Governance, contracts, and culture: A triadic approach to megaproject performance

Despite their transformative ambitions, transport megaprojects, such as high-speed rail systems, often underperform. This study investigates the California High-Speed Rail Project (CAHSRP) using a critical realist methodology and a Context-Mechanism-Outcome (CMO) framework to examine how governance, contracts, and culture interact to shape project performance. We propose a novel triadic model that conceptualises performance as an emergent property of the dynamic interplay among these three institutional mechanisms. Drawing on thirteen semi-structured interviews and extensive secondary data, we identify key mechanisms, such as decision-making structures, contractual strategies, and trust-building practices, which influence cost overruns and schedule delays. The findings reveal that improving contractual design alone is insufficient; instead, outcomes are shaped by the co-evolution of formal and informal mechanisms within complex institutional contexts. This study contributes to project management theory by integrating governance, contractual, and cultural dimensions through a critical realist lens and offers practical guidance for managing infrastructure megaprojects in uncertain environments. The insights have implications for policymakers and practitioners seeking more holistic and adaptive approaches to megaproject delivery. • The triadic model links governance, contracts, and culture in megaprojects. • Uses critical realism and CMO to study the California High-Speed Rail Project. • Shows performance emerges from co-evolving institutional mechanisms. • Culture reframed as active force shaping project outcomes. • Offers guidance for adaptive governance and relational contracting.