Scenario development in transport studies: Methodological considerations and reflections on delphi studies

Developing scenarios for future sustainable transport solutions is challenging as there are many uncertainties to consider. One method used is the Delphi method. The purpose of this paper is to investigate how the Delphi method has been used in transport scenario studies and to discuss the method's methodological considerations and future potential in transport studies. The review is based on publications within transport research in which the Delphi method is used to develop future scenarios. Reflections and discussions on the Delphi method are presented and highlight three aspects: context, consensus and combining methods. By sampling experts from a wide range of backgrounds and organisations, a number of differing views are incorporated in the studies. Researchers need to consider the context of the selected experts and how it affects the possibilities for consensus. Reaching consensus may limit exploration of new innovative and radical ideas. Instead of aiming for consensus, this paper points out that a dissensus Delphi can be used in order to explore divergent ideas about the future. Finally, the Delphi method can be combined with quantitative as well as qualitative methods.