Informing healthy transport policies : Systematic reviews and research synthesis

Transport is an important determinant of health, and the health impact of transport interventions requires robust evaluation. Systematic reviews provide a rigorous tool for locating, appraising, and synthesizing evaluative evidence. Some systematic reviews use meta-analysis techniques to synthesize data, but other systematic reviews do not. This paper addresses some methodological and practical issues associated with conducting systematic reviews on the health impact of transport interventions. By using as case studies recently conducted reviews on topics such as the health impact of new roads and the effectiveness of interventions in promoting modal shift, the paper outlines many of the challenges faced by systematic reviewers in this field. It then describes some research synthesis techniques available to systematic reviewers and discusses some of the strengths and weaknesses of these techniques. Systematic literature reviews on the health impact of specific transport interventions can be used to inform decision making. However, reviews of such complex interventions require an innovative approach to the methodologies of systematic reviews and research synthesis.