A Multilevel Perspective on Governance and System Integration in Large‐Scale Civil Infrastructure Systems: The Cases of Crossrail and HS2

This study explores governance and systems integration challenges in complex infrastructure megaprojects through a comparative qualitative analysis of the UK's Crossrail and High Speed 2 programs. Drawing on project documentation and interview evidence, it examines how strategic pressures, institutional governance arrangements, and project‐level delivery practices interact to shape project outcomes. The analysis uses the multilevel perspective as an analytical lens to identify 10 operational guiding principles that reflect recurring integration risks, governance misalignments, and organizational constraints. The Crossrail case highlights the importance of early and coordinated systems integration, while the HS2 case highlights the difficulties of long‐term planning in the face of changing political and financial conditions. Rather than proposing prescriptive solutions, the study offers transferable insights into how governance capacity and cross‐level alignment influence delivery robustness in complex infrastructure programs.