Limits to Predictability
GEENHUIZEN M S V, Delft University of Technology, ZUYLEN H J V, Ministry of Transport and NIJKAMP P, Free University of Amsterdam, The Netherlands
Prediction of the future has always been a major prerequisite for decision making in policy. It enables policy makers to anticipate coming events and to select policy measures. However, when one moves beyond simple projects and short-range issues, predict
Prediction of the future has always been a major prerequisite for decision making in policy. It enables policy makers to anticipate coming events and to select policy measures. However, when one moves beyond simple projects and short-range issues, predicting the future becomes increasingly difficult. For example, predictions on the growth of second (third) airports in large metropolitan areas often prove wrong (de Neufville, 1997). The same holds for various other large ir~astmcture projects, such as the metro-system BART in the San Francisco area (Hall, 1990). In this particular case, there has been a failure to understand the behaviour of travellers.
There is now an increasing awareness of the ill-predictability of the future and its implications for policy making (el. Ester et ai., 1997; van Geenhuizen and Nijkamp, 1998; Nijkamp, 1996; R_MNO, 1995; Stacey, 1992; Wynne, 1992). Various options are available in responding to ill-predictability and concomitant uncertainty. One may reduce uncertainty to an acceptable level before decisions are taker~ or refrain from new decision making and postpone major decisions. An interesting but still uncommon option is to take advantag e of uncertainty and explore emerging opportunities, and possibly reach a higher level of creativity in finding solutions.
It is also increasingly realised that ill-predictability is a comprehensive phenomenon that manifests itself at different time scales and spatial scales. It runs from the daily management of road traffic to long-term forecasts of travel behaviour, and from particular sections of local roads to traffic systems on a European level. This paper discusses the results of an exploratory study on the limited possibilities to predict the future and the way in which policy makers in transport may cope with this (van Geenhuizen et al., 1998). The study is based on a scan of the literature and on in-depth interviews with selected policy makers and experts. First, the paper explores the different types and sources of uncertainty in transport policy. It particularly addresses two opposing views in policy making basedupon a different appreciation of uncertainty. In order to find a rich picture of opportunities to cope with unccnccainty, the paper explores responses to uncertainty from both policy views. Accordingly, it discusses participatory methods, scenario development, and improved modelling. The paper concludes with a number of interesting lines for future research.
Association for European Transport