It was the end of August 2023 when London officially saw the extension of the Ultra Low Emission Zone (Ulez) come into force — the low traffic zone first introduced in 2019 to reduce car pollution, which required the most polluting vehicles to pay a daily charge of £12.50 to drive across the entire greater metropolitan area, after the measure had already been in place for more central neighbourhoods.

Since then, the ambitious plan by Mayor Sadiq Khan — aimed at clearing the British capital of smog and drastically reducing pollution-related deaths — has pressed on, weathering controversy, acts of sabotage and accusations of elitism. In 2024, one year after the introduction of Ulez, the first positive outcomes emerged, with improved air quality and a beneficial impact on children's health; today, three years on from its introduction, a new report highlights further, significant advantages.

2025: London's air quality keeps getting cleaner

Indeed. The benefits of Ulez continue to make themselves felt, and three years after its introduction, a study carried out by the Greater London Authority and covered by the British daily Guardian finds that levels of deadly pollutants — linked to a wide range of health problems, from cancer to severe lung conditions and heart attacks — have fallen, with the most significant improvements recorded in the capital's highest-risk outer areas.

The very suburban boroughs that had strongly opposed the measure pushed by Mayor Sadiq Khan are now reaping the greatest benefits, with a significant reduction in pollution achieved in part through the removal of the oldest and most polluting cars from the roads. "When I was first elected, the data showed it would take 193 years to bring London's air pollution within legal limits if we followed the logic of the time. Thanks to our policies, we could reach the targets we set ourselves as early as this year," Sadiq Khan explained. Could this be the farewell to the Dickensian London fog?

The suburbs' opposition to Ulez — and what happened next

Several outer London borough councils have over the years filed legal challenges against the introduction of the city's vast low traffic zone, so far without success. But the Ulez 6 Month Report published by the Greater London Authority leaves little room for doubt. The results, as highlighted by the Guardian, having been thoroughly reviewed by a panel of independent experts, definitively confirmed that Ulez has had a positive impact and that London's air quality has improved across the board and at a faster rate than the rest of the country.

The report in question covers the first year since the zone's expansion to the outer boroughs and is the most comprehensive analysis carried out to date. "The decision to expand Ulez was not taken lightly," London's mayor explained, "but this report shows it was the right choice for the health of all Londoners, particularly to protect children and those most vulnerable to illnesses linked to air pollution."

When major cities become laboratories of good practice (and not just of traffic and smog)

The report highlighted how air quality in the London areas covered by Ulez is improving at a faster rate than the rest of England, especially in the outer boroughs, where pollutant concentrations had been particularly worrying. In detail, climate-altering emissions showed a sharp reduction, with a decrease in atmospheric CO2 equivalent to approximately 3 million one-way flights from Heathrow to New York.

The World Health Organization is applauding too. Maria Neira, Director of Environment, Climate Change and Health at the WHO, praised the London initiative: "Improving air quality through initiatives like Ulez is crucial to protecting public health and reducing the incidence of disease. Cleaner air means healthier communities, lower rates of respiratory and cardiovascular disease, and a better quality of life."

Key figures from the report

• Levels of nitrogen dioxide (NO2), one of the leading causes of asthma and lung cancer, have fallen by 27 per cent across London.
• Emissions of fine particulate matter, better known as PM2.5 — fine enough to penetrate the lungs and secondary bronchi, and produced primarily by vehicle exhausts — have fallen by 31 per cent in outer London.
• Overall air quality has improved at 99 per cent of monitoring sites across London.

Before Ulez, pollution in London caused around 4,000 premature deaths a year

The benefits of Ulez highlighted by the report give pause for thought. In the poorer neighbourhoods of the English capital, where heavily trafficked roads sit closer to residential homes, there has been an 80 per cent reduction in the number of people exposed to high levels of pollution; before Ulez, pollution in London caused around 4,000 premature deaths a year. But the introduction of the large low traffic zone has also brought considerable benefits in terms of reducing the average age of the vehicle fleet on the roads (in Italy, one of the oldest in Europe, with an average of 12.5 years, according to Unrae). But how does Ulez work? Simply: the most polluting cars pay £12.50 per day (around €15) to drive. Petrol cars less than 19 years old and diesel cars less than 9 years old are exempt. The latest figures show that 97 per cent of vehicles currently on the road are already compliant.

Is London a model to follow? The case of Bologna

Well, considering the environmental gains — partly similar to those achieved since Bologna introduced "Città 30", with traffic-related nitrogen dioxide emissions reduced by 29 per cent — the answer would appear to be yes. In the case of the Emilian capital, those gains come on top of the benefits in terms of road safety, with a reduction in accidents and traffic, alongside an increase in sustainable mobility, with cycling, bike sharing and car sharing all growing strongly. In short, Ulez teaches us that when politicians have the courage to make unpopular but right decisions, everyone ultimately benefits. Even those who, at the start, were protesting. A message that, perhaps, we should also heed closer to home…