Why a theory and practice of change for healthy low-carbon transport is needed

The University of Birmingham’s Dr Joanne Leach, Emma Ferranti and Professors Afroditi Stathi, Simon Blainey and Chris Rogers, co-leads on the Healthy Low-carbon Transport Hub, explore how theories of change are used to support transport decision making and why a theory and practice of change that incorporates health and health inequalities is needed.

For the UK to fully decarbonise transport it must develop deeper understandings of how people’s lives are organised, and more closely match the built environment to people’s needs and the environment’s needs. Past motivations of the UK’s planning system, which variously prioritised the motorcar, the economy and urban vanity, will need to be re-evaluated. Decarbonising transport demands solutions from beyond those deliverable by the transport system, especially if those solutions are to avoid inadvertently causing disadvantage or harm.

Transport decarbonisation policy

The UK is actively planning public and private transport decarbonisation. The Department for Transport (DfT) Transport Decarbonisation Plan sets out how the UK will decarbonise its “entire transport system” through transport electrification and decreasing the use of personal motor vehicles – the latter by increasing the use of public transport and active travel (e.g., walking and cycling)1.

The Transport Decarbonisation Plan cuts the cloth in two ways. The first is by mode. Commitments include improving cycling and walking infrastructure; converting to zero-emission buses, coaches, trains, cars, planes and maritime vessels; increasing public transport passenger numbers; and decreasing road freight.

The second is across modes. Commitments include decarbonising the freight and logistics sector; embedding decarbonised transport in spatial planning; encouraging alternative and low-carbon fuels; and encouraging research, innovation and development in transport decarbonisation.

Transport, health and health inequality

For the UK to meet its emissions targets it must accelerate transport decarbonisation whilst, ideally, maximising health co-benefits and reducing health inequalities (or, at the very least, not making them worse). However, the UK’s record in this regard is mixed. Perhaps the best-known example is the lowering of diesel vehicle tax in 2001, known as the ‘dash for diesel’. This low-carbon policy encouraged the use of ‘cleaner’ diesel vehicles as measured by carbon emissions. It was successful in increasing the number of diesel vehicles on the road and thus reducing carbon emissions, but it was unsuccessful in improving air quality because diesel engines produce higher levels of particulate matter and other pollutants2. Unsurprisingly, adverse health outcomes followed3,4.

Almost 25 years later the Government’s promotion of electric vehicles (EVs) risks repeating the exacerbation of unintended consequences as happened with the ‘dash for diesel’. Tax breaks and air quality zone fee exceptions have been successful in encouraging electric vehicle uptake as a low-carbon emission solution, although the introduction of a pay-per-mile system and the removal of the Vehicle Excise Duty exemption in the 2026 budget may slow future uptake. Research is revealing a nuanced picture regarding the impact of EVs. Although EVs do not directly contribute to tail pipe emissions they do contribute to congestion, and thereby to localised air pollution where congestion forms. The heavier weight and faster acceleration/deceleration of EVs are leading to increased particulate matter pollution from tyre and road surface wear that puts EVs almost on par with petrol vehicles for overall air pollution5,6 whilst simultaneously increasing injury severity in collisions7. It is too early to fully assess how the uptake of EVs will affect population health and health equity, but it is not too early to see that there could be negative impacts on both if adjustments beyond taxes are not made.

Shifting public understanding and behaviour for low-carbon transport

The need to inform and engage the public on the health benefits of low-carbon transport choices is critical. While environmental arguments for decarbonisation dominate current discourse, public opinion remains divided on the extent of environmental gains (for example, mineral extraction and battery recycling are polemical). This uncertainty can undermine support for low-carbon policies and interventions. Research shows that framing climate action not only as a way to protect the planet but also as an opportunity to improve personal and family health makes the message far more compelling8,9,10,11.

If done right, low-carbon transport interventions—such as active travel, improved public transport, and reduced car dependency—deliver tangible health benefits. These include improved air quality, reduced risk of chronic diseases through increased physical activity, and safer, more liveable streets12,13. These have the potential to outweigh short-term health disbenefits, such as increased exposure to viruses on public transport14. Communicating the benefits and disbenefits clearly and consistently can help shift perceptions from ‘net zero as an abstract climate goal’ to ‘net zero as a pathway to better health and wellbeing’.

For example, highlighting that walking and cycling infrastructure reduces cardiovascular risk, or that cleaner air can prevent respiratory illnesses in children, makes the case for change relatable and urgent. Robust evidence linking transport decarbonisation to health outcomes should be central to public messaging campaigns, community engagement strategies, and policy narratives15. By reframing net zero as a health-positive transformation, policymakers can build stronger public support and encourage adoption of low-carbon transport choices.

There exist, though, gaps and tensions in evidence on low-carbon transport solutions and their health impacts. To address these, the UK Government, through UK Research and Innovation (UKRI), has funded a major new initiative, the Healthy Low-carbon Transport Hub. This five-year, multi-university hub has been established to ensure the UK’s low-carbon transport investments improve health and health equity outcomes. It is providing policymakers and transport decision makers with the evidence needed to modify transport decarbonisation interventions to maximise health and health equity.

Transport decision making and theories of change

The Transport Decarbonisation Plan sets targets for reaching net zero and identifies actions intended to ensure the targets are achieved. It is complemented by DfT’s Transport Analysis Guidance on evaluating the impacts of transport interventions16. Theories of change are key components of the guidance but are restricted to assessing individual transport solutions. Transport is, however, a large socio-technical system encompassing complex interdependences and multiple scales. A comprehensive and system-wide approach is therefore needed, and especially so if health co-benefits are to be realised. Placing individuals at the centre of transport systems (their mobilities, motivations, values, accessibilities, affordabilities, capabilities and attitudes) has the potential to clash with the more traditional ‘top-down’ infrastructure provision of recent decades founded on assumed societal needs and wants, but this need not be the case.

The Healthy Low-carbon Transport Hub is developing a theory of change that looks beyond single transport solutions to embed long-term, systemic transformation. By linking transport interventions to wider system shifts and mapping the causal pathways, it aims to show how healthy, low-carbon transport can be delivered at scale.

The theory of change will be complemented by a practical framework designed to turn strategy into delivery and to transform business as usual. This practice of change will consolidate evidence from the Hub’s research on real-world, low-carbon transport and transport-related interventions such as low-traffic neighbourhoods, mobility hubs, clean air zones and homeworking. It will also integrate insights from innovative, co-designed interventions tested in UKCRIC’s state-of-the-art Person-Environment-Action Research Laboratory (PEARL) and applied in the real world. By showcasing tested design options for resilience, sustainability and liveability, the theory and practice of change will equip policy makers and practitioners with actionable guidance to accelerate low-carbon transport adoption and embed health equity into decision making.

The second is across modes. Commitments include decarbonising the freight and logistics sector; embedding decarbonised transport in spatial planning; encouraging alternative and low-carbon fuels; and encouraging research, innovation and development in transport decarbonisation.

Transport, health and health inequality

For the UK to meet its emissions targets it must accelerate transport decarbonisation whilst, ideally, maximising health co-benefits and reducing health inequalities (or, at the very least, not making them worse). However, the UK’s record in this regard is mixed. Perhaps the best-known example is the lowering of diesel vehicle tax in 2001, known as the ‘dash for diesel’. This low-carbon policy encouraged the use of ‘cleaner’ diesel vehicles as measured by carbon emissions. It was successful in increasing the number of diesel vehicles on the road and thus reducing carbon emissions, but it was unsuccessful in improving air quality because diesel engines produce higher levels of particulate matter and other pollutants2. Unsurprisingly, adverse health outcomes followed3,4.

Almost 25 years later the Government’s promotion of electric vehicles (EVs) risks repeating the exacerbation of unintended consequences as happened with the ‘dash for diesel’. Tax breaks and air quality zone fee exceptions have been successful in encouraging electric vehicle uptake as a low-carbon emission solution, although the introduction of a pay-per-mile system and the removal of the Vehicle Excise Duty exemption in the 2026 budget may slow future uptake. Research is revealing a nuanced picture regarding the impact of EVs. Although EVs do not directly contribute to tail pipe emissions they do contribute to congestion, and thereby to localised air pollution where congestion forms. The heavier weight and faster acceleration/deceleration of EVs are leading to increased particulate matter pollution from tyre and road surface wear that puts EVs almost on par with petrol vehicles for overall air pollution5,6 whilst simultaneously increasing injury severity in collisions7. It is too early to fully assess how the uptake of EVs will affect population health and health equity, but it is not too early to see that there could be negative impacts on both if adjustments beyond taxes are not made.

Shifting public understanding and behaviour for low-carbon transport

The need to inform and engage the public on the health benefits of low-carbon transport choices is critical. While environmental arguments for decarbonisation dominate current discourse, public opinion remains divided on the extent of environmental gains (for example, mineral extraction and battery recycling are polemical). This uncertainty can undermine support for low-carbon policies and interventions. Research shows that framing climate action not only as a way to protect the planet but also as an opportunity to improve personal and family health makes the message far more compelling8,9,10,11.

If done right, low-carbon transport interventions—such as active travel, improved public transport, and reduced car dependency—deliver tangible health benefits. These include improved air quality, reduced risk of chronic diseases through increased physical activity, and safer, more liveable streets12,13. These have the potential to outweigh short-term health disbenefits, such as increased exposure to viruses on public transport14. Communicating the benefits and disbenefits clearly and consistently can help shift perceptions from ‘net zero as an abstract climate goal’ to ‘net zero as a pathway to better health and wellbeing’.

For example, highlighting that walking and cycling infrastructure reduces cardiovascular risk, or that cleaner air can prevent respiratory illnesses in children, makes the case for change relatable and urgent. Robust evidence linking transport decarbonisation to health outcomes should be central to public messaging campaigns, community engagement strategies, and policy narratives15. By reframing net zero as a health-positive transformation, policymakers can build stronger public support and encourage adoption of low-carbon transport choices.

There exist, though, gaps and tensions in evidence on low-carbon transport solutions and their health impacts. To address these, the UK Government, through UK Research and Innovation (UKRI), has funded a major new initiative, the Healthy Low-carbon Transport Hub. This five-year, multi-university hub has been established to ensure the UK’s low-carbon transport investments improve health and health equity outcomes. It is providing policymakers and transport decision makers with the evidence needed to modify transport decarbonisation interventions to maximise health and health equity.

Transport decision making and theories of change

The Transport Decarbonisation Plan sets targets for reaching net zero and identifies actions intended to ensure the targets are achieved. It is complemented by DfT’s Transport Analysis Guidance on evaluating the impacts of transport interventions16. Theories of change are key components of the guidance but are restricted to assessing individual transport solutions. Transport is, however, a large socio-technical system encompassing complex interdependences and multiple scales. A comprehensive and system-wide approach is therefore needed, and especially so if health co-benefits are to be realised. Placing individuals at the centre of transport systems (their mobilities, motivations, values, accessibilities, affordabilities, capabilities and attitudes) has the potential to clash with the more traditional ‘top-down’ infrastructure provision of recent decades founded on assumed societal needs and wants, but this need not be the case.

The Healthy Low-carbon Transport Hub is developing a theory of change that looks beyond single transport solutions to embed long-term, systemic transformation. By linking transport interventions to wider system shifts and mapping the causal pathways, it aims to show how healthy, low-carbon transport can be delivered at scale.

The theory of change will be complemented by a practical framework designed to turn strategy into delivery and to transform business as usual. This practice of change will consolidate evidence from the Hub’s research on real-world, low-carbon transport and transport-related interventions such as low-traffic neighbourhoods, mobility hubs, clean air zones and homeworking. It will also integrate insights from innovative, co-designed interventions tested in UKCRIC’s state-of-the-art Person-Environment-Action Research Laboratory (PEARL) and applied in the real world. By showcasing tested design options for resilience, sustainability and liveability, the theory and practice of change will equip policy makers and practitioners with actionable guidance to accelerate low-carbon transport adoption and embed health equity into decision making.

Contact us

If you would like to be involved in this research, kept informed of the Hub’s activities and for any other enquiries, please contact Tim Yates, Marketing, Communications and Events Manager, on tim.j.yates@ucl.ac.uk

References

  1. DfT (2021) Decarbonising transport: A better, greener Britain. Available at: https://www.gov.uk/government/publications/transport-decarbonisation-plan
  2. BBC (2017). Why officials in Labour government pushed ‘dash for diesel’. Available at: https://www.bbc.co.uk/news/uk-politics-41985715
  3. EEA (2016). Air quality in Europe 2016 report. Available at: https://www.eea.europa.eu/en/analysis/publications/air-quality-in-europe-2016
  4. S. Kahn (2017). Fact Check: are diesel cars really more polluting than petrol cars? Available at: https://theconversation.com/fact-check-are-diesel-cars-really-more-polluting-than-petrol-cars-76241
  5. V. R. J. H. Timmers, P. A. J. Achten (2016). Non-exhaust PM emissions from electric vehicles. DOI: 10.1016/j.atmosenv.2016.03.017. Available at: https://www.sciencedirect.com/science/article/abs/pii/S135223101630187X
  6. M.Y. Fares, A. Albdour, M. Lanotte (2024). Evaluation of potential electric vehicles load-induced damage on flexible pavements. DOI: 10.1016/j.trd.2024.104475. Available at: https://www.sciencedirect.com/science/article/abs/pii/S1361920924004322
  7. P. J. Edwards, S. Moore, C. Higgins (2024). Pedestrian safety on the road to net zero: cross-sectional study of collisions with electric and hybrid-electric cars in Great Britain. DOI: 10.1136/jech-2024-221902. Available at: https://jech.bmj.com/content/78/8/487
  8. A. H. Sinclair et al. (2025). Behavioral interventions motivate action to address climate change. Available at: https://www.pnas.org/doi/pdf/10.1073/pnas.2426768122
  9. N. Dasandi et al. (2022). Positive, global, and health or environment framing bolsters public support for climate policies. Available at: https://www.nature.com/articles/s43247-022-00571-x
  10. J.  Tielen (2025). Health is the popular twin of climate action—use it for benefits across the board. Available at: https://impact.economist.com/health-society/health-is-the-popular-twin-of-climate-action-use-it-for-benefits-across-the-board
  11. World Health Organisation (2024). Communicating on climate change and health: Toolkit for health professionals. Available at: https://www.who.int/publications/i/item/9789240090224
  12. WHO (2024). Promoting healthy active mobility. Available at: https://www.who.int/europe/activities/promoting-healthy-active-mobility
  13. Health Foundation (2024). Health benefits of walking and cycling: preventable early deaths. Available at: https://www.health.org.uk/evidence-hub/transport/active-travel/health-benefits-of-walking-and-cycling-preventable-early
  14. J. Troko et al. (2011). Is public transport a risk factor for acute respiratory infection?. Available at: https://link.springer.com/article/10.1186/1471-2334-11-16
  15. L. Moutet et al. (2025). The public health co-benefits of strategies consistent with net-zero emissions: a systematic review. Available at: https://climahealth.info/wp-content/uploads/2025/07/PIIS2542519624003309-1.pdf
  16. DfT (2022). Transport analysis guidance: Unit E1: Evaluation. Available at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1126369/TAG_Unit_E1_-_Evaluation_Nov_2022_v1.0.pdf

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