Aalborg Universitet Forecasts: Fact or Fiction? Uncertainty and Inaccuracy in Transport Project Evaluation Nicolaisen, Morten Skou Publication date: 2012 Document Version Accepted author manuscript, peer reviewed version Link to publication from Aalborg University Citation for published version (APA): Nicolaisen, M. S. (2012). Forecasts: Fact or Fiction? Uncertainty and Inaccuracy in Transport Project Evaluation. Department of Develpment and Planning, Aalborg University. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research. ? 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Edition (online version) December 2012 © Aalborg University and Morten Skou Nicolaisen Department of Development and Planning, Aalborg University Author: Morten Skou Nicolaisen Supervisor: Petter Næss Co-supervisor: Arvid Strand Cover: Silvia Dragomir Printed by: Uniprint, DK-9210 Aalborg Total pages: 226 Contents PREFACE .......................................................................................................................................................... 1 DANSK RESUMÉ ............................................................................................................................................... 4 ABSTRACT ........................................................................................................................................................ 5 1 INTRODUCTION ....................................................................................................................................... 6 1.1 TRANSPORT PLANNING AND THE NEED FOR APPRAISAL ........................................................................................ 6 1.2 COST-BENEFIT ANALYSES LEAD THE WAY .......................................................................................................... 9 1.3 PROBLEM STATEMENT AND RESEARCH QUESTIONS ........................................................................................... 11 1.4 SUMMARY ............................................................................................................................................... 13 2 BASIC CONCEPTS .................................................................................................................................... 15 2.1 CAUSALITY IN A STRATIFIED REALITY .............................................................................................................. 15 2.2 SOCIAL SCIENCE AND MODELS ...................................................................................................................... 20 2.3 CLASSIFYING UNCERTAINTY IN MODEL-BASED DECISION SUPPORT ........................................................................ 25 2.4 ACCURACY AND THE ROLE OF PLANNING ........................................................................................................ 28 2.5 FOUR STAGE MODELS ................................................................................................................................. 31 2.6 SUMMARY ............................................................................................................................................... 35 3 RELATED WORKS .................................................................................................................................... 36 3.1 POST-AUDITING OF APPRAISAL ..................................................................................................................... 36 3.2 STUDIES OF FORECASTING ACCURACY ............................................................................................................ 40 3.3 SYNTHESIS OF FINDINGS IN PRIOR ART ........................................................................................................... 61 3.4 SUMMARY ............................................................................................................................................... 64 4 METHODOLOGY ..................................................................................................................................... 66 4.1 ADDRESSING THE PROBLEM STATEMENT ........................................................................................................ 66 4.2 DEGREES OF INACCURACY IN FORECASTING ..................................................................................................... 66 4.3 PLANNING IN THE FACE OF UNCERTAINTY ....................................................................................................... 74 4.4 DATA SOURCES ......................................................................................................................................... 78 4.5 SUMMARY ............................................................................................................................................... 80 5 DATA COLLECTION .................................................................................................................................. 81 5.1 DECISION SUPPORT DOCUMENTS .................................................................................................................. 81 5.2 DATABASES .............................................................................................................................................. 84 5.3 QUESTIONNAIRES ...................................................................................................................................... 88 5.4 INTERVIEWS ............................................................................................................................................. 90 5.5 SUMMARY ............................................................................................................................................... 91 6 FORECASTING INACCURACY ................................................................................................................... 92 6.1 FORECASTING ACCURACY ............................................................................................................................ 92 6.2 EXPLORING COMMON PROJECT TRAITS ........................................................................................................ 106 6.3 THE SENSITIVITY OF IMPACT ASSESSMENTS ................................................................................................... 124 6.4 SUMMARY ............................................................................................................................................. 136 7 UNCERTAINTY MANAGEMENT ............................................................................................................. 137 7.1 UNCERTAINTY IN DECISION SUPPORT DOCUMENTS ......................................................................................... 137 7.2 SURVEY RESULTS ON UNCERTAINTY MANAGEMENT ........................................................................................ 143 7.3 INTERVIEWS ........................................................................................................................................... 166 7.4 SUMMARY ............................................................................................................................................. 201 8 CONCLUSION ........................................................................................................................................ 202 8.1 FINDINGS .............................................................................................................................................. 202 8.2 DISCUSSION ........................................................................................................................................... 207 9 BIBLIOGRAPHY ..................................................................................................................................... 216 Preface The work presented in this thesis is not only the result of the three years of laborious studies that is part of doing a Ph.D. The motivation for engaging with the quality of decision support in policy- making came already at the start of my master studies at the Urban Planning and Management programme at Aalborg University. This was in the fall of 2007, where I wrote a report on how to improve the quality of urban spaces together with fellow students Anne Bach and Nina Vogel. During this semester I found myself becoming increasingly concerned with how the quality of both public and private spaces was influenced by