Children living in London’s ultra-low emission zone (Ulez) were almost four times as likely to switch to travelling to school by cycling, walking or scootering than those residing outside the area, new research has found.

A University of Cambridge study, published on Wednesday, examined 2,000 children aged six to nine across 84 primary schools in London and Luton.

The Ulez, which requires motor vehicles that do not meet minimum emissions standards or are exempt to pay a £12.50 daily fee for entering the zone, was introduced by London Mayor Sadiq Khan in April 2019 to improve air quality in the city and was expanded to cover all London boroughs in August 2023.

The research compiled data from June 2018 to April 2019, before the Ulez was introduced, and after its implementation – between June 2019 to March 2020.

It found about four in ten (42%) children living in London who travelled by car prior to the introduction of the Ulez switched to active modes of transport, defined as walking, cycling or scootering during any part of their route to school, after the zone was implemented.

During the same period, only two in ten children living in Luton, outside the Ulez zone, had swapped journeying to school by car for active transport methods.

The study, led by Dr Christina Xiao, noted that children living further from school in London were more likely to change to active transport and that the Ulez had no effect on those living closer to school.

The research highlights the negative impact travelling by car has on children’s physical health, including “sedentary behaviour” and asthma linked to air pollution, as well as the positive mental and physical health benefits of cycling, walking and scootering.

Government guidelines recommend that children do 60 minutes of moderate to vigorous exercise daily, but research found less than half of children did this in 2021, the study emphasises.

According to a Greater London Authority air quality report, published in March 2024, more than 95% of vehicles driving in the capital are compliant with Ulez emissions standards, up from 39% in 2017.

In July 2024, City Hall said its data showed the Ulez expansion has been successful in driving down emissions and that London’s roadside air quality is improving at a faster rate, on average, than the rest of England.

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.