One of the foundational elements for the success of PPPs is the alignment of goals and objectives between the public and private partners. This alignment ensures that both parties are working towards a common purpose, which is essential for the long-term sustainability of the partnership. Strategic Planning is crucial in this context, as it helps in identifying and articulating shared goals, thereby laying a solid foundation for the partnership. According to McKinsey & Company, partnerships that have a clear strategic alignment are more likely to succeed and deliver on their objectives. This involves not only aligning on the end goals but also agreeing on the means to achieve them, including the allocation of resources, responsibilities, and risk-sharing mechanisms.

Furthermore, establishing clear and measurable objectives is paramount. These objectives should be SMART (Specific, Measurable, Achievable, Relevant, and Time-bound) and should be monitored regularly through a robust Performance Management system. This ensures that the partnership remains on track and any deviations are addressed promptly. For instance, the London Underground PPPs, although faced with challenges, highlighted the importance of having clear objectives and a Performance Management framework to monitor and manage the delivery of services.

In addition to strategic alignment and clear objectives, effective Communication plays a critical role. Regular and transparent communication between the public and private partners fosters trust, ensures that all stakeholders are informed and engaged, and helps in managing expectations. This is vital for the long-term success and sustainability of PPPs.

The financial viability of PPPs is another critical success factor. A robust Financial Model that accurately reflects the costs, revenues, financing structure, and economic assumptions is essential. According to PwC, a well-structured financial model can help in identifying potential financial risks and assessing the overall viability of the PPP project. It is important that the financial model is flexible enough to accommodate changes and uncertainties over the life of the partnership.

Risk Management is another key aspect. PPPs inherently involve various risks, including financial, operational, and environmental risks. A comprehensive risk management strategy, which includes the identification, assessment, and mitigation of risks, is crucial. This strategy should be agreed upon by both partners and include mechanisms for risk sharing that are fair and balanced. For example, the Channel Tunnel Rail Link (CTRL) project between the UK and France demonstrated effective risk management, where risks were allocated to the parties best able to manage them, contributing to the project's success.

Ensuring financial sustainability also involves securing long-term financing and having contingency plans in place. This might include establishing reserve funds or having access to additional financing sources, which can provide a buffer against unforeseen financial challenges.

Innovation is a key driver of value in PPPs. Encouraging and fostering innovation can lead to more efficient and effective delivery of services. This requires a culture that supports innovation, including mechanisms for sharing ideas, experimenting with new approaches, and learning from both successes and failures. For instance, the Sydney Metro Northwest project in Australia is often cited as an example where innovation in design and construction techniques led to improved outcomes.

Continuous Improvement is equally important. PPPs should not be static; they need to evolve and adapt over time. This involves regular reviews of performance, processes, and practices, and making adjustments as necessary. Implementing a Continuous Improvement program can help in identifying inefficiencies, reducing costs, and improving service delivery over time.

Finally, the long-term sustainability of PPPs is greatly enhanced by a commitment to Environmental, Social, and Governance (ESG) principles. This includes adopting sustainable practices, ensuring social equity, and maintaining high standards of governance. Such a commitment not only contributes to the project's success but also ensures its acceptance and support from the community and stakeholders.