AEDT’s framework incorporates emissions and dispersion modeling functionality from  the  FAA’s Emissions and Dispersion Modeling System (EDMS). These models are further discussed  within this section.  In 2012, AEDT version 2a (i.e., AEDT 2a) replaced the “legacy” regional noise analysis tool, the  Noise Integrated Routing System (NIRS). 17  As such, the primary purpose of AEDT  2a was to  model the environmental consequences of air traffic airspace and procedure actions designed and implemented by the FAA’s Air Traffic Organization  (ATO). AEDT 2a also  included the capability to assess CO$_{2 }$emissions from aircraft main engines. Of note, AEDT 2a is  the required model for air traffic airspace and procedure action NEPA analyses. 18  AEDT version 2b will replace  AEDT 2a and the legacy airport air q uality and noise analysis  tools - the EDMS and the Integrated Noise Model (INM) . AEDT2b will then become  FAA’s  single environmental assessment tool for air quality and noise for all  projects, including but not  limited to airport and airspace NEPA reviews, General Conformity determinations, Planning studies, and Part 150 Noise Compatibility Programs.  The AEDT user interface and underlying software architecture are distinct from that of EDMS and INM models. AEDT is built on the Microsoft .NET Framework and is capable of  running on Microsoft Windows desktop and server operating systems. It is supported by extensive system of relational databases and an ESRI 19  geospatial capability. Input data are  entered into AEDT using the user interface, an XML -based AEDT Standard Input File (ASIF),  and/or other EDMS/INM model import tools.  Using AEDT 2b, aviation-related emissions inventories can be computed for the EPA criteria air  pollutants (e.g., CO, Pb, NO$_{2}$, O$_{3}$, PM$_{10}$, PM$_{2.5}$, and SO$_{2}$) and their precursors (e.g., NO x  and  VOCs). Sources of airport emissions included in AEDT 2b encompass aircraft, APUs, GSE, and  an array of stationary sources (e.g., boilers, generators, etc.). For this version, the user utilizes the  Motor Vehicle Emission Simulator  (EPA’s MOVES) 20  model independently of AEDT 2b obtain the necessary data for computing motor vehicle emissions.  Dispersion modeling can also be conducted within the AEDT interface, based on the results of  the emissions inventory and supplemented with meteorological data and the definition receptor sets. Once the necessary data are inputted to AEDT, AEDT internally calls for the EPA  AERMOD modeling system to perform the specified dispersion calculations. The resulting  17  FAA,  Guidance on Using AEDT 2a to Conduct Environmental Modeling for FAA Air Traffic Airspace and  Procedure Actions , March 2012, http://www.faa.gov/air_traffic/environmental_issues/media/Memo-AEE- 400_GuidncMem4_UsingAEDT2a_EnviroModeling_21MAR2012.pdf.  18  77 FR 18297 - Air Traffic Noise, Fuel Burn, and Emissions Modeling Using the Aviation Environmental Design  Tool Version 2a,  http://www.gpo.gov/fdsys/granule/FR-2012-03-27/2012-7354/content-detail.html.  19  ESRI's GIS (geographic information systems) mapping software enables the visualization of geographic data,  http://www.esri.com/.  20  EPA, MOVES (Motor Vehicle Emission Simulator),  http://www.epa.gov/otaq/models/moves/index.htm#generalinfo.  5.1.2.  AEDT Usage for Air Quality Assessments  5.1.1.  AEDT Development and Architecture  Aviation Emissions and Air Quality Handbook  31$_{ }$