It is important to define the term infrastructure since there are many different types, not all of which are appropriate for private funding. From a financing perspective, infrastructure opportunities are usually capital intensive, there is a tangible asset to operate and maintain, and the asset is expected to generate cash over the long term. Yet, there are other important distinctions from a financing perspective such as the type of project (i.e. social vs. economic infrastructure), contractual approach (e.g. partnership, concession, privatization etc.), phase of physical development (i.e. greenfield vs. brown-field), and stage of market development (e.g. new and innovative vs. new and tested). These characterizations more precisely address the chief concerns of private financiers as to whether they will achieve forecasted returns and the likelihood of loan repayment. A focus just on greenfield or brownfield designations or sector (e.g. energy vs. transportation) is too limited from a financing perspective.