Small urban and rural areas that are required to conduct conformity analysis typically face many challenges in conducting the regional emissions analysis: limited data on VMT and speeds, lack of a travel demand forecasting (TDF) model, and often limited staff expertise in emissions modeling. While large metropolitan areas generally have advantages in terms of resources, data, and tools, it is important to recognize that valid methods are available to conduct the regional emissions analysis in small urban and rural areas.
This document provides a sampling of methodologies and adjustment techniques for developing estimates of VMT and speeds, the two key inputs required for emissions modeling. It also describes other factors that influence emissions factors, and highlights approaches for using local data rather than MOBILE6 model defaults. Each option has certain advantages and limitations. There is no "one-size fits all" approach that should be applied in all areas. Areas subject to conformity should identify what methods are most appropriate to their region through the interagency consultation process. The selected methods should reflect data availability and local conditions. Other options beyond those profiled in this report may also be available, and regions should explore other possibilities.
