A 2002 multi-state accord between NIRPC, SEWRPC, and CMAP, amended in 2008 to include the Southwest Michigan Regional Planning Commission, already exists and has been described as an “historic agreement in which the planning agencies have committed to work together as they consider major environmental and economic issues, enabling planning at the watershed or aquifer scale without the limitation of traditional political boundaries” (NIRPC, 2011). The accord originally led to research and projects related to regional water resource management, for example, the establishment of the Southern Lake Michigan Regional Water Supply Consortium in 2005 (CMAP, 2010b). More recently, the directors of the four constituent regional planning agencies have discussed coordination of projects to develop regional trails, with progress described by CMAP (2010c) in its report on regional greenways and trails in Northeastern Illinois. To facilitate regional co-ordination on transportation, the Tri-State Region would benefit from a long-term, cross-border regional transportation plan.