In our democratic society, how is the right to access information and participate in the preparation of decisions on major projects exercised? How does the exercise of these rights fit into the decision-making process? The answers provided to these questions in the conduct of three sensitive projects, the subject of lively social debate, are described here: the mediation set up in 2017 by the government on the Notre-Dame-des-Landes airport project, the 2019 public debate on the radioactive materials and waste management plan, and the 2023 public debate on the launch of two new EPR2 nuclear reactors at Penly. Michel Badré was involved in the debates on all three projects, in a position of independence from the decision-makers and stakeholders in favor of or opposed to the projects under discussion. What he offers here is personal feedback rather than theoretical reflection. His analysis shows that a shared understanding of the technical and social issues at stake, in all their complexity, makes these debates effective. It takes time, but it's the key to finding solutions that are accepted by society, and that meet the environmental challenges of our time.