Office of Transportation and Air Quality U.S. Environmental Protection Agency NOTICE

It is intended to present technical analysis of issues using data that are currently available. The purpose in the release of such reports is to facilitate the exchange of technical information and to inform the public of technical developments which may form the basis for a fi nal EPA decision, position, or regulatory action. Purpose The purpose of this report is to discuss the methodology and data that the Environmental Protection Agency (EPA) uses in the NONROAD2005 model to allocate equipment populations from the national to the state and county level. Background EPA has developed a national nonroad air emissions inventory model called NONROAD. This model provides a tool for EPA, States, regional air pollution organizations, and local air pollution control agencies to use in estimating pollution from nonroad vehicles and equipment for State Implementation Plans (SIPs), as required by the 1990 Clean Air Act Amendments, and other regulatory needs. With some exceptions, the model uses national engine population or sales data from Powe