What is the ULEZ?

The ULEZ is an area of London that drivers of high-polluting vehicles have to pay a charge to drive in. The idea—designed to reduce air pollution as well as congestion—was initially proposed by a Conservative, Boris Johnson, in 2015 when he served as mayor. It was implemented by Khan in 2019 in inner London, expanded to border the capital’s North Circular and South Circular roads in 2021, then enlarged again in August 2023 to cover all of greater London. 

How does it operate?

Users of vehicles that don’t meet specified standards on emissions of nitrogen oxide and particulate matter have to pay to drive in the zone and face fines of as much as £180 if they don’t. Most gasoline-powered cars manufactured since 2006 are compliant, as are most diesel cars made since September 2016. The zone operates 24 hours a day, every day except Christmas. 

Is it working?

Emissions of nitrogen oxides, or NOX, within the North and South Circular were cut by 26% between 2019 and 2022, according to a progress report published in February 2023. Nitrogen dioxide levels were 46% lower in central London than they would have been without the policy, while output of particulate matter known as PM2.5s dropped by 19%. Transport for London said in October that 95% of vehicles across inner and outer London were now compliant with clean-air standards. “I’ve been measuring air pollution in London for 30 years, and it is hard to think of another urban-scale policy that has been as effective as the central and inner London ULEZ,” said Gary Fuller, an air pollution scientist at Imperial College London.

Why is the ULEZ controversial?

The enlargement of ULEZ beyond the city’s core meant it covered outlying boroughs, where more people own cars, public transport is scarcer, and the urban landscape has been designed over decades to prioritize road travel. Khan’s critics said the ULEZ impose extra charges on those motorists who can least afford them amid the post-pandemic cost-of-living crisis. While studies suggest the climate and the environment are among top issues for U.K. voters, many resent being hit with financial penalties aimed at forcing them to adopt a greener lifestyle. 

What did the mayor do in response?

Khan boosted the value of a scrappage program to help poorer people replace their old cars with newer ones, allowing Londoners with cars that aren’t compliant with the ULEZ rules to receive a £2,000 grant for upgrading their vehicles. Small businesses were able to receive up to £21,000 to scrap as many as three vans. 

What’s been the political impact of the ULEZ?

A special election in July 2023 to replace Johnson in his parliamentary seat of Uxbridge and South Ruislip turned into a referendum on the ULEZ expansion. Prime Minister Rishi Sunak’s Conservatives seized on the issue, with the local Tory candidate presenting himself as the “Stop ULEZ” option, even though the matter is within the remit of London’s City Hall and not the national parliament. In the end, the Tories unexpectedly held Johnson’s old seat. Three months later, Sunak watered down his government’s green agenda, saying current policies to tackle climate change risked “losing the consent of the British people.” Khan’s rivals are tapping into anti-ULEZ sentiment once again in the run-up to mayoral and local government elections in May, with Khan’s Conservative opponent Susan Hall vowing to reverse the expansion if she wins. Khan’s office said such a move would have little impact on motorists because 95% of vehicles on the city’s roads are now ULEZ-compliant and don’t pay the daily charge. 

How popular is the ULEZ?

A February survey by campaign group Clean Air Wins found 46% of Londoners supported the ULEZ before it covered where they lived, and support rose to 53% once their area was included in the charging zone.