The complexity inherent in large infrastructure projects often results in project delays, cost overruns, and failures. Managing this complexity, particularly in the construction industry, is essential for improving project outcomes. This research aims to contribute to the body of knowledge on project complexity by exploring the interdependencies between elements of complexity in infrastructure projects. Using a case study of the Zuidas-Tunnels project in the Netherlands, this study applies a hybrid fuzzy method to identify the most significant elements contributing to project complexity and analyze their interdependencies.

A literature review and exploratory interviews were conducted to assess existing complexity management strategies. The research utilizes the TOE (Technical, Organizational, Environmental) framework to categorize 47 complexity elements. The Decision Making Trial and Evaluation Laboratory (DEMATEL) and Interpretive Structural Modelling (ISM) methods were applied to model and analyze these interdependencies between these elements.

The results reveal that understanding the relationships between complexity elements is crucial for effective complexity management. This insight can help project managers develop more targeted strategies to mitigate complexity's impact, thus improving the performance of large-scale infrastructure projects. The study concludes by recommending that such methods be integrated into project management practices for dynamic assessment and management of complexity throughout the project lifecycle.