Long-term leases of existing transportation assets have tended to dominate the PPP discourse in the United States, largely due to the highly publicized and controversial leases of the Chicago Skyway and the Indiana Toll Road. Although some policymakers have come to associate PPPs with this type of project, in fact, a wide range of possible PPP projects exists. PPP projects differ based on 1) the "mission," or the kind of facility or public service that is the focus of the project; 2) the "method," or the project delivery model; and 3) the "money," or the source of financing (Figure 1).10

Figure 1. PPP Project Components11