Impacts of transport on sustainability: Towards an integrated transatlantic evidence base

Despite a large body of literature on the negative impacts and externalities of transport systems, it is difficult for policy-makers to infer a coherent message about whether intervention should be considered, and if so, how to weigh the relative importance of multiple domains of impact. This paper examines the extent to which the results of research on the impacts of transport in the European Union (EU), the USA and Canada have been translated into improved public policy on sustainable development. Over 3 years, approximately 100 researchers contributed to a review that focused primarily on the environment, safety, public health, land use and congestion. There were findings on four main issues. First, the understanding of impacts is uneven and, with some notable exceptions, poorly integrated: in particular, where there is no real commitment to internalizing costs, there is little incentive to develop assessment frameworks that support decisions about tradeoffs between costs ( and benefits) in multiple domains. Second, the sustainability of transport is often viewed from the policy side as something that has to be 'set off' against affordability, equity and acceptability in a calculus that often treats transport in isolation: a broader view of sustainability might better help identify ways that transport can contribute to a decoupling of economic growth from a growth in impacts. Third, some important gaps in the research base were identified. Broad in nature, they concerned longer-term trajectories, societal learning, increased attention to freight and policy implementation. Finally, activities are suggested to improve the organization of a transatlantic evidence base that benefits from appropriately scaled comparisons between regions of Europe and North America, and which respects the complexity of impact domains and their interactions. The highest priority was given to cross-national analyses of transport and land-use policies relevant to sustainability, and to holistic evaluations of actual implementations of 'wise' policy packages in urban regions.