A report released by Imperial College London earlier this week reveals that despite being “the world’s most stringent emissions zone” for pollution and air quality, the London Ultra Low Emission Zone (ULEZ) has had a minimal effect on the city’s emission levels.

The ULEZ, which was introduced in April of 2019, charges owners of fuel inefficient vehicles between £12.50 and £100 a day to operate within the zone, and was expanded last month to contain everything within the North and South Circular Roads, 18 times its original size.

Though the mayor of London, Sadiq Khan, has seen success in reducing the number of Londoners living in area with illegal levels of air pollution by up to 94%, the implementation of the ULEZ does not appear to have had as much of an impact as previously thought.

Where a previous report found that the ULEZ has reduced Nitrogen Dioxide (NO2) levels by anywhere from 13% to 37%, these new findings would suggest the actual observable impact to be less than 3%.

According to the report, the ULEZ has “caused only small improvements in air quality” over the span of its existence, but that it is most effective as “one of many policies implemented to tackle air pollution in London”, which have led to a “clearly observable” trend in cleaner air.

The study was carried out over a twelve-week period, starting in February of 2019, before the ULEZ was introduced, and ending that May.

While other cities have been considering the introduction of their own ULEZ policies, Dr. Stettler told the ICL blog that “Cities considering air pollution policies should not expect ULEZs alone to fix the issue, as they contribute only marginally to cleaner air.”

“This is especially the case for pollutants that might originate elsewhere and be blown by winds into the city, such as particulate matter and Ozone.”

When asked about his experiences with the ULEZ, London resident Aled Horner commented: “I didn’t really know the difference between congestion and ULEZ until the expansion happened. As it turns out my car is good enough for ULEZ, so the expansion ended up not really changing much for me.”

“Of course, even if it did, I would grudgingly feel positive about it – the whole point of it is to increase our health and reduce emissions after all, and the charge is a small price to pay for that.”

While Sadiq Khan has called declining air quality a “social justice issue” in the past, aiming to tackle declining health in the poorer areas of London, outlets like The Independent have reported that many in the same demographic feel the ULEZ charge disproportionately affects them.