For a given problem in city logistics, diversity of the stakeholders makes it difficult to consider everyone’s objectives and constraints. Therefore, it is hard to anticipate the impacts of a new regulation. The proposed methodology is based on participatory modelling, where stakeholders share their expertise in order to build a common representation of the problem. In the proposed use case, discussion groups are asked to estimate regulatory impacts on two types of carriers. Following the objective to involve people unfamiliar with modelling techniques, the experimentation aims at testing if interactivity with the model helps as support for discussion.