Performance and efficiency diffusion of us surface transportation public-private partnerships

With successes and attritions, the US transportation industry has implemented public-private partnership (P3) projects for over 3 decades. However, performance inquiries of P3 have not kept up with its development, showing mixed results. The predominantly cross-sectional approach may mask a certain within-project effect on cost and time certainty. Using 133 major transportation projects from the Information Source for Major Projects database, the authors performed piecewise linear growth curve modeling to parse out variation attributable to delivery method and variation attributable to that within-project effect, conveniently termed efficiency diffusion. The results revealed that P3 is on par with design-bid-build (DBB) in terms of cost certainty, but performs better in terms of time certainty. In contrast, efficiency diffusion from P3 is evident in cost but not in time. In other words, P3 creates a spillover and internalization of technical and managerial innovations, inducing cost savings. This is the first longitudinal study to reconcile previous cross-sectional efforts, and showed P3's better time certainty compared with DBB using project-level data in the US while confirming the delivery method's cost-saving spillover effect, effectively raising the bar.