1999 NEI Methodology (TTI-2001-10)

This Technical Note describes and documents the methods used to develop on?road mobile source emissions inventories for 254 Texas counties to be submitted to the U.S. Environmental Protection Agency (EPA) as the Texas portion of the EPA's 1999 National Emissions Inventory (NEI). This 1999 NEI analysis includes both daily and annual emissions estimates for volatile organic compounds (VOC), carbon monoxide (CO), and oxides of nitrogen (NOx). Methods relating to calculating inventory elements including time periods, seasonal day?of?week vehicle miles traveled (VMT) adjustments, VMT annualization factors, VMT mix, speeds, emissions factors, and the resulting emissions estimates are documented. (This task was revised by verbal agreement with TNRCC's project manager to include all 254 Texas counties rather than the 238 counties called for in the contract. Travel model link?based emissions inventories and associated documentation are being prepared separately for the 16 nonattainment area counties.)