Comparison of cost and schedule performance of large public projects under P3 and traditional delivery models: a Canadian study

摘要

Cost overrun and schedule delay are pervasive in large public infrastructure projects in Canada and there is an ongoing debate over the root causes of these delivery risks and how best to mitigate them. Since public-private partnerships (P3s) have been long touted as an effective mitigating measure, this study aimed to provide comparative empirical evidence to explore this claim. By collecting cost and schedule data at three key milestones (decision to build, contract awarding and substantial completion) from 39 traditional projects and 27 P3 projects across Canada between 2004 and 2016, the study develops an innovative longitudinal profiling approach to inform the debate about the causes of cost overruns in large public projects. Statistical analyses of the collected data unambiguously demonstrate that P3s outperform non-PS traditional delivery models during the construction stage in both cost overrun and schedule delay. However, substantial budget underestimation is found in the strategic decision-making process of both models of project delivery. Results from the study also provide solid objective grounds for the development of advanced value-for-money assessment methodology.