The Conformity Rule, adopted in November 1993, by the U.S. Environmental Protection Agency (USEPA) under the requirements of Section 17(c)(4) of the Clean Air Act, establishes strict procedures for determining conformity of transportation plans to state air quality management plans. Conformity requirements apply to all transportation plans, programs, and projects, funded or approved under title 23 U.S.C. or the Federal Transit Act. The Conformity Rule requires that transportation planning agencies apply transportation demand and emission models to demonstrate that transportation plans and all projects contained in a plan will not exceed the allowable emissions budget established in the air quality management plan and will not cause a violation of local air quality standards. This project was undertaken by the Institute of Transportation Studies at Davis (ITS-Davis) for the California Department of Transportation (Caltrans). ITS-Davis researchers were asked to undertake this project for three reasons to: 1) provide objective opinions from individuals outside the purview of agencies responsible for implementing the Rule; 2) identify and discuss technical issues associated with emissions modeling that should be considered in implementing the Rule; and 3) explore potential institutional conflicts that may arise in implementing the Rule. The primary goal of the overall project was to develop a conformity modeling protocol for project analysis. Before the technical modeling guidance document could be developed, the research team undertook a comprehensive review of the Rule and applicable conformity literature to determine where, when, and under what conditions, conformity findings for local projects must be made. The first section of this policy document outlines the conformity process and the specific requirements that must be met in making conformity determinations under the CAA and the subsequent conformity rules promulgated by the USEPA and the USDOT. The second section of this document addresses NEPA/CEQA requirements and provides guidance that will aid in understanding how the conformity process is interrelated with the environmental impact assessment process. The third section of the report addresses the importance of a comprehensive and stringent adherence to the mandates of both the Rule and the NEPA/CEQA. In the final section of this policy report, the findings for the technical modeling studies are summarized. This report concludes with a summary of the relevant policy issues associated with project assessment under the Rule.