The scope of meta-analysis for transport policy impact analysis in environmental economics

Meta-analysis offers an analytical framework for research synthesis based on a comparative study of research findings undertaken by different researchers. In this paper, we investigate the possibilities of applying meta-analysis to transport policy impact studies in environmental-economics. The heterogeneity of studies in this field however makes it difficult to apply meta-analysis directly. We therefore propose a general equilibrium framework as a benchmark for comparison, and as a synthesis of the research findings we obtain from studies underlying a meta-analysis. A meta-analysis of studies results in decision rules that obtain the environmental impact of a transport policy as a function of the characteristics of these studies, i.e. variations in environmental impact of the transport policy can be attributed to variations in specific char-acteristics of these studies. The transport policy impact studies underlying a meta-analysis in environmental economics can be seen to derive their characteristics from a common general equilibrium framework. This framework leads to a classification of all possible characteristics of transport impact studies, that can be used as a basis for several types of meta-analytic methods to distinguish the most relevant ones among them. Policy makers can then improve the effectivity of their policies by concentrating on these relevant characteristics.