Harrow Council was one of four London boroughs that launched a failed attempt to stop the expansion of the capital’s low emission zone with a judicial review.
But a new City Hall study has found that there was an estimated reduction of 15.2% in Nitrogen Oxide (NOx) emissions last year in Harrow compared to a scenario in which the policy was not implemented.
This was among the largest reductions of any London borough.
Other boroughs that saw decreases of 15% or more include Enfield, Sutton, Merton, Bromley, Croydon and Havering.
Elsewhere in north London, Barnet had NOx reductions of 14% and Haringey decreases of 10%.
London Mayor Sadiq Khan extended the low emission zone from everywhere within the North and South Circular roads to cover all London boroughs on August 29, 2023.
The report found NOx emissions from cars and vans across the whole of outer London were estimated to be 14% lower last year than they would have been without Ulez expansion.
Particle emissions (PM2.5) from vehicle exhausts are also estimated to be 31% lower in outer London in 2024 than they would have been without the Ulez expansion.
For petrol cars to meet the Ulez requirement, they must generally have been first registered after 2005.
Most diesel cars must have been registered after September 2015 to be exempt.
The report found 96.7% of vehicles recorded as being used in outer London in September 2024 were compliant.
That is compared with 90.9% in June 2023, when plans to expand the scheme were announced.
Over the same period, the number of non-compliant vehicles detected in London on an average day fell by nearly 100,000.
Most vehicles that do not meet minimum emissions standards and do not benefit from exemptions are required to pay a £12.50 daily fee for entering the Ulez.
Mayor of London Sadiq Khan said: “The decision to expand the Ulez was not something I took lightly, but this report shows it was the right one for the health of all Londoners.
“It has been crucial to protect the health of Londoners, support children’s lung growth, and reduce the risk of people developing asthma, lung cancer and a host of other health issues related to air pollution.
“With boroughs in outer London seeing some of the biggest reductions in harmful emissions and London’s deprived communities also seeing greater benefits, this report shows why expanding Ulez London-wide was so important.”
