How London’s Ultra Low Emission Zone is changing the school run

London’s Ultra Low Emission Zone (ULEZ) is transforming children’s journeys to school by making streets safer, improving perceptions of air quality and encouraging children to live healthier lives. A new study published today in BMJ Open, and funded by the National Institute for Health and Care Research (NIHR), highlights its benefits, with many families noticing cleaner air and safer roads. However, it also reveals challenges, particularly for those living in outer boroughs who are more reliant on the car and may struggle to adapt.

Road traffic is a major source of air pollution in London, posing serious health risks. One in 11 children in the city has asthma, a condition worsened by poor air quality. Car use also limits opportunities for active travel, such as walking and cycling, which help prevent obesity and chronic illness.

Introduced in 2019, the ULEZ charges high-polluting vehicles that enter all London boroughs. According to Transport for London (TfL), it has reduced levels of the pollutant nitrogen dioxide (NO₂) by 53% in central London, 24% in inner London, and 21% in outer London, while also cutting traffic.

The research published today in BMJ Open — led by scientists from the University of Cambridge and Queen Mary University of London — examines the ULEZ’s impact on school travel. This work is part of the Children’s Health in London and Luton (CHILL) Study, which previously found that 42% of children who travelled by car switched to active travel modes after the ULEZ was introduced. Through in-depth interviews with 21 families from the CHILL study and seven teachers from CHILL schools, the researchers identified key drivers of change and ongoing challenges in adapting to the policy.

Families reported the rising costs of car travel and reduced convenience made active travel more appealing. Those who already walked or cycled discussed how improved air quality made the journey more enjoyable and healthier. With less traffic, some families took longer scenic routes home, which meant they spent more time together being active. Teachers observed fewer asthma related symptoms among students and noted that safer streets encouraged more outdoor play.

Despite its benefits, adapting to the ULEZ has been hard for many families outside central London. The scrappage scheme helped some families to upgrade their vehicles, but it was not enough to fully cover the cost of a new ULEZ compliant car. Public transport was often described as expensive or poorly connected in these areas. Some families parked outside the zone and walked, while others felt forced to continue driving as it remained the most affordable and convenient option. The study highlights inequalities in access to cleaner, greener travel, calling for faster investment in affordable, well-connected transport options across all boroughs.

Dr Olivia Alliott, lead author from the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge, said: "Policies like the ULEZ play a crucial role in promoting a healthier school journey for many families. However, a fundamental part of their success is making sure that everyone experiences these benefits by ensuring such policies are implemented alongside accessible and affordable alternatives to driving.

“Our previous work found that the ULEZ has encouraged children to take up walking and cycling to school. This work identifies some of the possible reasons for that, and highlights both the positive and negative experiences of the ULEZ which are reflected in an individual’s ability to pay the charge and the alternative travel modes available”

The study reinforces the importance of policies like the ULEZ in shaping healthier, sustainable cities while also ensuring that solutions are inclusive and equitable. It offers valuable insights for policymakers worldwide considering similar initiatives to improve air quality and public health.

Joint senior author Professor Chris Griffiths from the Wolfson Institute of Population Health, Queen Mary University of London, said: “This important study brings yet another perspective telling us how the ULEZ can affect the way families can live, travel and experience the environment. These systemic effects on society go beyond simply ‘cleaning the city air’”

The interviews were conducted between November 2022 and March 2023, and the results do not include experiences of the ULEZ expansion in August 2023 to cover the majority of Greater London.

The study was funded by the National Institute for Health and Care Research (NIHR), NIHR Applied Research Collaboration North Thames and the Medical Research Council. The study was conducted in collaboration with Queen Mary University of London, Imperial College London, University of Bedfordshire, University of Exeter, University of Edinburgh, University of Oxford and University of Southern California.

Reference

Alliott, O, et al. London’s Ultra Low Emission Zone and active travel to school: a qualitative study exploring the experiences of children, families and teachers. BMJ Open; 03 March 2025; DOI:10.1136/bmjopen-2024-091929

ENDS

Contact details

Dr Paul Browne
Senior Communications Manager
MRC Epidemiology Unit

University of Cambridge
Tel: +44 (0)1223 763381

Mob: +44 (0)7991 536387
Email:paul.browne@mrc-epid.cam.ac.uk

A copy of the paper under embargo is available on request.

About the University of Cambridge

The University of Cambridge is one of the world’s leading universities, with a rich history of radical thinking dating back to 1209. Its mission is to contribute to society through the pursuit of education, learning and research at the highest international levels of excellence.

The University comprises 31 autonomous Colleges and over 100 departments, faculties and institutions. Its 24,000 students include around 9,000 international students from 147 countries. In 2023, 73% of its new undergraduate students were from state schools and more than 25% from economically disadvantaged backgrounds.

Cambridge research spans almost every discipline, from science, technology, engineering and medicine through to the arts, humanities and social sciences, with multi-disciplinary teams working to address major global challenges. In the Times Higher Education’s rankings based on the UK Research Excellence Framework, the University was rated as the highest scoring institution covering all the major disciplines.

A 2023 report found that the University contributes nearly £30 billion to the UK economy annually and supports more than 86,000 jobs across the UK, including 52,000 in the East of England. For every £1 the University spends, it creates £11.70 of economic impact, and for every £1 million of publicly-funded research income it receives, it generates £12.65 million in economic impact across the UK.

The University sits at the heart of the ‘Cambridge cluster’, in which more than 5,000 knowledge-intensive firms employ more than 71,000 people and generate £21 billion in turnover. Cambridge has the highest number of patent applications per 100,000 residents in the UK.

www.cam.ac.uk

About the MRC Epidemiology Unit

The MRC Epidemiology Unit is a department at the University of Cambridge. It is working to improve the health of people in the UK and around the world. Obesity, type 2 diabetes and related metabolic disorders present a major and growing global public health challenge. These disorders result from a complex interplay between genetic, developmental, behavioural and environmental factors that operate throughout life. The mission of the Unit is to investigate the individual and combined effects of these factors and to develop and evaluate strategies to prevent these diseases and their consequences. www.mrc-epid.cam.ac.uk

About the Medical Research Council

The Medical Research Council is at the forefront of scientific discovery to improve human health. Founded in 1913 to tackle tuberculosis, the MRC now invests taxpayers’ money in some of the best medical research in the world across every area of health. Thirty-three MRC-funded researchers have won Nobel prizes in a wide range of disciplines, and MRC scientists have been behind such diverse discoveries as vitamins, the structure of DNA and the link between smoking and cancer, as well as achievements such as pioneering the use of randomised controlled trials, the invention of MRI scanning, and the development of a group of antibodies used in the making of some of the most successful drugs ever developed. Today, MRC-funded scientists tackle some of the greatest health problems facing humanity in the 21st century, from the rising tide of chronic diseases associated with ageing to the threats posed by rapidly mutating micro-organisms. The Medical Research Council is part of UK Research and Innovation. https://mrc.ukri.org/

About Queen Mary University of London  

At Queen Mary University of London, we believe that a diversity of ideas helps us achieve the previously unthinkable.  

Throughout our history, we’ve fostered social justice and improved lives through academic excellence. And we continue to live and breathe this spirit today, not because it’s simply ‘the right thing to do’ but for what it helps us achieve and the intellectual brilliance it delivers.    

Our reformer heritage informs our conviction that great ideas can and should come from anywhere. It’s an approach that has brought results across the globe, from the communities of east London to the favelas of Rio de Janeiro.    

We continue to embrace diversity of thought and opinion in everything we do, in the belief that when views collide, disciplines interact, and perspectives intersect, truly original thought takes form.   

www.qmul.ac.uk     

The National Institute for Health and Care Research (NIHR)

The mission of the National Institute for Health and Care Research (NIHR) is to improve the health and wealth of the nation through research. We do this by:

• Funding high quality, timely research that benefits the NHS, public health and social care;
• Investing in world-class expertise, facilities and a skilled delivery workforce to translate discoveries into improved treatments and services;
• Partnering with patients, service users, carers and communities, improving the relevance, quality and impact of our research;
• Attracting, training and supporting the best researchers to tackle complex health and social care challenges;
• Collaborating with other public funders, charities and industry to help shape a cohesive and globally competitive research system;
• Funding applied global health research and training to meet the needs of the poorest people in low and middle income countries.

NIHR is funded by the Department of Health and Social Care. Its work in low and middle income countries is principally funded through UK Aid from the UK government.