Decision makers like to know what the future will bring, in order to anticipate problems, assess the quality of their decision and tailor their decisions such that optimal impacts can be expected. Uncertainty about the future is reduced by all kinds of techniques ranging from extrapolation to sophisticated predictive modelling. A study has been made on the limitations of the possibility to predict the future and on the impact of this limitation on decision making. Ill-predictability can be analysed in the following categories: (1) ill-predictability of the dynamics of the transport system; (2) the complexity of the interaction between the transport system and its environment, including the ill-predictability of the dynamics of the environment; (3) lack of knowledge about the transport system; (4) human behaviour; and (5) evolution of political values, visions and goals. The paper discusses the relevant processes which are ill-predictable, the reasons of ill-predictability and its consequences. Ill-predictability of the future can lead to a different way of policy making and implementation. Furthermore, there are new approaches possible to reduce uncertainties.
Abstract