The model addresses investment in new assets or significant, predefined refurbishment of existing assets in the early stages of the project, but it does not address on-going asset maintenance or replacement. This is typically a project company risk where the project company provides asset management functions. While this risk is an important aspect of a PPP project, it was considered so common that it was not included as a separate category to avoid diluting its relevance. Providing a separate category for this function was considered insufficiently critical when balanced against its complexity and the underlying pursuit of simplicity.