The Delphi method is a process used to arrive at a collective, aggregate group opinion or decision by surveying a panel of experts. This concept was developed by the RAND Corporation for the military in order to forecast the effects of new military technology on the future of warfare, and then continued to make multiple practical applications of this method (Dalkey & Helmer, 1963). The Delphi methodology is based on a repetitive interview process in which the respondent can review his or her initial answers and thus change the overall information on each topic (Hsu & Sandford, 2007). This presupposes that the participants will be willing to not only give answers on the topics but also to repeat the interview in possibly more than two cycles.
Within LEVITATE, the Delphi method is used to determine all impacts that cannot be defined by the other quantitative methods (traffic microsimulation/system dynamics). Initially, a long list of experts were identified for each use case, and contacted via an introductory mail asking them to express the willingness of participation. Those who responded positively (70 experts) participated in the main Delphi process.
If you want to know more about the Delphi studies conducted in the frame of Levitate, including the list of impacts and result introduction to the Policy Support Tool, read our article from the National Technical University of Athens.