“Conformity” refers to a regulatory requirement in which regional and state transportation plans must show that they are consistent with existing air quality goals. Transportation and pollution modeling, consultation between agencies, and public participation define the process. A transportation plan demonstrates “conformity” when the U.S. Department of Transportation reviews and approves the modeling and plans as meeting all regulatory requirements. A new conformity determination must be performed any time a transportation plan is amended in a significant manner, when a region’s or state’s air quality goals change, and/or every four years. The most recent conformity determination for the Houston-Galveston-Brazoria region was performed in August 2007. Amendments were proposed in October 2007, and are still in the process of being reviewed and approved.