NCHRP Project 25-17 assessed the expected effects of the new NAAQS for ozone and PM on transportation planning, the transportation project development process, and the implementation of transportation system improvements. More specifically, the research project examined and assessed the probable impacts of the new NAAQS on conformity; the transportation planning process; the project development process; the NEPA process; and the potential contribution of air quality attainment by transportation control strategies, transportation systems development, and mobile source technology improvements.

The purpose of this task is to re-evaluate the conclusions of the Final Report developed under NCHRP Project 25-17 based on new emission factor models, new rules, and impending implementation guidance that were not available during the original research effort. The emissions and air quality modeling results will be re-evaluated based on the new MOBILE6 and EMFAC models that were not available in time to be incorporated into the Project 25-17 efforts. The effects of new rules, such as the Heavy Duty/Low Sulfur Diesel Rule, that were not in place when the previous analysis was performed will also be included. In may also be important to factor in our current understanding of emerging rules (e.g., Clear Skies Initiative, Non-Road Engine Rules, etc.). The implications of the new models and new rules on SIP development and future conformity determinations will be determined. Ultimately, the conclusions of Project 25-17 will be confirmed or revised accordingly.

In addition, it is anticipated that EPA will publish Draft Implementation Guidance for the 8-hour ozone standard in the near future. For example, areas that currently attain the 1-hour ozone standard but may violate the 8-hour ozone standard may opt-in to an 8-hour ozone FlexPlan or Early Action Compact (EAC). This program would accelerate the implementation of controls to achieve attainment by 2007 in return EPA would not designate the area as 8-hour ozone nonattainment which would have far reaching effects on the regions transportation planning. The project team will evaluate the draft policy and analyze any impacts on the conclusions of Project 25-17. The results of the supplemental evaluation to incorporate more recent information will further enable the transportation community to: (1) assess the expected effect of the new NAAQS and (2) provide reasoned and efficacious input into the regulatory process.