A preliminary and evolving conceptual model (see next figure) was developed and debated during a workshop held in Barcelona November 9th-11th 2009. Forty five international experts from 29 institutes/research groups and 12 different countries attended the meeting, reviewing the state of the art knowledge and discussing strengths and limitations of evidence of different linkages between urban and transportation policies, exposures and public health, to determine the relevance and appropriateness of exposures, outcomes, and exposure-response functions to be included in a quantitative assessment of health impacts of active travel policies.
The workshop concluded that evaluating impacts of active travel policies is highly complex; however, many associations can be quantified. Identifying health-maximizing policies and conditions requires integrated HIAs. Policies that increase active travel are likely to generate large individual health benefits through increases in physical activity for active travelers. Smaller, but population-wide benefits could accrue through reductions in air and noise pollution. Depending on conditions of policy implementations, risk tradeoffs are possible for some individuals who shift to active travel and consequently increase inhalation of air pollutants and exposure to traffic injuries. Well-designed policies may enhance health benefits through indirect outcomes such as improved social capital and diet, but these synergies are not sufficiently well understood to allow quantification at this time.
A review article of health impacts of active transportation policies was published as an outcome of the workshop:
de Nazelle, A., MJ Nieuwenhuijsen, JM Antó, M Brauer, D Briggs, C Braun-Fahrlander, N Cavill, AR Cooper, H Desqueyroux, S Fruin, G Hoek, LI Panis, N Janssen, M Jerrett, M Joffe, ZJ Andersen, E van Kempen, S Kingham, N Kubesch, K Leyden, JD Marshall, J Matamala, G Mellios, M Mendez, H Nassif, D Ogilvie, R Peiró, K Pérez, A Rabl, M Ragettli, D Rodríguez, D Rojas, P Ruiz, JF Sallis, J Terwoert, JF Toussaint, J Tuomisto, M Zuurbier, E Lebret, (2011) Improving health through policies that promote active travel: a review of evidence to support integrated health impact assessment. Environment International 37: 766-777.
Next figure is a conceptual model of active transport policies and possible health impacts.