A building block approach to simulation uses modules that are easily reusable and therefore speed up the simulation process. The authors assume that this approach can enhance complex decision making between stakeholders on infrastructure planning and design. The authors combined insights from process management and a simulation building block approach into an experimental interactive decision-making procedure and developed a simulation building block tool. The authors tested the procedure and the tool in the game CONTAINERS ADRIFT. Evaluation results indicate that the simulation tool is fast and easy to work with and that the combination of simulation building blocks and process management contributes to the quality and process of negotiation and generates mutual understanding.