quarter, new study finds

Emissions of PM2.5 particulates within the ULEZ are estimated to have dropped by 19%, or 80 tonnes.

Emissions of PM2.5 particulates within the ULEZ are estimated to have dropped by 19%, or 80 tonnes. Image: Unsplash/Mougrapher

Stefan Ellerbeck
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This article is part of: Centre for Nature and Climate

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  • London’s Ultra Low Emission Zone (ULEZ) was launched in 2019 to reduce pollution from road vehicles.
  • New research has found that air pollution has been significantly reduced both inside and outside the zone as a result.
  • The ULEZ is set to be expanded in August 2023 with the aim of reducing air pollution for five million more Londoners.

More than nine million people live in London. Like most other big capital cities, air pollution is a big problem.

Traffic on London’s busy roads produces almost 50% of its air pollution. An estimated 4,000 London residents died prematurely in 2019 through illnesses linked to long-term exposure to dirty air. More than half a million Londoners will develop diseases linked to air quality over the next three decades if no further action is taken, according to the Greater London Authority (GLA).

Some of the most dangerous air pollutants are nitrogen oxides (NOx), which can damage the human heart and lungs, and fine particulate matter (PM2.5) which can penetrate the lungs and bloodstream increasing the risks of cancer, strokes, heart and lung disease.

London’s drive for cleaner air

London first moved to tackle traffic flow and emissions issues in 2003 with the creation of the Congestion charge in the city centre. In 2008 the Low Emission Zone (LEZ) was set up to target air quality issues focusing on larger commercial vehicles.

In 2019, the Ultra Low Emission Zone (ULEZ) was created with stricter emission standards also applying to cars and motorcycles, and was expanded to cover a larger area of the city in 2021. Drivers of more polluting vehicles inside the zone must pay a daily charge of $15.

Late last year, the city’s mayor Sadiq Khan confirmed that the latest expansion of the ULEZ will come into effect in August 2023. This will expand the current scheme to London’s suburbs and an estimated five million more of its citizens.

The ULEZ will more than double in size from 29 August, 2023.
The ULEZ will more than double in size from 29 August, 2023. Image: GLA

London’s improved air quality

A new study commissioned by the GLA has found that the existing ULEZ scheme which was introduced in 2019, and expanded in 2021, has made a significant impact on reducing pollution in London.

The research found that emissions of nitrogen oxides within the ULEZ fell by 5,000 tonnes, or 26% since 2019. Across the whole of London, they dropped by 23% (13,500 tonnes).

Emissions of PM2.5 particulates within the ULEZ are estimated to have dropped by 19%, or 80 tonnes. PM2.5 levels dropped by 180 tonnes or 7% across the whole of London during the same period.

The research found that emissions of nitrogen oxides within the ULEZ fell by 5,000 tonnes, or 26% since 2019.
The research found that emissions of nitrogen oxides within the ULEZ fell by 5,000 tonnes, or 26% since 2019. Image: GLA

The evidence from the report also suggests that the ULEZ doesn’t seem to have pushed road traffic to drive around the edge of it to avoid paying the charge.

The GLA says: “All air quality monitoring sites on the boundary roads recorded large reductions in NO2 (nitrogen dioxide) concentrations and there has been an estimated reduction of 19-27% compared to a scenario without the ULEZ with the impact increasing over time. Showing … there has been no displacement of pollution to the boundary.”


The ULEZ has resulted in fewer and cleaner vehicles

The report also says there has been an overall reduction in traffic flows and vehicles in the zone. In October 2022, there were 47,000 fewer vehicles in the zone on an average day which is a reduction of 5%.

A large majority (94.4%) of vehicles driving in the zone on an average day met the ULEZ standards a year following the expansion. This is a 39% increase from when the expansion was announced in 2017.

The study found that vehicles using London’s roads are also getting cleaner. There has been an almost 60% reduction in more polluting vehicles, which is 74,000 fewer per day on average.

This is, in part, due to a shift to electric vehicles among private-hire and ride-share companies, such as Uber, which cover many more miles per day than privately owned vehicles.

"In London, Uber drivers are going electric eight times faster than the general population," says Chris Hook, head of Sustainability Strategy at Uber. "Progressive policies from City Hall, such as ULEZ and Congestion Charge exemptions for electric vehicles, have played a significant role in helping London to become the global leader in Uber’s electrification efforts, where we are aiming to become an all-electric platform in 2025."

The ULEZ has also reduced London’s carbon footprint. The GLA says, “Cumulatively since 2019, it is estimated the ULEZ has led to a reduction of around 800,000 tonnes of CO2 emissions from vehicles across London over the four-year period compared to without the ULEZ, a saving of 3%. Within the ULEZ area this is a saving of 290,000 tonnes, a reduction of 4% over the same period.”


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Opposition to ULEZ expansion

Some local councils and politicians have criticized London mayor Sadiq Khan’s plan to expand the ULEZ further, the Guardian reports.

Critics say that people living in London’s outer suburbs rely on cars more than residents of inner London. They say it is therefore unfair to expect people with older, non-compliant vehicles to either pay the ULEZ charge on a regular basis, or have to buy more modern ULEZ-compliant vehicles.

However, in a video tweeted by Mayor Khan, he says the latest expansion of the ULEZ must go ahead in order to provide cleaner air and protect public health.

The GLA says four out of five vehicles that use outer London’s roads already meet ULEZ standards, and that a $132 million scrappage scheme will help “support disabled and low-income Londoners, charities and sole traders to help replace the most polluting vehicles”. It also says all proceeds from ULEZ charges are invested back into the city’s public transport infrastructure.

Accelerating the global transportation transition

Greenhouse gas emissions from the mobility sector are predicted to double by 2050. Road vehicles contribute around two-thirds of mobility emissions and cause more than half of air pollution in cities.

The Global New Mobility Coalition is a platform initiated by the World Economic Forum with support from the ClimateWorks Foundation. It aims to support the transition to cleaner, safer and more inclusive transportation systems.

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