Optimal risk allocation for private public partnership transportation infrastructure projects in Australia

Public–Private Partnerships (PPPs) have been widely adopted as a key contractual model for delivering public infrastructure globally. Recently, there has been a shift toward mega-scale PPP transportation infrastructure, exemplified in Australia by the Sydney Metro project. This study investigates critical risks commonly encountered in such projects and proposes optimal strategies for their allocation. A qualitative approach was adopted, comprising an extensive literature review and expert interviews. The study identifies 22 risks associated with mega PPP infrastructure projects, categorized into two groups: those associated with the project lifecycle stage (static risks) and those related to their inherent nature (dynamic risks). In the former, key risks include challenges from brownfield environments, demand/patronage uncertainty, and operation and maintenance performance due to facility conversion and advanced technologies. In the latter, major risks involve interfacing issues with multiple contractors, Covid-19 disruptions, and public opposition. The public sector tends to retain dynamic risks, leveraging policy settings to minimize costs and delays, and address public concerns. Conversely, the private sector takes on risks tied to delivery, operation, and maintenance, enabling revenue growth and reputation building. Risks related to limited PPP experience and complex contract design are best managed through collaboration.