The Environmental Protection Agency promulgated a new standard for fine particulate air pollutants (PM 2.5) and designated PM 2.5 air quality non-attainment areas. These non-attainment areas, some of which were in attainment prior to the establishment of new standards, must have long range transportation plans and Transportation Improvement Programs (TIP's) that meet conformity requirements by April, 2006. States that have air quality non-attainment areas must spend their CMAQ funding on transportation projects in air quality non-attainment areas. Air quality non-attainment areas are struggling to identify CMAQ-eligible investment strategies to address the new PM 2.5 requirement. SAFETEA-LU amends Title 23 to make transportation investments that contribute to PM 2.5 attainment and maintenance eligible for CMAQ funds. This study will identify transportation investments for achieving PM 2.5 attainment, regardless of current eligibility and rank those investments based on relative cost effectiveness. For each type of investment, the study will analyze the technical, statutory, regulatory, or administrative impediments to implementation.