Objective To assess the effects of interventions to promote walking in individuals and populations. Design Systematic review. Data sources Published and unpublished reports in any language identified by searching 25 electronic databases, by searching websites, reference lists, and existing systematic reviews, and by contacting experts. Review methods Systematic search for and appraisal of controlled before and after studies of the effects of any type of intervention on how much people walk, the distribution of effects on walking between social groups, and any associated effects on overall physical activity, fitness, risk factors for disease, health, and wellbeing.

Objectives To assess what interventions are effective in promoting a population shift from using cars towards walking and cycling and to assess the health effects of such interventions. Data sources Published and unpublished reports in any language identified from electronic databases, bibliographies, websites, and reference lists. Review methods Systematic search and appraisal to identify experimental or observational studies with a prospective or controlled retrospective design that evaluated any intervention applied to an urban population or area by measuring outcomes in members of the local population. Results 22 studies met the inclusion criteria. We found some evidence that targeted behaviour change programmes can change the behaviour of motivated subgroups, resulting (in the largest study) in a shift of around 5% of all trips at a population level. Single studies of commuter subsidies and a new railway station also showed positive effects. The balance of best available evidence about publicity campaigns, engineering measures, and other interventions suggests that they have not been effective. Participants in trials of active commuting experienced short term improvements in certain measures of health and fitness, but we found no good evidence on effects on health of any effective intervention at population level. Conclusions The best available evidence of effectiveness in promoting a modal shift is for targeted behaviour change programmes, but the social distribution of their effects is unclear and some other types of intervention have yet to be rigorously evaluated.

Objective To assess the effects of major multi-sport events on health and socioeconomic determinants of health in the population of the city hosting the event. Design Systematic review.

Study objective: There is little guidance on how to identify useful evidence about the health effects of social interventions. The aim of this study was to assess the value of different ways of finding this type of information. Design: Retrospective analysis of the sources of studies for one systematic review. Setting: Case study of a systematic review of the effectiveness of interventions in promoting a population shift from using cars towards walking and cycling. Main results: Only four of the 69 relevant studies were found in a ''first-line'' health database such as Medline. About half of all relevant studies were found through the specialist Transport database. Nine relevant studies were found through purposive internet searches and seven relevant studies were found by chance. The unique contribution of experts was not to identify additional studies, but to provide more information about those already found in the literature. Conclusions: Most of the evidence needed for this review was not found in studies indexed in familiar literature databases. Applying a sensitive search strategy across multiple databases and interfaces is very labour intensive. Retrospective analysis suggests that a more efficient method might have been to search a few key resources, then to ask authors and experts directly for the most robust reports of studies identified. However, internet publications and serendipitous discoveries did make a significant contribution to the total set of relevant evidence. Undertaking a comprehensive search may provide unique evidence and insights that would not be obtained using a more focused search.T here are frequent calls for better evidence about the effects of interventions to improve population health.

Study objective: There is little guidance on how to select the best available evidence of health effects of social interventions. The aim of this paper was to assess the implications of setting particular inclusion criteria for evidence synthesis. Design: Analysis of all relevant studies for one systematic review, followed by sensitivity analysis of the effects of selecting studies based on a two dimensional hierarchy of study design and study population. Setting: Case study of a systematic review of the effectiveness of interventions in promoting a population shift from using cars towards walking and cycling. Main results: The distribution of available evidence was skewed. Population level interventions were less likely than individual level interventions to have been studied using the most rigorous study designs; nearly all of the population level evidence would have been missed if only randomised controlled trials had been included. Examining the studies that were excluded did not change the overall conclusions about effectiveness, but did identify additional categories of intervention such as health walks and parking charges that merit further research, and provided evidence to challenge assumptions about the actual effects of progressive urban transport policies. Conclusions: Unthinking adherence to a hierarchy of study design as a means of selecting studies may reduce the value of evidence synthesis and reinforce an ''inverse evidence law'' whereby the least is known about the effects of interventions most likely to influence whole populations. Producing generalisable estimates of effect sizes is only one possible objective of evidence synthesis. Mapping the available evidence and uncertainty about effects may also be important. D espite increasing calls for systematic reviews of health effects of social interventions, there is little methodological research or even guidance on how such reviews should be done. We have lifted the lid on the ''private life'' of the input side of one such systematic review to expose some of our methodological processes and decisions to critical analysis.1 In a companion paper, we set the scene and examined one phase of the review, the search for evidence. 2In this paper, we examine another phase of the review: the selection of evidence for inclusion. We investigate the effect of varying our inclusion criteria on the findings and overall value of the review. SELECTING EVIDENCE FOR INCLUSIONResearchers designing systematic reviews of intervention studies are advised to specify their research questions in terms of four facets: the intervention, the population receiving the intervention, the outcome of interest, and the study designs deemed worthy of inclusion.3 This approach is undoubtedly helpful for structuring research questions and protocols, but we aimed to synthesise population level evidence in a cross disciplinary field where comparatively little empirical intervention research has been done. A broad understanding of population health and its wider determinants implied a...