Health Co-Benefits of Policies to Mitigate Climate Change in the Transport Sector: Systematic Review

Abstract

Background Theory, common sense and modelling studies suggest that some interventions to mitigate greenhouse gas (GHG) emissions in the transport sector can, in addition to the long term benefits from stabilising the global climate, have substantial short term benefits for population health. Policies that encourage active modes of transportation, for example, may increase population physical activity or decrease air pollution exposure. This can reduce the population burden of a number of conditions including some cancers, diabetes, heart disease and dementia. We reviewed the evidence on whether policies that decrease transport sector GHG emissions have a measurable effect on health determinants, population health and/or health inequalities under ‘real world’ conditions. Methods Design: Systematic review. Data sources: We included published and unpublished reports, identified from searching 12 electronic databases, reference lists, existing reviews, websites and contacting experts in the field. Eligibility: Observational or experimental studies with a control group and time series studies were included. Studies were included if they examined a ‘real life’ intervention/policy/natural experiment in the transport sector, and measured health behaviours or outcomes, and calculated GHG emission change. Results We included 22 studies of 11 interventions in four countries. Most studies were of quasi-experimental design and published in the grey literature. Eight were interventions of personalised travel planning, two involved legislative changes (one to enable a congestion charge in Stockholm, one a ‘cash-out’ of employee parking benefits), and one was a multifaceted intervention in three towns to promote sustainable modes of travel. Studies were focused on land transport only and almost exclusively on policies that try to change individual behaviour. There was little assessment of how these interventions could impact on health inequalities. All studies reported decreases in GHG emissions as a result of their interventions; however methods to assess emission changes varied in robustness. Health benefits reported from the studies included modest increases in physical activity (for example an average increase of two to three minutes a day walking for transport purposes) and reductions in mortality from air pollution. Study quality, with one exception, was poor. Conclusions Research quality urgently needs to improve, as does the breadth of the types of interventions studied. There are exciting opportunities for innovative study designs and methodologies to answer research questions in this important area. The need for public health practitioners to work more closely with the transport sector is paramount.