Exploring the complexity of highways infrastructure programmes in the United Kingdom through systems thinking

In this study, we seek to conceptualise multi-dimensional impacts of infrastructure investment through case studies of three nationally significant highways programmes in England. We use system thinking principles to characterise socioeconomic and policy impacts that may emerge from the interconnectedness of system variables. We consider three 'complex infrastructure programmes' in the National Highways portfolio; the A303 Stonehenge Tunnel, the A66 Trans-Pennine upgrade and the Lower Thames Crossing (LTC) and illustrate the interdependencies that may be present within and between these programmes using causal models. We identify a set of commonalities between the three programmes, with indications towards potential mechanisms for facilitating economic growth in disparate regions where timely implementation of efficient policies may be achieved. Moreover, we evidence that evaluating impacts through segmented areas of focus such as social, economic and policy may not adequately portray the real impacts of infrastructure investment in a comprehensive way. This research justifies the importance of understanding infrastructure projects as interconnected, complex systems that may deliver desired benefits in a non-linear and highly emergent way. We conclude with a proposition that understanding the characteristics of the larger infrastructure system-of-systems, is crucial to unlocking added value and realising long-term benefits of highways infrastructure investment.