Ex Post Evaluation and Relevance to Decision-making

Decision making for transport infrastructure planning relies heavily on various types of impact assessment, typically centred on construction cost estimates and travel demand forecasts. However, when comparing ex-ante appraisals with ex-post evaluations of completed projects, neither cost estimates nor demand forecasts appear particularly accurate. This paper discusses the available research on ex-post evaluations. The paper identifies five key issues and presents recommendations for improving appraisal practice.