The search for solutions to mitigate collisions between vehicles and animals on roads is urgent, however, given the environmental, economic, and political complexity of this problem, it is essential to strengthen the decision-making process using guidelines and technical standards for the elaboration of studies. One way to accelerate the process of developing evidence-based best practices is through transdisciplinarity and institutional cooperation. The aim here is to present an initiative of collaborative construction of a norm for the development of mitigation plans for animal-vehicle collisions on roads in the state of São Paulo in Brazil. The state of São Paulo has vast experience with carcass monitoring by road inspectors, very focused on user safety. This work is regulated by a normative that provides Criteria for the destination of dead animals on roads (CETESB Decisão de Diretoria 141/2018). Despite this, it still does not have its technical rule for the sampling of roadkill and the preparation of Mitigation Plans. In 2021, a Working Group was created by the state's environmental agency (CETESB) to prepare regulations for the implementation of a Mitigation Plan for Roadkill on State Roads. The meetings take place monthly and include different actors involved in the process of assessing the impact of animal collisions: environmental agency analysts from different departments, professionals from the regulatory agency, companies responsible for the roads (both concessionaires and public), public ministry, and researchers. Every month, an average of 30 professionals get together to discuss the six stages of the Mitigation Plan preparation manual. The stages involve the characterization of the road network, the baseline study of the roadkill and potential areas for connectivity, the identification of priority areas for mitigation, the definition of mitigating measures, the destination of carcasses, and the monitoring of the use and effectiveness of mitigation measures. In all meetings, those involved receive in advance the agenda that will be discussed, and all are invited to send contributions and questions, both asynchronously and during the meeting. The goal is always to reach a consensus on all decisions made, hoping that the process will be more meaningful. The inclusion of representatives from most or all of the sectors involved provides more credibility to the recommendations and decisions. Besides making the process more democratic, participatory construction can act as quality control of the decision process, increase acceptance of the results, and generate mutual learning by creating collaborative networks. Four stages have been discussed so far, and the group is committed to completing the manual by July 2023. It is expected that the result of this effort will qualify and facilitate decision-making, optimizing the implementation of more effective mitigation actions.