One of TRUUD aims is to collect evidence on the impact of urban environment on health. A major component of urban environment is air pollution causing 4.2 million premature deaths per year (WHO, 2022). In many European countries, including the UK, air pollution has been central in policy debates around transport as car emissions are a major source of air pollution in urban cities.

In recent work, we have examined the impact of a new transport policy, the Low Emission Zone (LEZ) and Ultra-Low Emission Zone (ULEZ) introduced in Greater London and Central London, respectively in 2008 and 2019. These recent policies set increasingly stricter standards on vehicles, particularly targeting the most polluting ones such as older, heavier diesel-fuelled vehicles. More details on these policies are available on the IPR Policy brief.

Signs indicating Ultra Low Emission Zone (ULEZ) on a street in London, UK.

Thanks to funding from TRUUD, we assembled various sources of data to help examine the impact of the policies and eventually inform the HAUS model. Firstly, the Quarterly Labour Force Survey and the Annual Population Survey containing rich information on socio-economic characteristics of respondents, and self-reported information on physical health and well-being. Secondly, we have used administrative data from the Hospital Episode Statistics, containing all admission records of patients in English hospitals. Thirdly, we have used postcode data from Transport for London to identify areas covered by LEZ and ULEZ. Finally, we have linked in weather data from the Met Office, pollution data and other area characteristics such as house prices and the Index of Multiple Deprivation from the Office for National Statistics.

Using a quasi-experimental methodology called “Difference-in-Differences” we have been able to determine the causal impact of LEZ/ULEZ on air quality, physical health, and well-being. This methodology allows us to compare areas where the policies were introduced to similar areas without these policies, before and after the implementation of LEZ/ULEZ.

A detailed description of our results, the first in this area, is available on the IPR Policy brief. To summarise, we have found that these transport policies have significantly reduced levels of key pollutants, leading to improvements in physical health and well-being, and a reduction of hospitalisations for respiratory problems.

After the publication of the IPR Policy brief, our work has been divulgated by the University of Bath media press and has been covered by over 300 media sources, including BBC Radio 5 Live, Sky News and LBC. There has been some backlash  on X, but also some very positive tweets from Transport & Environment UK, APPG for Cycling & Walking, and UK100 amongst others.

Once published, this work will eventually feed in the evidence used by the HAUS model. Given recent news about the expansion of these policies, we are now estimating impacts on different vulnerable groups such as mothers and newly born babies, and  examining other components related to pollution such as traffic and noise. This evidence will also be used to produced heatmaps for different areas in Greater Manchester where different transport modes have been incentivised.

We very much expect the wide interest generated by our initial set of findings to continue as we expand the groups and types of pollution covered. Being part of the TRUUD programme  is helping to fill a gap in our knowledge that will eventually turn into a practical tool for decision-makers.