State Implementation Plans (SIPs) provide estimates of future emissions and include planned control measures and other components that demonstrate how the area will meet the U.S. EPA’s National Ambient Air Quality Standards (NAAQS) for criteria pollutants to achieve attainment.  In 2013, ACRP published ACRP Report 84: Guidebook for Preparing Airport Emissions Inventories for State Implementation Plans to help airports prepare emissions inventories.  The U.S. EPA regularly updates the NAAQS and sometimes adjusts threshold criteria.  This results in more areas being reclassified with more severe designations.  As a result, more airport improvement projects are facing scrutiny.  Executive Order 12898 (1994) introduced a new impact category that may require modification of the traditional impact analyses used for criteria pollutants, with different spatial, demographic, and geographic considerations; this was reiterated with Executive Order 14096 (2023).  Additionally, since the report’s publication, the use of new models and tools has become standard practice for airport emissions inventory development.

 The objective of this research is to update ACRP Report 84: Guidebook for Preparing Airport Emissions Inventories for State Implementation Plans to reflect the latest in policies and the state of practice.